A Brief Commentary on the Holy Scriptures; Tree of Life Version(TLV).

Seeing Scripture through Jewish eyes.

A song: a psalm of Asaph.
God, do not keep silent.
Do not hold Your peace, O God.
Do not be still.
For look, Your enemies make an uproar.
Those who hate You lift up their head.
They make a shrewd plot against Your people,
conspiring against Your treasured ones.
“Come,” they say, “let’s wipe them out as a nation!
Let Israel’s name be remembered no more!”
For with one mind they plot together.
Against You do they make a covenant.

                                                                                                                        Psalm 83: 1-5

 

Are you looking for a brand-new Bible experience? Are you searching for a translation of the Bible that restores some of the Hebrew names and terminology found in the original manuscripts? Perhaps you are looking for a Bible that will help you rekindle an interest in the sacred words of Scripture seen from a Messianic Jewish perspective? If so, I have just the recommendation for you; enter the Tree of Life Vesion(TLV).

The brain child of this ambitious project was Daniah Greenberg and her Rabbi husband, Mark Greenberg, who assembled a cadre of Messianic Jewish Bible scholars to create an all-new translation of the Holy Scriptures that gives the reader a solid flavour of the original Hebraic overtones of the Bible, with a decidely Jewish accent. But it was no small feat, given the proliferation of English Bible versions flooding the global market. Daniah had the courage and conviction to raise the funds to pay for soild scholarship within the Jewish cultural tradition, which culminated with the first edition of the TLV Bible in 2011. Daniah Greenberg now serves as President of the Messianic Jewish Family Bible Society. Greenberg is also CEO of the newly established TLV Bible Society.

It pays to remember that all the Biblical writers, with the possible exception of the author of the Book of Job, were Jews. Jesus Christ was Jewish. The earliest Christian meetings took place in synagogues and despite the attendant evils of anti-semitism throughout history, and its giving rise to unbiblical ideas such as replacement theology,  it is undoubtedly the case that unique insights into much of the Biblical narrative has come from the Jewish mindset. Seen in this light, it is not at all surprising that a new Bible translation made by the original people to which the Lord of all Creation first appeared should find a place on the bookshelves of many Christians in the 21st century.

The first thing you will notice about the TLV is the unfamiliar ordering of the books of the Bible, which have been re-presented in the order rendered in the Jewish tradition, which Christians refer to as the Old Testament. In Jewish parlance, these are the books of the Tanakh.

As you can see from the table of contents below, the Tanakh is further divided into three sections; the Torah (Law of Moses or Pentateuch), the Neviim (The Prophets) and the Ketuvim (The Writings).

 

The unique ordering of the books of the Old Testament(Tanakh), as experienced by Orthodox Jews.

The books of the New Testament(Good News) are presented in their traditional order. The reader will note that the Book of James is titled ‘Jacob,’ and Jude is titled ‘Judah, which  represent their transliterated Jewish names.

The New testament books are presented in their traditional order, with two transliterated names, Jacob(James) and Judah(Jude).

A sizeable number of words are presented in the original Hebrew. For example, YHWH God’s covenant name, is often referred to as Adonai,  but also as Elohim (Creator). Jesus is denoted as Yeshua, Mary(the mother of Jesus) is given her original name, Miriam; Spirit is presented as Ruach, the Levitical priests, Kohanim, the children of Israel, B’nei-Israel and Sabbath is translated as Shabbat. All Hebrew terminology can be referenced at the back of the Bible in the form of a tidy glossary. There is even a section which helps the reader pronounce these Hebrew words correctly. That said, once you get into the TLV, most of the terms sink in very easily and naturally and so provide the reader with an education in basic Hebrew religious terminology. The addition of original Hebrew words also adds to the poetic beauty of the language of the Scriptures, which are readily appreciated while reading through.

Each book of the Holy Scriptures is accompanied by a short introduction written by Messianic Jewish scholars, which provides a concise overview of the most important ideas developed in the texts. The translators intentionally chose to produce a translation that is at once respectful to more traditional translations of the Bible such as the Authorized King James Version (KJV), and more modern translations such as the English Standard Version (ESV) and New American Standard Bible (NASB), retaining some classic Biblical terminology such as “Behold“, “lovingkindness” and “Chaldeans.” For example, in the opening verses of the Book of Esther, the TLV refers to the Babylonian King as Ahasuerus and not Xerxes ,as you will find in looser translations such as the NIV and NLT.

This is what happened in the days of Ahasuerus, the Ahasuerus who reigned over 127 provinces from India to Ethiopia.

Esther 1:1

In keeping with the original customs of the first Christians, the word ‘baptism‘ does not appear in the TLV, being replaced by the more appropriate term, ‘immersion.’ This is entirely justified as infant baptism was not practiced by the earliest followers of Yeshua. Consider this passage from Acts 2;

Peter said to them, “Repent, and let each of you be immersed in the name of Messiah Yeshua for the removal of your sins, and you will receive the gift of the Ruach ha-Kodesh.

Acts 2:38

John the Baptist is likewise referred to as “John the Immerser”

Unlike virtually all other Bibles in the English language, the Adversary’s name is presented in lower case, ‘the satan‘; a most appropriate demotion to honour the ‘father of lies.’ Consider, for example, the opening passages of the Book of Job:

One day the sons of God came to present themselves before Adonai, and the satan also came with them.  Adonai said to the satan, “Where have you come from?”

The satan responded to Adonai and said, “From roaming the earth and from walking on it.

Adonai said to the satan, “Did you notice my servant Job? There is no one like him on the earth—a blameless and upright man, who fears God and spurns evil.”

Job: 1:6-8

Another interesting aspect of the TLV is that it quite often departs from the usual preterite, or imperfect tense one normally experiences in traditional translations. Consider this passage from the Gospel of Matthew Chapter 4 in the NASB:

Again, the devil took Him to a very high mountain and *showed Him all the kingdoms of the world and their glory;

Matthew 4:8

Now consider the same passage in the TLV:

Again, the devil takes Him to a very high mountain and shows Him all the kingdoms of the world and their glory.

Matthew 4:8

These occasional departures add to the immediacy of the situation as if it were happening right now! This is a powerful linguistic tool that the TLV scholars used to evince the poignancy of certain passages of Holy Scripture.

The poetic books of the Holy Scriptures, such as the Psalms, are most beautifully rendered and retain traditional  terms like Selah (an uncertain word thought to refer to an interlude in a musical performance). Consider, for example, Psalm 24 in the TLV:

A psalm of David.
The earth is Adonai’s and all that fills it—
the world, and those dwelling on it.
For He founded it upon the seas,
and established it upon the rivers.
Who may go up on the mountain of Adonai?
Who may stand in His holy place?
One with clean hands and a pure heart,
who has not lifted his soul in vain,
nor sworn deceitfully.
He will receive a blessing from Adonai,
righteousness from God his salvation.
Such is the generation seeking Him,
seeking Your face, even Jacob! Selah
Lift up your heads, O gates,
and be lifted up, you everlasting doors:
that the King of glory may come in.
“Who is this King of glory?”
Adonai strong and mighty,
Adonai mighty in battle!
Lift up your heads, O gates,
and lift them up, you everlasting doors:
that the King of glory may come in.
“Who is this King of glory?”
Adonai-Tzva’ot—He is the King of glory! Selah

Psalm 24

 

The reader of the TLV Holy Scriptures will note that the word “church” does not appear in this translation. Instead, the scholars chose to use the words “Messiah’s community.” This is an acceptable change, as the word they were probably translating was the Greek term ecclesia, which appears in the New Testament 115 times and was often associated with a civil body or council summoned for a particular purpose. The nearest the Greek language gets to “church” is kuriakos, which is best understood as “pertaining to the Lord,” which probably morphed into the Germanic “Kirche” or “Kirk,” which is still used in northern England and Scotland to this day.

An amusing aside: Has anyone ever referred to Kirk Douglas as ‘Church Douglas’, who just happens to be an orthodox Jew?

These translative nuances matter little in the scheme of things however. Acts 11 provides a good illustration of these translation choices:

Then Barnabas left for Tarsus to look for Saul, and when he had found him, he brought him to Antioch. For a whole year they met together with Messiah’s community and taught a large number. Now it was in Antioch that the disciples were first called “Christianoi.”

Acts 11:25-26

Note also that the TLV translation team used the Greek term for Christians, ‘Christianoi‘. This is also perfectly acceptable, as there was no Hebrew word for ‘Christian’ in those early days.

The scholars who created the TLV chose to use the latest manuscript evidence, which included much older texts found in the modern era compared with the King James or New King James, for example(which are based on the Textus Receptus). It thus follows a similar translation ethos to other popular Bibles in the English language such as the NIV and ESV.  On the spectrum of modern English Bible translations, which vary from the highly literal, so-called ‘word for word’ renderings, through the less literal ‘thought to thought’ translations, I would categorise the TLV as adopting a ‘middle of the road’ approach. Perhaps the best way to illustrate this is to look at the same passage of Scripture in a few translations. Consider, for example, the highly literal NASB rendition of Matthew 9, verses 1 through 8:

Getting into a boat, Jesus crossed over the sea and came to His own city. And they brought to Him a paralytic lying on a bed. Seeing their faith, Jesus said to the paralytic, “Take courage, son; your sins are forgiven.” And some of the scribes said to themselves, “This fellow blasphemes.” And Jesus knowing their thoughts said, “Why are you thinking evil in your hearts? Which is easier, to say, ‘Your sins are forgiven,’ or to say, ‘Get up, and walk’? But so that you may know that the Son of Man has authority on earth to forgive sins”—then He said to the paralytic, “Get up, pick up your bed and go home.” And he got up and went home. But when the crowds saw this, they were awestruck, and glorified God, who had given such authority to men.

Matthew 9:1-8(NASB)

 

Next consider the TLV equivalent:

After getting into a boat, Yeshua crossed over and came to His own town. Just then, some people brought to Him a paralyzed man lying on a cot. And seeing their faith, Yeshua said to the paralyzed man, “Take courage, son! Your sins are forgiven.” Then some of the Torah scholars said among themselves, “This fellow blasphemes!” And knowing their thoughts, Yeshua said, “Why are you entertaining evil in your hearts? For which is easier, to say, ‘Your sins are forgiven,’ or to say, ‘Get up and walk’? But so you may know that the Son of Man has authority on earth to pardon sins…” Then He tells the paralyzed man, “Get up, take your cot and go home.” And he got up and went home. When the crowd saw it, they were afraid and glorified God, who had given such authority to men.

Matthew 9:1-8(TLV)

 

Finally, consider the same passage from a thought for thought translation like the NIV:

Jesus stepped into a boat, crossed over and came to his own town. Some men brought to him a paralyzed man, lying on a mat. When Jesus saw their faith, he said to the man, “Take heart, son; your sins are forgiven.” At this, some of the teachers of the law said to themselves, “This fellow is blaspheming!” Knowing their thoughts, Jesus said, “Why do you entertain evil thoughts in your hearts? Which is easier: to say, ‘Your sins are forgiven,’ or to say, ‘Get up and walk’?  But I want you to know that the Son of Man has authority on earth to forgive sins.” So he said to the paralyzed man, “Get up, take your mat and go home.” Then the man got up and went home.  When the crowd saw this, they were filled with awe; and they praised God, who had given such authority to man.

Matthew 9:1-8(NIV)

I think it is reasonable to conclude that the TLV is a good compromise between both translation philosophies, distinguishing itself by means of introducing some Hebrew words and names but also in the way that the translators have chosen to alter the tense of some passages, as discussed previosuly.

The TLV  also follows many of the newer Bible versions in adopting a more gender neutral approach to terms such as ‘Brethern’ or ‘Brothers’. For example, the TLV renders Galatians 1:11 thus:

Now I want you to know, brothers and sisters, that the Good News proclaimed by me is not man-made.

Galatians 1:11 (TLV)

Compare this to the more conservative ESV:

For I would have you know, brothers, that the gospel that was preached by me is not man’s gospel.

Galatians 1:11 (ESV)

And the NIV:

I want you to know, brothers and sisters, that the gospel I preached is not of human origin.

Galatians 1:11(NIV)

Some commentators have expressed concern that the Bible should never be altered so as to express political correctness, as in this case, where ‘brothers’ is altered for the sake of inclusiveness to read, ‘brothers and sisters.’ I understand their concerns but I have no strong opinion either way on this issue, so long as the context of the particular verse is not altered.

The TLV does have a couple of errors which I picked up while reading through the translation. The first appears in Jeremiah 34:14

At the end of seven years you are to set free every man his brother that is a Hebrew who has been sold to you and has served you six years; you are [to] let him go free from you.’ But your fathers did not obey Me, nor inclined their ear.

I have inserted the missing word in bold brackets that makes the sentence comprehensible.

In addition there is a printing error in my Large Print Personal Size TLV on page 902 and 903, the heading of which reads “Obadiah 9” and “Obadiah 1,” respectively. Since these headings are meant to illustrate the chapter numbers, they are clearly unecessary as the Book of Obadiah only has a single chapter.

The typographical error niggled me at first (as an avid reader, I’m very tolerant of typos in general but view Holy Scripture in a more exalted light), but I understand that these things happen. I have written to the TLV Bible Society informing them of these issues which I hope they will be able to resolve in due course.

Some comments on the physical presentation of the TLV Holy Scriptures

The author’s TLV large print copy of the Holy Scriptures.

I was very impressed with the quality of the giant print personal size TLV that I acquired back in January 2018. It has a beautiful leathertex cover, which is soft and durable. Indeed, the current selection of faux leather Bibles(in many translations)are amazing value for money, and are superior to the cheap, bonded leather found on premium Bibles just a decade ago. The TLV also has a smyth-sewn binding for greater durability even with prolonged use.

The Personal Size Giant Print TLV is about 9 inches long and 2 inches thick.

It has a paste-down liner, a highly readable 12.5 font size, beautiful gold gilded pages and comes with a single ribbon marker. I especially like the paper used by Baker Books(the publisher of the TLV), which is a more creamy white than the usual white pages seen n many other of my Bibles.As seen below, the text is presented in a double column format and has a generous number of cross-references. The text is line matched and shows minimal ghosting, which annoys some people more than others.

The paper in the TLV is an off white(creamy), the text is double columned, shows little bleed-through, with clear 12.5 sized font.

The back of the TLV has an extensive concordance, a short glossary explaining the Hebrew terms used in the translation, as well as a short section of prayers (including the Aaronic benediction and the Lord’s Prayer) and other  blessings for those who wish to learn a little more Hebrew. A couple of maps show Yeshua’s travels in the 1st century AD as well as a modern map of Israel. Best of all, you can acquire all of this for a very modest price: I paid about £25 for my copy but you can also get it at discounted prices from smaller retailers. See here for just one example.

I would highly recommend the TLV to avid readers of the Bible. It will come in especially handy when witnessing to Jews but can be enjoyed by anyone who appreciates the deep Hebrew roots of the Christian faith.

 

Dr Neil English shows how the Christain faith has inspired visual astronomers over the centuries in his new historical work; Chronicling the Golden Age of Astronomy.

 

Post Scriptum: You can also read the TLV(or indeed any other Bible translation) online by visiting BibleGateway.com

 

De Fideli.

In Praise of Barlow Lenses.

Three fine, low-cost shorty Barlows, ideal for use with my Newtonian reflectors. From left to right: the Meade 3x, the Orion shorty Barlow 2x and the Astroengineering 1.6x Barlow.

In this day and age, where almost every item of equipment we use under the stars is taken for granted, it pays to remember that we have a lot to thank our astronomical forebears for. A case in point is the humble Barlow lens, which has enjoyed a very long and illustrious history with visual observers, where today it remains an indispensable tool as well as a cost-saving device for the amateur astronomer.

Contrary to popular belief, the concept of the Barlow lens does not reside entirely with the musings of the English mathematician Peter Barlow (1776-1862), but actually had its origination in the fecund mind of the 18th century German philosopher and mathematician, Christian Wolff (1679-1724), who first conceived of the idea of adding a concave lens ahead of the eyepiece but behind the objective of a telescope  in order to provide greater magnification and with a slight increase in focal length. The result had mixed fortunes however, in that the resulting images in an achromatic telescope, while certainly enlarging the image, also deteriorated the achromatism achieved by the combination of the crown & flint object glass.

Charistian Wolff(1679-1724) : the originator of the Barlow lens concept in the 18th century. Image credit; Wiki Commons.

The problem was once again studied with renewed vigour in the first half of the 19th century, when Peter Barlow, then a Professor of mathematics at the Royal Military Academy, Woolwich, England, computed the design of an achromatic concave lens which was made by the optician, George Dollond, and mounted in a telescope where it showed very promising results. Some of the earliest ‘guinea pigs’ to experiment on the new device included the Reverend William Rutter Dawes and the Admiral William H. Smyth, who both commented favourably on the new contraption as early as the late 1830s and early 1840s, reporting that the image was left just as colour free as when the telescope was used without the contrivance, even allowing them to vary the magnification at will by moving the doublet lens either towards or away from the ocular lens.

The device, now commonly known as the Barlow lens, enjoyed rapid success. This author is reminded of the work of the astronomers serving in the employ of the Victorian tycoon, George Bishop, who had set up a lavishly-equipped private observatory in 1836 at South Villa, Inner Circle, Regent’s Park, London, where the Barlow lens is vividly described:

An achromatic lens( the macro-micro lens), which slides into the tube of the micrometer, was frequently used by Mr. Dawes in his observations of double stars. The effect of the interposition of this lens is to increase the magnifying power nearly in the ratio of two to one, without any very serious diminution of light. It is, therefore, of great service in the measurement of difficult objects which require increase in power with considerable light.

xii-xiii Bishop, G., Astronomical Observations Taken at the Observatory , South Villa, Inner Circle, Regent’s Park, London, During the Years 1839-1851

How does a Barlow work? Because it is a negative(diverging) lens consisting in its most basic form as either an air-spaced or cemented crown-flint doublet, it changes the angle of convergence, making it longer, as though the beam were coming from an objective lens or primary mirror with a longer focal length. What this means in effect is that a 2x Barlow will double the effective f ratio of your telescope, turning an f/5 system into an f/10. And though the Barlow lens can introduce some additional errors into the optical train, if well made, it will almost certainly remove more aberrations than it generates. This is easy to see when using an ordinary eyepiece, such as a 20mm Plossl or some such, in a fast optical system like my two Newtonian reflectors. Used without a Barlow lens, the 20mm Plossl will give very good on-axis performance but less so off-axis. Now insert a 2x Barlow lens ahead of the eyepiece and the off-axis performance is considerably improved! That’s because the cone the eyepiece ‘sees’ looks like an f/10 optical system and not an f/5 system.

In the days before anti-reflection coatings, Barlow lenses caused a small but noticeable reduction in image brightness, as well as the odd ghost image due to internal reflections, especially on bright objects, but with modern multi-coatings appplied to all air-to-glass surfaces, this light loss is reduced to negligible levels(~3 per cent).

Barlows come in all shapes and sizes, offering magnification boosts in the range of 1.6x right up to 5x. That said, by far the most commonly used Barlow lenses offer powers of either 2x or 3x. In general, longer Barlow lenses tend to give greater magnification boosts than shorter ones, but there are always exceptions.What is more, the power printed on the barrel may not be the power you get in field use, but it’s normally quite close. In addition, with refractors that employ 90-degree star diagonals, a 2x Barlow used in normal mode can also give a 3x boost if screwed into the front of the same diagonal. Bear in mind though that most modern Barlow lenses are intended for use at the power they show on the barrel and may not perform quite so well when moved to provide a different magnification. One should always avoid models offering a range of magnifications by moving the optics in a sliding tube, for example.

The Barlow lens has the inherent property of increasing the eye relief of any eyepiece used in combination with it. This is of considerable advantage to those who enjoy very short focal length Plossl and orthoscopics, for example, which by nature offer amounts of eye relief broadly similar to the focal length of the ocular used and thereby improving the degree of viewing comfort experienced by the observer.

With my fast (f/5) Newtonian telescopes, I have found through experience that shorty Barlows are better than their longer counterparts, because they always reach focus with them.That said, shorty Barlows also increase eyerelief more than longer Barlows. I have used this to great effect in my study of double stars with a 130mm f/5 and a much larger 305mm f/5 Newtonian. For example, when combined with one of my favourite eyepieces used to resolve close binary systems; a Parks Gold 7.5mm ocular, a 3x Meade shorty Barlow provides a supremely comfortable field of view at 260x in the 130mm telescope with wonderful, edge-to edge-sharpness.

Another favourite with a Barlow lens is my old 4.8mm T1 Nagler. This high power eyepiece delivers a magnification of 135x in the 130mm f/5 by itself but the eye relief is quite tight. All that changes though when I use it in conjunction with my 2x or 3x Barlow lenses (yielding powers of 270x and 405x, respectively). Eye relief is much improved and the views that little bit more enjoyable!

When Barlowing longer focal length eyepieces, care must be taken to ensure it does not strongly vignette the outer part of the eyepiece field. If the field stop of the eyepiece is greater than the clear aperture of the Barlow, then it will cut off some of the light coming from the outer sections of the eyepiece, resulting in significant light loss and a reduction in the true field presented. Look at the two Barlows shown in the image below, for example. The Barlow shown on the left is the Orion 2x shorty Barlow and the one on the right is the 3x Meade Barlow. Note the larger clear aperture of the former, which makes it better suited for magnifying low-power, long focal length oculars.

The 2x Orion Shorty Barlow(left) is better suited to boosting the power in long focal length eyepieces.

In recent years, a number of firms have brought to market so-called “apochromatic” Barlow lenses with some kind of low dispersion glass included in the prescription. These can often be sold at higher prices than regular, “achromatic” Barlow lenses with the implication that they will perform better. This is nonsense however, as a good achromatic doublet with properly applied anti-reflection coatings will give essentially the same performance. Indeed, one of the first ‘apo’ Barlows this author has experienced; the Meade # 140; performed significantly worse in field tests than a standard achromatic system costing half as much! The truth of course, is that the introduction of apochromatic Barlows is yet another clever marketing gimmick that has caught more than a few tyros off guard. As proof of concept, consider the excellent Barlow lenses long offered by well established firms such as TeleVue, who make some of the best long Barlows money can buy. You won’t have to look long to see that all of the Barlows Albert Nagler has brought to market are well-made achromatic doublets. If there were an advantage of including low dispersion glass in their prescription, don’t you think Uncle Al would have done it long ago?

Nor will a Barlow lens improve the colour correction of an achromatic refractor, as some amateurs have claimed on the vulgar forums. The dispersion caused by the achromatic doublet is completely unchanged when using a Barlow lens. Neither will it increase the depth of focus of the telescope when used normally. That said, Barlows can certainly help achieve larger fields that are corrected for the Seidel aberrations such as coma, for example, which can be mildly annoying to those who use fast f/4 and f/5 relative apertures.

Consider a case in point: the coma free field of a Newtonian system in millimetres, scales directly as the cube of focal ratio. Specifically;

The coma free field = 0.022 x f^3.

So, for my f/5 Newtonian we obtain a coma free field = 0.022 x 5^3 = 2.75mm.

Next, consider how this translates into true field.

True field in radians is given by; coma free field/ focal length.

Thus, the true coma free field in the 650mm Newtonian will be:

(2.75/650) = 0.0042 radians, and then converting to angular degrees gives 0.0042 x 360/2pi = 0.24 degrees.

Consider next a typical high−power eyepiece used in double star divination. As mentioned above, one of my favourite combinations for close double star work is a 7.5mm Parks Gold coupled to a 3x Barlow lens, with an apparent filed of view of about 50 degrees. This yields a power of 260 diameters in the 130mm f/5, so the coma free field at this enlargement is: 260 x 0.24 = 62.6 degrees!

This means that there is no coma to worry about across the entire field of view using this particular configuration. Barlows will similarly reduce the effects of other Seidel aberrations in similar fashion(though to a varying degree corresponding with how those said aberrations fall off with focal ratio). This helps keep the images of the stellar disks nice and crisp as they move from one side of the telescopic field to the other.

Barlow lenses are cost-saving devices too. Indeed, a savvy telescopist can dispense with acquiring  a complete set of half a dozen eyepieces say, and instead choose just two or three oculars and a Barlow lens(or two) to achieve the range of magnifications one desires from the telescope. For example, if you have a 25mm and 8mm Plossl, as well as a 2x Barlow used with a telescope with a focal length of 800mm, you can get a nice range of powers;  32x, 64x, 100x and 200x.This is especially true since good Barlow lenses can be had for considerably less money than a fixed focal length eyepiece. My own Barlow lenses cost between £20 and £30 and perform handsomely with virtually all eyepieces I couple them to.

For those folk who dislike the change in eye relief caused by a Barlow lens they should consider telecentric devices like those marketed by TeleVue( the Powermate) and Meade. These will not increase the eye relief you get with a given ocular and also maintain the same focus position one enjoys when the eyepiece is used alone. They are however, considerably more expensive than regular Barlows.

Barlows also have a very important role to play in astro-imaging, particualrly high-resolution lunar and planetary photography, where they provide very effective focal length boosts and thus an appropriate image scale. They are also supremely useful in binoviewing, by decreasing the amount of in-focus travel necessary to achieve focus with many of these devices.

So, in summary, Barlow lenses serve as very important tools for the modern visual observer and imager alike, and are thus very unlikely to go out of fashion any time soon. Good ones can be had fairly inexpensively and will provide the user with a lifetime of applications.

 

Neil English is author of Choosing and Using a Dobsonian Telescope.

 

 

 

De Fideli.

Sorting the Wheat from the Chaff: Small Touches that Make a Good Binocular Great.

Binoculars under test, clockwise from top left; The Barr & Stroud Savannah 8 x 42, the Barr & Stroud Sierra 10 x 50, the Pentax DCF 9 x 28, the Celestron Nature DX 8x 25 and the Opticron Aspheric LE 8x 25.

Not all binoculars are created equal. Some match the advertisement claims, while others do not. In this blog, I’ll be exploring optical and mechanical features that I like in a hard-working binocular and whether or not the price paid for a binocular matches its performance in the field.

Coatings & Baffles:

Okeydokey. Let’s get started.

The reader will note that all the binoculars (featured above) are meant to be fully multi-coated. Here is what I understand the term to mean:

All glass surfaces have multiple coatings and it is the best kind, resulting in light transmission of 90-95% for bright, sharp and contrast images.

Source here.

 

In the first investigation, I performed a bright light experiment to test for;

1. On-axis ghost images which is a sensitive test of the quality of the anti-reflection coatings applied to the optical components within the binoculars.

2. Off axis flaring which tests how good light baffling works in the instruments.

The light source needs to be small and as bright as possible. For this, I elected to use the torch on my iphone with the setting set to maximum. The ambient light was dimmed by pulling my living room curtains in such a way as to leave a small amount of daylilight to illuminate background objects. As well as looking for on-axis reflections and off-axis flare, I studied how well defined the images were immediately behind(backlit) and around the light source.

Performing a small, bright light test in the comfort of my living room. Note the small amount of daylight left in the room to assist imaging backlit objects around the light source(my iphone torch). Note the tiny reflection from the iphone camera lens itself near the centre of the picture.

All the binoculars can be sharply focused at the close distance chosen for the test(~3 metres) and all the images were performed at the position of sharpest focus.The experiment was performed using both eyes separately to check that the effects noted were in any way dependent upon the eye barrel used.

To quantify the effects I chose a number scheme from 1 through 10, with 1 representing very poor perfomance and 10 being sensibly perfect. It must be noted that no binocular, no matter how well appointed, can achieve a 10 score. Even the very best instruments display some degree of unwanted internal reflection and/or off axis flaring. Thus, to expect none at all is quite an unreasonable proposition.

Results:

Instrument                           On-axis internal reflections               Off-axis flaring

Nature DX                                               2                                                  4

Pentax DCF                                            5                                                  6

Opticron Aspheric LE                             4                                                  5

B&S Sierra                                              8                                                 8

B&S Savannah                                        8                                                 9

 

Discussion:

No significant differences between the left and right barrels were uncovered. The results documented are thus representatve for both eyes.

All the binoculars gave acceptable results with the exception of the Celestron Nature DX. The on-axis internal reflections were very strong and bright, with some reflections taking up quite a bit of the field of view. This made imaging backlit objects very difficult. If this is a fully multi-coated binocular then my name is Mickey Mouse. Off-axis flaring was also the strongest in this unit.

To my suprise, the Opticron proved less effective than I had expected with a few fairly prominent reflections on-axis but noticeably better off-axis performance. It was overall however, in a different league to the performance exhibited by the Celestron unit.

The Pentax also suprised me as I expected it to have the best performance, based solely on its reputation for quality and the not inconsiderable price I paid for the unit. It displayed one bright, unwanted reflection on-axis, but had improved off-axis performance in comparison to the Opticron unit. In addition, the definition of backlit objects was considerably improved in both the Pentax and Opticron units over the Celestron.

To my surprise and delight, both the Barr & Stroud Sierra 10 x 50 and the 8 x 42 Savannah showed much more subdued on-axis reflections than the Opticron and Pentax. Instead of bright spots, both these binoculars gave very much more subdued reflections. They were certainly present but with far lower intensity. Off-axis performance was also very impressive, with the nod going to the Savannah. Backlit definition was also excellent in both these instruments. The reader will also note that larger aperture instruments collect more light and so might be expected to have more on-axis internal reflections and off-axis flaring than the smaller aperture binoculars tested. That this was not found to be the case in both the Barr & Stroud units was quite remarkable!

Conclusions: Buyers should be wary of marketing claims.  The Celestron Nature DX clearly has inferior coatings to the other instruments tested and is certainly not fully multi-coated in the same way as all the other units were. This is in keeping with its low price(the lowest of all the instruments tested) and could be said to be an acceptable tradeoff owing to its very low street value (£59 paid). Still the result is rather worrying, as I would reasonably expect the larger DX models to be manufactured in much the same way, and so they may have undergone the same shortcuts somewhere in their construction. Any owners of larger Nature DX binoculars need to check(don’t go all proud on me!) this out and report to the amateur community.

Considering the price paid for both the Barr & Stroud units was about the same as the Pentax binocular(in fact, the Savannah, which I purchased secondhand cost me significantly less), I feel they both offer excellent protection against internal reflections and are very well baffled. Whoever made these units knew what they were doing and properly executed the technologies available to them.

So you don’t always get what you pay for.

Caveat Emptor!

A general note on on coating tests: If you’re a binocular collector, why not perform your own set of tests on them to see if they show evidence of sub-standard anti-reflection coatings? I would expect older models to fare worse in such tests e.g. vintage binoculars made in the post-war era and the like.

A general note on baffling: It occurred to me that while baffling is an important design feature in a good binocular, it is possible to over do it. A well baffled instrument produces images that are richer in contrast than an instrument with inadequate baffling, all other things being equal. But manufacturers can deliberately over baffle the light path with the aim of maximising the punch of an image, but at the expense of cutting off a little too much light and thereby restricting its effective aperture. This may go some way to explaining why some models in the same price range can display significantly different images, some over-emphasing baffling to generate the maximum contrast but where the images are a tad dimmer, and those that produce brighter images but with less aggressive baffling. Since many birders use their binoculars during daylight hours, an aggressively baffled instrument may be judged as having higher contrast, but during more critical testing during low-light conditions or viewing the night sky, its restricted aperture may become more noticeable.

The effects of recess depth in binocular objective lenses: Small design features can make meaningful differences to the quality of the images garnered by a binocular. In this section, I would like to discuss the importance of having objective lenses recessed from the front of the instrument in order to minimise the effects of stray light entering the optical train during bright, daylight operations.

What I’m effectively talking about here is what a lens shade or hood does. The function of such a device is to reduce lens flare comng from the peripheral field as illustrated below for a camera lens;

Scheme of a lens with lens flare. A lens hood is designed so that it does not block the angle of view of the lens. Lens hoods block the Sun or other light source(s) to prevent glare and lens flare. Image credit: Wiki Commons.

It also doubles up to provide some protection of the object glass during adverse weather conditions, such as occurs in rain, mist and when side winds bring air-borne dust and other materials with them.

For the sake of brevity, I will only illustrate the two extremes in the binoculars discussed here. First take a look at the very deeply recessed lenses on the Barr & Stroud Savannah. It measures 7mm!

Note the very deeply recessed objective lenses in the Barr & Stroud Savannah binocular, measured to be 7mm.

Contrast this to that found in the Celestron Nature DX binocular, which had a measured recess of just 3mm.

The very shallow recess of the Nature DX objective lenses (3mm).

For the record, the others fared as folllows;

Barr & Stroud Sierra: 5mm

Pentax DCF: 4mm

Opticron Aspheric LE: 4mm

It is the opinion of this author that having a reasonably functioning lens shade does improve image contrast in daylight images, especially when viewing under bright, sunlit conditions. I was very glad to see that the Barr & Stroud instruments were, yet again, well appointed in this regard. It’s yet another small touch that will be appreciated by an avid binocular enthusiast.

The importance of good quality eyecups: Good eyecups make for comfortable, immersive binocular viewing. If too flimsily made, they can be uncomfortable to set your eyes against, or fall out of position when twisted up. For me, there is nothing more frustrating than to have to readjust the eye cups on the fly while making observations. Cheaper models invariably come with crudely made plastic cups that quickly lose their rigidity after a few weeks of hard use. Better made eyecups usually come in the form of metal-over rubber and can be set to a variety of positions that hold there, even when a little pressure is applied to them, either by touching them with your fingers or pressing your eye up to them when conducting an observation.

Of the binoculars considered here, three are particularly worthy of a few words; the Pentax DCF, the Barr & Stroud Sierra and Savannah.

The Pentax DCF has good quality eyecups. They provide the user with a choice of four positions and so can accommodate virtually anyone, either without glasses or with them on. They also stay in place when pressure is applied to them. My only gripe is that they they do have a bit of play in them and could be a bit more rigid.

The Pentax DCF has well-made metal-over rubber eyecups that off four positions, from fully retracted to fully extended. Here they are shown in the second position, midway between the maximum and minimum positions that user can choose from.

The Barr & Stroud Sierra and Savannah have significantly different eyecups as the photo below reveals:

The Barr & Stroud Sierra(left) and Savannah(right) have different eyecups, with the latter being smaller and considerably more rigid than the former.

Both use metal-over rubber. Those found on the Sierra model are typical of what you’d find on a mid-priced binocular of this size. The eyecups click nicely into place, offering three positions for optimal eye relief. They are sufficiently well made to last indefinitely if properly cared for. That said, once again, the Savannah really surprised me! Specifically, the eye cups are far more rigid than in the Sierra and click into place with a commanding “kathud” sound. What I found remarkable is that there is very little play to to be had with them. Once clicked into place, they stay in place. You’ll never have to worry about them slipping out of position while using the instrument.

What does this buy you?

Peace of mind!

Now, I’m not saying that the quality of the eyecups on the Savannah is in the same league as those beauties made by Leica and Swarovski( I recently enjoyed the use of the 8.5 x 42 Swarovski ELs), for example, which are works of art, both mechanically and ergonomically, but I doubt anyone would be unimpresed by such high quality eyecups on the Savannah. Indeed, you simply won’t see this kind of quality on any mid-priced binocular that I know of. They are dependable, rigidly set, and a joy to use in the field.

The eyecups on premium model binoculars such as the Swarovski 8.5 x 42 ELs are a mechanical marvel.

The wonderful quality of the twist up eyecups found on the Barr & Stroud Savannah  8 x 42 binocular: they just work well, with zero play and no fuss.

 

Thoughts on Dioptre Adjustment:

A typical position for the dioptre adjuster in many entry-level and mid-priced binoculars. It is usually found under the right eyepiece and is adjusted by twisting it clockwise or anti-clockwise, as appropriate.

Most roof prism binoculars have their dioptre adjustment setting under the right ocular lens. It usually involves twisting a ring either clockwise or anti-clockwise, as appropriate, until both eyes show a perfectly sharp image. This works very well indeed, but some dioptre adjutsment rings are either too stiff or too loose, with the result that tweaking it and maintaining its precise positioning can be problematical. High-end, premium models such as those made by Leica and Swarovski cater especially well for the individual in that one can lock in the correct dioptre position by pushing the focuser forward, dialling in the correct dioptre setting, and then pushing the focusing knob back into place, thereby settin it permanently. This is ideal and a very clever mechanical solution.

The Barr & Stroud Savannah binocular uses a very different strategy however, by placing the dioptre adjustment on a dial just ahead of the focusing wheel as shown below:

The Barr & Stroud 8 x 42 Savannah has its dioptre adjustment setting immediately ahead of the focuser. It adjusts the position of the right barrel optics.

As I explained in a previous blog, I find myself tweaking the dioptre setting fairly frequently and I have elected to do this by using bright stars in the night sky rather than using a terrestrial target. The reason I do so is that I have found that bright daylight targets present an overwhelming amount of visual information to the eye and though you can usually get very close to perfect, I have found small but consistent discrepancies between the position I chose by day and where it is adjusted to at night. Focusing on a bright point source such as a star yields an easy way to remove that ambiguity. I simply look for the tiniest, brightest star images the right barrel can provide.This has become my default custom when using the instrument for star gazing.

But doing this using a dioptre adjusting ring positioned immediately under the right ocular can be a little awkward and sometimes a bit frustrating, especially if the dioptre ring is stiff. In contrast, it is very easy to move my finger forward just a little to adjust the dioptre setting on the Savannah unit, allowing very precise tweaking of the dioptre setting to be made. I think this is a very well thought-out design feature on the Savannah that is not found on many other models.

A Strong Bridge: The design of the bridge mounting the two barrels of the binocular also has an impact on how well it operates in the field. Specifically, if the hinge is too loose, you will have to readjust the IPD every time you use it; not a deal breaker in its own right, but slightly inconvenient. Much better is a binocular that holds its IPD precisely from viewing session to viewing session. The Nature DX is quite stiff, as are the Barr & Stroud instruments, but the Pentax DCF and Opticron units are a bit too loosely mounted in my opinion.

The Savannah binocular in particular, has a very strong bridge, such that I have never needed to readjust it when it is taken out of its case. And when you consider that I’ve literally done this hundreds of times since I acquired in the autumn of 2018, I’d say that’s pretty good going! No faffing about, just remove from case, remove the lens caps and you’re good to go!

The value of a good carry strap: The carrying straps that come with many binoculars( even some mid- to high-end models) are of poor general quality. They’re usually made of poor quality plastic-based materials and fray easily. Having a good quality, padded strap  is a far better option going forward, as the more comfortable the strap, the more you’ll likely use your binocular. In addition, cheap straps cut into your skin more and in hot weather can even cause heat rash and some blistering. One of the first things I’d recommend in upgrading a binocular is to invest in a more durable, high-quality strap.

The straps that come with all of the binoculars I have discussed, with the exception of the Barr & Stroud Savannah, are of generally poor quality and could well do with upgrades. This is something I hope to do remedy over the coming months. The Savannah comes with a nice, padded strap that is very comfortable to use and will not come apart in rough field use. It was a standard accessory with the binocular; complete with the Barr & Stroud logo; a nice touch for sure and something that can only be appreciated by using the instrument for prolonged lengths of time.

A quality carry strap is an important feature if comfort is held as a premium.

Recommending an all-purpose binocular to the masses: We’ve now reached the end of this blog and it’s an appropriate time to reflect on what a quality binocular should behave like. As you can gather, I am very enthusiastic about the Barr & Stroud Savannah in particular, as a full-featured instrument that includes a lot of nice touches but at a price that won’t leave you short of breath(it retails in the region of £120-140 UK). Optically excellent(with a whopping field of view of 143m@1000m or an 8.2 degree field), water proof, and built like a tank (it tips the scales at 810g) with a 10 year warranty, the company has clearly gone well beyond the call of duty to deliver a high quality instrument that will stand the test of time. Indeed, I was so enthusiastic about this particular unit that I ventured onto the vulgar forums to give my vote to it and also to sing a wee tune:

Oh I do like to be beside the seaside

Oh I do like to be beside the sea….

Oh I do like to stroll along the prom prom prom

Where the brass band plays diddleyumpumpum.lol.gif

 

I also suggested there that someone else put this binocular to the test; someone honest and experienced that doesn’t hold grudges against other people.

If that’s YOU,  then you’re in for a pleasant surprise!

 

Neil English was born at an early age and is Professor Emeritus of Tomfoolery from the University of Life.

De Fideli.

Some Comments on Pocket Binoculars.

A representative sample of pocket binoculars; clockwise from the top: the Opticron Aspeheric 8 x 25 LE, the Pentax DCF 9 x 28 and the Celestron Nature DX 8x 25.

Hello again everyone!

Binoculars come in all shapes and sizes, and at prices that suit virtually everyone’s budget. As you may be aware of, I’ve re-ignited my interest in the modern binocular market, having somewhat neglected it for the best part of three decades. But I’ve been making rapid progress and would now like to discuss the market for the smallest binoculars; the so-called pocket variety.

Though any objective look at this market is very much like hitting a moving target, I acquired three products which I believe are fairly representative of the entry-level to upper-mid to premium class of pocket binocular that can be purchased. First off, let’s come up with a working definition of a pocket binocular. To my mind, these would be instruments under 30mm in aperture and have magnifications in the range from about 6x  to 10x. As their name suggests, they are small enough and light enough to fit inside a regular pocket (though some pockets are certainly larger than others lol!)  and so would be no larger than about 4 square inches in area and weigh less than about 400g.

Unlike all the other classes of binocular; including compacts, full-size and large instruments; the reader may be surprised to learn that even the most expensive models in the pocket class of binocular are not exorbitantly priced. Indeed, you can acquire models from the threee premium binocular manufacturers(Zeiss, Swarovski and Leica) for about £500 or sometimes less. This reflects their limited utility; very useful for hiking and other outdoor excursions that require strict minimisation of weight but ultimately not an instrument one would happily use where there is easy access to a larger(say mid-size) instrument. That said, you can get essentially the same performance out of some models that cost significantly less than the premium brands, if you know what to shop for. That just reflects how manufacturing technology has caught on.

Now, I do a fair amount of hill walking and have learned the hard way that even my favourite binocular – the magnificent Barr & Stroud Savannah 8 x 42 wide angle – is a bit of a pig (weight wise) to climb with. That stoked my interest in acquiring a smaller unit dedicated to enjoying quick looks around the landscape from an elevated vantage and this naturally led me to testing three roof prism-based units units that can be acquired relatively inexpensively; either newly purchased or acquired second hand; the Celestron Nature DX 8 x 25mm (purchased new for £59 plus shipping), the Opticron Aspheric 8 x 25mm LE (actually my wife’s binocular, purchased new for £110 a few years back with the slightly modified new version retailing now for £129) and a Pentax DCF 9 x 28mm (purchased second hand for £119 but still under warranty and now available for £199 in the newer (AD) incarnation).

Yours truly recently surveying the landscape with a pocket binocular atop the Meikle Bin, Campsie Fells, Scotland, elevation 1,870 feet. Check out the gibbous Moon at upper right!

These were not acquired for specific astronomical use, though I did find out that there are significant differences between them when looking at some astronomical targets. But you’ll need to read the rest of this blog to find out those details!

Nota bene: A new discussion has arose on tiny binos here lol.

Let’s take a closer look at the instruments. First up, the Celestron Nature DX 8 x 25. Full specifications here.

The Celestron Nature DX 8 x 25 has twist-up eyecups giving very comfortable eye relief.

This very cost-effective pocket binocular from Celestron offers many attractive features for the savvy consumer. Weighing 343g, the package includes the binocular, a basic neck strap, a lens cloth, nicely fitting rubberised ocular and objective lens covers and a decent carry case. It also includes a basic instruction manual to get you going fast. What is rather remarkable is that the binocular has a few optical features that were offered only on premium models just a decade ago; including fully multi-coated optics, BAK-4 prisms, with phase correction. It is also waterproof and is purged with dry nitrogen gas preventing internal fogging and minimising internal corrosion. The Celestron Nature DX 8 x 25 offers a very generous field of view of 7.2 angular degrees which is actually quite remarkable for such a low cost unit.

Looking down on the Celestron Nature DX 8 x 25. Note the specifications on the large, central focusing wheel.

The plastic eyecups twist upwards giving a comfortable 14mm of eye relief. The cups are kept down for eye glass wearers. The dioptre setting is reassuringly stiff and is located just under the right eyecup. Viewing through the binocular is very comfortable and the large field of view is bright and sharp across most of the field. Only in the outer ten per cent of the field can one detect a little softening of the image. Chromatic correction is very good, as is the control of pincushion distortion.

The objective lenses on the small objectives of the Nature DX binocular have good coatings.

It has a stiff, central hinge that can accommodate virtually all IPDs. It has quite a solid feel in use. The body is made of a low mass but strong polycarbonate material with a plastic- like(read non rubberised) green overcoat. Grip is adequate but I would have liked to have a higher friction, rubberised over coat.

The large, centrally placed focusing wheel is quite stiff and only turns through ~ 290 degrees, so less than 1 revolution between infinity and closest focus(an impressive 2m). This result is at odds with the claims of some other reviews I have read on the Nature DX (720 degrees, or two full revolutions claimed!). See here for an example. Perhaps it is unique to this small Nature DX model?

The instrument gives remarkable depth of focus! When the wheel is turned to the end of its travel so that objects in the far distance are focused, my eyes were able to get very sharply focused images all the way down to about 35 yards distance!

I did discover a significant flaw in this instrument however; point it at a bright light source at night or at the Moon, and it will show strong internal reflections/lens flaring. I found observing the Moon to be particularly annoying with this binocular and if imaging a backlit scene during the day, it will also throw up the same reflections which reduces the punch of the image. You cannot see these reflections when looking at most scenes though; it shows none on even the brightest stars, as verified by my testing on the Dog Star, Sirius. I do not know whether these internal reflections are found on other Nature DX models but it can (and should) easily be tested. But for £59 plus shipping, I can’t really complain. Afterall, some internal reflections are found in all binoculars, even premium models.

The Celestron Nature DX pocket binocular comes with a decent soft-padded case, a lens cloth and a basic neck strap. The ocular and objective lenses also have good rubber caps.

The user will have to decide if this flaw is annoying enough to justify passing on the purchase of this product. Everyone’s different I suppose! This might bother some observers more than others; the instrument is otherwise quite excellent and I can see how it has been lauded(Cornell Ornithology Lab) as a great entry-level birding binocular. That said, all of the reviews I have read never mentioned this flaring/internal reflection, which is somewhat alarming. It just seems to have gone unnoticed. I think simple tests like this should be mandatory for all optical testers.

The model has recently been discontinued from the Nature DX line.

Next up, the Opticron Aspheric 8 x 25 LE

The little 8 x 25 Opticron Aspheric LE pocket binocular.

The Opticron Aspheric LE 8 x 25 is a well-designed pocket binocular. Tipping the scales at just 291g, this is the lightest binocular of the three by a significant margin. It has a very well constructed double-hinge design that also allows the barrels to be folded right up to each other, also making it the most compact of the three models discussed here. The hinges fold outwards to accommodate virtually any IPD and can be comfortably set in seconds.

The Opticron Aspheric LE 8 x 25 has an elegant double-hinge design that enables it to be folded up( it’s just 66mm wide) for very snug transport anwhere, anytime.

Unlike the Nature DX, it is not weatherproof or nitrogen purged; but not a big deal as my wife likes to remind me. As you can discern from the first photo of the unit above, the optics are of high quality with a full multicoating, which includes a phase correction coating on the roof prisms, that delivers bright, high-constrast images of objects during well-illuminated, daylight conditions.

The eyecups twist up for non-eyeglass wearers and offers generous eye releif (16mm). The eye cups are of a higher standard than those found on the Celestron Nature DX and appear to be rubber-over-metal. They stay in place reasonably well.

The rubber-over-metal twist up cups are of a higher standard of workmanship compared to the Nature DX binocular and offer 16mm of eye relief. Note the small, central focusing wheel that is quite hard to grip.

Optically, this is a sharp shooter, offering well-correcetd images over a 5.2 degree field. I felt that this was rather a small field though, in comparison with that offered by the Nature DX binocular discussed previously and does take a bit of getting used to if one is especially fond of wider views. But its aspherical optics certainly deliver the readies, producing a lovely, flat, low-disortion images from edge to edge. I guess this is the price one has to pay for a more restricted field of view.

Internal reflections are much better controlled in this unit than in the Nature DX, as evidenced by pointing the instrument at the bright Moon at night or other bright sources of artificial light. Backlit scenes during the day are a tad more contrasted too. Besides the small field, the only other issues I had with the Opticron pertain to its very small focusing wheel, which is hard to grip in my (not overly large) man-sized hands, and it’s a nightmare to use with gloves.  It can often prove difficult to turn the focuser fast enough to keep up with moving terrestrial targets such as rapidly moving corbies. I believe the updated WP model(with the same specifications so far as I can see) has a slightly larger focusing wheel with better grip.

In addition, I found its very light weight a bit offputting, as it was difficult to find a good, secure position in my hands. The unit comes with its built-in lilac coloured lanyard, so no need to affix a separate strap. I’m not really a fan though, as it feels as though you are being slowly garrotted when walking with the binocular around your neck lol!

The tiny but well made carrying pouch for the Opticron Aspheric LE 8 x 25 pocket binocular.

All that being said, my wife loves it; lanyard and all! She says it looks as good as operates, with small, elegant black tubes that easily fold up in tiny pockets. It’s also perfect for her quick looks at the bird table in our garden and for taking on her hill walks with her girlfriends. I don’t use it very often though, as her dioptre setting is much different to my own!

Finally, let’s take a good look at the Pentax DCF 9 x 28mm LV pocket binocular.

A liitle gem: the remarkable Pentax DCF 9 x 28mm LV pocket binocular.

 

Some information about the unit when the product was first launced back in 2009.

And here’s an independent review of the same instrument.

The reader will note something rather interesting from the review article linked to above; all of the compact binoculars highlighted in the table the reviewer presents, including premium models, like the Leica Trinovid 10 x 25, do not use ED glass. This is an important point, as it serves to highlight the fact that no real gains in performance are achieved by inserting one or more ED elements in the objectives of these binoculars. If there was an obvous advantage, don’t you think companies like Leica would have insisted on using it? Though it is conceded that some pocket models like the Zeiss Terra ED 8 x 25 do have ED elements, their cost is actually consideraby less than the Leica Trinovid(as of early 2019 average UK pricing). I view the use of ED glass in such small binoculars as a clever marketing ploy.

Now back to the Pentax DCF binocular.

The instrument tips the scale at 365g; definitely on the heavy side as pocket binoculars come, but still under the 400g cut-off point between pocket and compact models.

The instrument is weather proof and is dry nitrogen purged to prevent internal fogging of the elements. The optics are fully multi-coated and the prisms have been phase coated to improve brightness and contrast in the images. The instrument has a field of view of 5.6 degrees, noticeably larger than the Opticron Aspheric but not nearly as large as that yielded by the Nature DX. Then again, the Pentax provides a power of 9x and not 8x as the other models do, which invariably has an impact on the maximum true field achieved.

Looking from the ocular end of the Pentax DCF 9 x 28.

The instrument is very well endowed from a mechanical point of view, with a large centrally placed focusing wheel with excellent grip, even while using gloves. The wheel rotates through about 300 degrees, so not very much in the way of travel  from infinity to minimum close focus. The barrels are covered with a tough rubber coat making it especially suitable for rough field use.

I really like the metal-over rubber eyecups, which are strong and comfortable. The user has a choice of 4 positions, from fully down use with eye glasses to fully extended. I found having the eyecups twisted up to the mid-position provides all the eye relief I require without glasses. When clicked into place at a given position, the eyecups maintain their positioning even after applying unreasonable pressure.

The high quality twist up rubber over metal eyecups click into four positions and hold those positions well in field use. Note the dioptre ring under the right eyecup.

The underside of the binocular has thumb indentations to assist holding the binocular steady in field use.

The underside of the binocular has thumb indentations to assist with holding the binocular stably.

The anti-reflection coatings on the Pentax DCF are very well applied and I would rate them superior to those on the Opticron Aspheric model previously discussed. The Pentax is not nearly as compact as the Opticron however, as seen in the photo below. This was not found to be a problem; it’s still small enough to fit into a coat pocket or the palm of my hand.

The central bridge connecting the barrels do not allow the Pentax DCF to fold into the same compact size of the Opticron Aspheric binocular.Note the coatings on the Pentax( left) are a little bit less reflective than the Opticron( right).

The central hinge of the Pentax DCF is reasonably stiff but not quite as stiff as that of the Nature DX model. I find that the latter is just right for quick deployment with the correct IPD(for my eyes) achieved in seconds from its fully folded in position.

The objectives of the Pentax DCF LV are noticeably larger than the 25mm models, which has an immediate impact on its light gathering performance. Afterall, it gathers about 25 per cent more light than the other models discussed in this blog. I like the recessed position of the objectives with a little overhang from the barrels. This helps to reduce lens flaring and /or the control of stray, off-axis light while using it in the field.

The Pentax DCF objectives have excellent coatings applied to them and are nicely recsessed from the top of the barrel to help suppress stray, off-axis light.

The Pentax DCF LV 9 x 28 feels very comfortable while in use and has more of the attitude of a 30mm compact binocular than the smaller 25mm instruments tested previously. The 9x magnification is immediately apparent compared to using a 8x unit.The human eye will easily register a 12 per cent increase in magnification with just a little experience. Images appear equally bright in the Pentax in comparison to the Opticron (afterall they have the same exit pupil of 3.1) but the greater field of view is readily appreciated. Images are very sharp and contrasty with only very slight softening at the edge of the field. Control of stray light is very good; almost as good in fact as my larger Barr & Stroud roof prism binoculars( yep, you really have to experience them to know of course!). This is immediately apparent when turning the instrument on a bright Moon which shows that glare and internal reflections are very well controlled. The large focusing wheel is a bonus, moving smoothly and precisely but with a little bit more tension than I would have liked. Still, it’s perfectly fine for the tasks I intend to use it for.

I measured the close focus to be just under 10 feet. I find the 9x very useful in daytime use as it brings objects that little bit closer, aiding in the identification of small birds or subtle landmarks in the distance. I’m glad I didn’t go for something with a 10x magnification though, as this would probably have generated images a tad too dim for my liking, but your mileage may vary! It will serve me well for occasional hill walking ventures and at sports events, where its small size won’t cause me to look too out of place.

If money is an objection or if you’re frugal like me, I’d recommend purchasing quality instruments second hand. A few thoughtfully chosen questions and the answers they generate from the seller never go amiss. If you do your research and know what to look for in a binocular, you can secure real bargains for relatively small financial outlays.

Ultimately though, I would not recommend spending huge amounts on these small instruments. I find them, well, a bit unexciting. They’re just too small to use for prolonged astronomical appllications and their daytime performance, while good in bright light conditions, is noticeably inferior to mid-sized instruments under dull or low light situations, such as at dawn or dusk. In comparison, my 8 x 42 is, by far, my most used binocular; providing a great balance between portability and utility by day or by night. Sure, it’s nice to have a quality pocket binocular around, but unless I were to embark on a trek through the Himalayas, I can’t see myself reaching for one all that often.

Thanks for reading!

 

Dr. Neil English’s latest historical work, Chronicling the Golden Age of Astronomy, takes a detailed look at the life and works of great telescopists from the early 17th century right up until the modern era.

 

 

 

 

De Fideli.

For the Record: My Telescope & Binocular Collection.

Duodecim:

Duodecim: 12″ f/5 Newtonian.

12″ f/5 Revelation Dobsonian with ultra-high reflectivity coatings on original mirrors, 23 per cent central obstruction. Used regularly.

 

Octavius:

Octavius; optimus.

8″ f/6 Skywtacher Dobsonian wth ultra-high reflectivity coatings on both mirrors. Original Skywacher primary mirror, original secondary replaced by a 44mm semi-major diameter unit from Orion Optics, UK. 22 per cent central obstruction. Now retired to garden.

 

Plotina:

Plotina: 130mm f/5 Newtonian reflector.

130mm f/5 Newtonian reflector, with ultra-high reflectivity coatings, secondary mirror replaced by a slightly smaller (26.9 per cent central obstruction) by Orion Optics UK. Most frequently used grab ‘n’ go telescope.

 

Tiberius:

Tiberius: 5″ f/12 neoclassical achromat refractor.

5″ f/12 IStar sourced neo-classical refractor with R 30 objective. Subject of much former work. Now retired to garden.

 

Gaius:

Gaius, my 80mm f/5 short tube achromat.

80mm f/5 ShortTube achromatic refractor. Skywatcher objective in Opticstar tube assembly. This is the subject telescope of a new book dedicated to the ShortTube 80.

 

The Traveler:

The AstroPhysics Traveler; 80mm f/11 doublet achromat.

80mm f/11 Astrophysics labelled achromatic refractor. Orginally donated to local school but returned to me after it was found in a sad state of neglected use. School instrument replaced by a smaller, shockproof instrument. Now seeking a new home.

 

Achromatic Binoculars:

9 x 28mm roof prism Pentax DCF LV pocket binocular (2009 vintage).

The Pentax DCF 9 x 28mm LV pocket binocular.

 

8 x 42mm Barr & Stroud Savannah roof prism  super wide angle. Most used, general purpose binocular.

The Barr & Stroud 8 x 42 wide-angle binocular

 

10 x 50mm Barr & Stroud Sierra roof prism. General purpose, astronomy binocular.

The Barr & Stroud 10 x 50 roof prism binocular.

 

Pentax PCF 20 x 60 WP II: Large porro prism instrument, used on a monopod for specialised deep sky observing/solar viewing.

Pentax 20 x 60 PCF WP II porro prism binocular.

 

Future plans: converting my two Newtonian telescopes in active use to binoviewing mode. Currently investigating options.

 

De Fideli.

Product Review: The Pentax PCF WP II 20 x 60 Binocular.

Grandes Binoculares.

The achromatic telescope has enjoyed a long and illustrious career in the hands of skilled observers. In my most recent book, Chronicling the Golden Age of Astronomy, I have documented and shared with you the amazing achievements of the classical refractor over three centuries of time. But it would be quite inaccurate to claim that it has been really superceded by anything else in the modern age. This is especially true in the case of binocular manufacture, where sales of achromatic instruments vastly outsell models which possess modern ED glass. And there’s a good reason for this: ED is an expedient luxury that impacts little to the binocular view, what with their low magnifications and wide fields. For every ED model offered, there are a great deal more made with traditional crown & flint, and that is true even for some premium brands.

Consumers vote with their wallets.

We still live in the achromatic age.

Having enjoyed and appreciated the achromatic refractor for decades, I have come to the conclusion that it is in the binocular that achromatic optics has reached its zenith. Properly made, achromatic optics provide wonderful, sharp and contrasty images of the eartly and heavenly creation. This conclusion has been reached by extensive field experience of a variety of achromatic binoculars that show vanishingly small amounts of secondary spectrum and which are far more alike than different to models with ED glass, but at a fraction of their cost. These sentiments are also reflected in the models still being marketed by some big names in the large binocular world, including Celestron and Oberwerk. What these manufacturers offer is great performance at prices that won’t leave you out in the cold.

For certain kinds of visual astronomy, large binoculars simply can’t be beaten. The ability to use two eyes rather than one greatly influences the quality of the views, where it impacts depth of field perception, faint object detection and significant improvements in perceived contrast. Without a shadow of doubt, large binoculars are the single most powerful way to enjoy larger deep sky objects, where telescopes simply cannot offer the same ‘zoomed out views.’ That said, it’s very much a Goldilocks scenario; increase the magnification too much and you lose those gorgeous panoramic sights, but when the power is too low, finer and fainter details remain elusive. It was with this realisation that I took a punt on a curious large achromatic binocular made by Pentax; enter the PCF WP II 20 x 60.

That Pentax were prepared to put their name on the PCF WP II 20 x 60 is a lesson in objectivity. Why would such a prestigious manufacturer of high-end cameras and sports optics decide on a well-appointed, large achromatic binocular? The answer is that when well made, even a 20x model would deliver up wonderful, tack sharp views of the landscape by day and breathtaking celestial vistas by night. And this has been achieved at a price point that suits the budgets of discriminating amateur astronomers who just appreciate well designed classical optics; true observers rather than casual sightseers; folk who want real substance rather than the latest ‘gee whiz’ gimmicks.

                                                     A Full Featured Binocular

Though the instrument can be acquired at a good, price new (£219 UK for the latest SP model), I was lucky enough to acquire this binocular in excellent, used condition for a little over half the retail price. The former owner had taken very good care of it, added a sturdy carrying strap and dispensed with the flimsy carrying case, replacing it with a sturdy foam-lined aluminium case.

The Pentax 20 x 60 snug in its foam-lined aluminium case. Note the tripod adapter attached to the instrument.

The porro prism binocular weighs just 1.4 kilos (~3 pounds), surprisingly light for an instrument of these specifications and is water and splash proof. This may account for the WP(water proof?) in their name. The interior is purged with dry nitrogen gas to prevent internal fogging and to minimise corrosion.The body, which is constructed of a lightweight magnesium alloy, is covered with a protective rubberised substrate that is easy to grip and is tough and durable in all weathers.

The petax 10 x 60 is deisgned for rough weather use.

The optics are fully multi-coated to maximise light transmission to the eye and reducing contrast-robbing internal reflections to a minimum.

The beautifully applied multicoatings on the large 60mm objective lenses.

Hard coatings on the ocular lenses maximise their durability.

The centre focusing wheel is remarkable in two respects. Firstly, it is quite tight in comparison to other binoculars I’ve used. This was intentionally done by the manufacturer, as you’re not likely to use this instrument watching fast moving birds or some such, necessitating the rapid change of focus position. This increased tension does however allow for very precise focusing to be achieved. Secondly, there is a facility on the focuser to lock it in place. Simply push the focusing wheel forward and it is locked in; a nice design feature that can be advantageous. For example, if you end a session with the binocular focused on the stars at infinity, locking the focuser in place ensures that you can re-engage with the sky whenever you’re next out, with minimal (if any) re-focusing necessary.

The well designed focuser ensures very accurate focusing of the instrument and can be locked in place simply by pushing the focussing wheel forward, as indicated.

The strong bridge connecting both barrels of the binocular is reassuringly stiff, allowing one to easily obtain the correct inter-pupillary distance (IPD) and only requires occasional adjustment in field use.The dioptre setting is found under the right-hand eyecup allowing independent focusing of both barrels. It has just the right amount of tension and stays in place without any fuss.

The dioptre setting on the binocular lies directly under the right eye cup.

I really like the twist up eyecups on the Pentax PCF WP II 20 x 60. Like my smaller roof prism binoculars, they click into place and are quite secure. Eye glass wearers just need to hold the eyecups down, while those who don’t (yours truly included) can extend them upwards for very comfortable, full-field viewing. The texture of the cup is hard rubber which is a far cry from the cheap fold up/down eyecups seen on many other large binoculars in this price range. Indeed it is my experience that the latter can fragment in prolonged field use, necessitating their replacement from time to time. These sit very comfortably against the eyes and never need to be adjusted. Eye relief is exceptional; a very comfortable 21mm.

High quality hard rubber eye cups twist up and lock in place for non eye glass wearers. Those who wear eye glasses will likely keep them fully down while in use.

                                                    Mounting Options

It is not the weight per se that forces one to mount this binocular. As stated above, they are quite light for their optical specification. Rather, it is the 20x magnification that limits their hand-held use. That said, I can hold them reasonably steady by extending my hands a little further forward on the barrels than with my smaller binoculars and this strategy can work quite well for short, ‘quick peek’ sessions. Incidentally, I discovered thumb indentations on the belly of the instrument presumably designed to assist hand holding! Golly gosh!

Ain’t that sweet: indentations to fit the hand on these big binos!

Still, whatever jitter you have, it will be magnified 20 times while looking through it. Such high powered binos definitely require some kind of stablising action and, in this capacity, one can either elect to use them tripod-mounted or by using a monopod.

The Pentax PCF WP II 20 x 60 binocular can be easily mated to a light weight tripod with an appropriate adapter.

A word of caution; avoid using those cheap plastic tripod adapters that often attend bargain basement large binos such as the ubiquitous 15 x 70. These introduce an annoying level of flexure that will almost certainly detract from enjoying the instrument in the field. It is strongly advisable to invest that little bit more in a good quality, all-metal unit sold by Opticron and other companies. Indeed, I found the same adapter that fits my 10 x 50 roof prism  binocular also work swimmingly well with this larger instrument.

Tripods have their pros and cons though. Although they offer the maximum level of stability and have built in slow-motion controls on both axes, they are quite uncomfortable to use when aimed high in the sky. I found it quite hard to find a suitably comfortable positioning of my eyes when used in the seated position. That said, a trpod was useful in checking collimation of the barrels and certain daylight activities, but in the end the most suitable way I’ve found to use this instrument is by mounting it on a simple monopod.

Using a high quality(solid aluminium) ball & socket adapter, mounting the 20 x 60 on a monopod is quick and easy to execute.

Travelling light; the author’s preferred mode of mounting the Pentax 20 x 6o binocular using a light but strong extendable monopod and ball and socket head.

Simplicity itself; the 20 x 60 mounted on a lightweight but sturdy monopod.

Using the monopod, I have been able to get very stable views during daylight and extended periods of night use. For quick looks, I usually stand and adjust the angle of either the monopod itself or the ball & socket head. For the most stable viewing sessions however, I relax in a recliner and, securing the monopod base between my feet, have attained nearly jitter-free viewing. I have learned to place some of the weight of the binocular on my face, which increases the overall stability to a significant degree.

Yours truly suitably attired, demonstrating the use of the monopod.

 

Pentax PCF WP II 20 x 60 Optics

As the size of binoculars increase, it makes a lot of sense to decide on a porro prism design, rather than its roof prism counterpart. Porros are less expensive and just easier to make well and also offer slightly more light throughput than their roof prism counterparts. The optics of the Pentax PCF WP II 20 x 60 are notable. All lenses are fully multi-coated with a protective overcoat. The Bak-4 prisms are also multi-coated. The oculars are constructed from aspherical lenses which offer several advantages over conventional lens systems, espcially in the suppression of spherical aberration and a number of off-axis aberrations that plague conventional porro binos. In addition, fewer elements are needed with ashperical designs, significantly reducing weight.  Rather than rambling on with this, it’s best to hear it from an established optics firm. Here is a link to more information on aspherical lenses.

Collimation test

Collimation of binoculars is important especially on these high power units. One quick way to test for collimation is to mount the binocular on a tripod and select a target at least a kilometre away. I elected to use the snow capped Fintry Hills a couple of miles distant.  With the correct IPD selected for my eyes, I look through the binocular and slowly pull my eyes away until the exit pupils start to become separated and I can only see the top of the field. If there is miscollimation, one image will be raised slightly higher than the other. To my relief both images remained perfectly level. Testing for sideways collimation involves aiming at a distant target and testing to see if images at the edge of the field are precisely aligned on both sides. In doing this, I detected a very slight misplacement but it was so small that I wasn’t worried. The images merge very easily and you don’t encounter eye strain even after prolonged use.

Misaligned prisms can also be revealed by examining the shape and size of the exit pupil when the binocular is pointed at a source of light. As you can see below, both exit pupils are round and of the same size indicating that all was well.

Two round exit pupils of the same size indicate good alignment of the prisms with no picking off evident.

Daytime tests:

The binocular has a 3mm exit pupil. This ensures the best part of your eye is imaging the field. And oh what a field! When precisely focused images of daytime targets are bright and tack sharp across nearly the entre field (read 95%), indicating that that aspherical optics were working well. Contrast is excellent with very effective baffling of stray light. On axis, very little chromatic aberration could be detected but I could see that off axis some lateral colour was evident. That said, it was very slight and totally acceptable to my eye. In comparison to a side by side test made with my ShortTube 80 f/5 achromatic telescope charged with a power of 16x (5mm exit pupil) in a wider 3.75 degree field showed much higher levels of lateral colour.

Spying on a corbie perched on a TV aerial against a bright sky background about 40 yards in the distance showed very slight secondary spectrum around the crow’s jet black plumage. I deemed the result quite excellent and non-intrusive for an achromatic binocular of these specifications.

Close focus was estimated to be about 8.5 metres.

 

A Curious Aside: More on ED glass in binoculars here  and here. 

Nightime tets:

For nightime testing, I mounted the 20 x 60 on a simple monopod, as described previously. This is a very quick and effective way to get going with this large binocular. Some users of the instrument complained about the small field of view offered by the Pentax PCF, what with its 2.2 degree true field. Others commented on the sensitivity of the instrument to eye placement, but truth be told, I found neither of these things to be in the least bit distracting. You see, I’m used to very small fields working with close double stars at very high magnifications and with fields that are far smaller than what is offered by this big gun. Right off the bat, I was enjoying very comfortable, stable images. A 2.2 degree field is small as 60mm binoculars go, but it is plenty good enough to frame larger deep sky objects. To my mind, it simply boils down to training.

My first light target was the Pleiades cluster in Taurus. Getting myself comfortably positioned on my recliner and adjusting the monopod, I was absolutely blown away by the sight of this magnificent open cluster in the 20 x 60! More like an astrophoto more than anything else, the entire cluster was beautifully framed, crammed full of gorgeous blue-white starlight and razor sharp from edge to edge. The sky hinterland was jet black with none of the flaring of stellar images that I had experienced in my brief rendevous with budget 15 x 70 models.  It is immediately apparent that the field is very flat from edge to edge, with no distortions that I could register. It just exuded quality! And although I own a number of good telescopes that can collect far more light than this 20 x 60 instrument, they could not beat it in terms of delivering such a magisterial image. Focusing the binocular was particularly satisfying; very small motions can make the difference between seeing the faintest stars and not seeing them at all.

Turning next to the Sword Handle in Orion, which is also perfectly framed in the 2.2 degree field,  I was deeply impressed at the wonderful contrast and colour rendering of the bright O/B stars in the field; tiny little pinpoints of light bathing my retinas. I could easily make out the greenish hue of the great Nebula in Orion (M42) and a steady hand revealed at least two of the tiny quartet of stars comprising the famous Trapezium (Theta Orionis complex).

Though the field of view is not large enough to frame the three bright Orion belt stars, the 20 x 60 pulls out many more faint stars in Collinder 70 that are quite beyond the reach of my regular astro binocular; my trusty 10 x 50. Suddenly, this preterrnaturally lovely open cluster has become a whole lot more crowded!

In the wee small hours of freezing January nights, I would watch the sky, waiting for the Beehive Cluster (M44) in Cancer to approach the meridian. Having experienced the Pleiades, I was very much looking forward to seeing this large and sprawling open cluster in the 20 x 60. And again, it did not disappoint; the view was enthralling! The entire field was filled with pinpoint stars against a jet black sky. Using two eyes greatly enhances the view and there is a lot to be said for seeing these wonders of God’s creation in their correct orientation, as if they were made for such instruments.

The glories of the Double Cluster in Perseus were a joy to behold in this high power binocular; great mounds of starlight of varying hues with curious fans and spirals of distant suns meandering their way from their crowded centres. Compared with a 10 x 50, the view was simply in a different league!

I didn’t notice much in the way of chromatic aberration in the images, save for a brief spell with the Dog Star, Sirius. It’s brilliant light is dazzling in the 20 x 60, corruscating with various colours from moment to moment. In my opinion, secondary spectrum is a complete non-issue with this instrument for astronomical use; just set it up and go stargazing!

Although smaller deep sky objects are best examined in telescopes with more light gathering power and their ability to take higher magnifications, I nonetheless enjoyed some very pleasing views of the Auriga trio of Messier open clusters; M36, M38 and especially the sumptuously rich M37, which appears satisfyingly large, well defined and glistening with the light of many faint suns. M35 was also big and prominent in this large binocular with dozens of its constituent stars being easily made out.

This is a wonderful instrument for framing and observing the Engagement Ring: a circular arrangement of faint stars encrusted with the creamy bright Polaris as the principal gemstone. Smaller, more conventional binoculars really don’t show this structure half as well, owing to their lower power, wider fields and reduced light grasp.

With such a large and powerful binocular, the colours of stars really stand out; marmalade orange Propus, sanguine red Mu Cephei, the soft yellow pastels of Capella and the Orion belt stars, white as the driven snow. This instrument would also make a dedicated variable star observer very happy, what with its impressive light gathering power (reaching down to perhaps + 11 magnitude from a dark site with good transparency) in a very well corrected, wide field. The 20 x 60 might not be the first instrument that comes to mind for a budding comet hunter, but I am reminded of the advice of the great 19th century observer, William F. Denning, who recommended an instrument with a field of view of between 1 and 1.5 degrees for such work. And in more modern times, the distinguished comet discoverer, David H. Levy, advises that the comet-seeking instrument deliver a field of just 0.75 angular degrees! Seen in this light, the suggestion doesn’t seem quite so far fetched.

The telescope provides wonderful views of some prominent binocular doubles; Mizar & Alcor, o1 Cygni, Albireo, Mintaka and Cor Caroli, to name but a few.

Structure within Structures

The Pentax PCF 20 x 60 is a formidable instrument for delineating structures within larger asterisms. Just have a look at the stars around fiery red Aldebaran with this bazuka! Sure, you can’t see the entire Hyades but with its pinpoint stars, wonderful contrast and generous ‘space penetrating power’, as Sir William Herschel of old liked to say,  it allows you to capture painfully beautiful starfields, rich in light and colour against a velvet black sky.  It’s even more amazing when pointed at Alpha Persei; the field is littered with lovely stellar jewels sparkling through the cold dark of interstellar space. This will be a great instrument to begin a study of stellar hinterlands around the brightest stars in general, something I thought about in the past but never pursued because of other diversions. I think it’s tailor made for such projects!

Ready to go when you are: the Pentax PCF 20 x 60 can be used at a moment’s notice between heavy showers when some clear spells manifest.

Starting in Gemini and running the binocular haphazardly across the sky through Auriga, northern Orion, Taurus, Perseus and ending in the gloriously rich Cassiopeia, the binocular shows me many new asterisms which I had not witnessed before, a consequence of its unique field of view, magnification and image orientation. Almost every field stumbled upon brings new bounties, delicate arrangements of stars unnoticed in smaller binoculars; vast shoals of starlight in the open ocean of space.

Moon Watching:

In the early days of February 2019, I got several opportunities to observe the waxing crescent Moon through the monopod-mounted Pentax PCF 20 x 60 binocular. The views were amazing; razor sharp, beautiful contrast, most excellent suppression of internal reflections that can easily plague lesser binoculars. Indeed, I’ve devised this simple but highly discriminating test as a way to quickly establish whether a binocular is fit for general astronomy use. If the unit shows flare and/or internal reflections when pointed at the Moon, it’s leaking light.

The image scale of the Moon seemed larger than I expected it to be in going from a standard 10x binocular to this 20x unit. It just seemed like I was getting a higher power than the 20x marked on the Pentax binocular tube. This is no doubt an illusion, a consequence I suppose of the Moon’s taking up a larger fraction of the area of the field than seen in my trusty 10 x 50 binocular.

The earthshine from the dark side of the Moon was very prominent and as the crescent continued to grow, the binocular revealed more and more details of the lunar regolith. The image scale is great for seeing high resolution details of the battered southern Highlands. On the evening of February 10, I enjoyed a wonderful view of the three large craters; Theophilus, Cyrillus and Catharina on the eastern shore of Mare Nectaris. Up north, Atlas and Hercules could be clearly made out with a steady hand. The limb displayed a sliver of colour; sometimes green, sometimes yellow, depending on where my eyes were postioned.I judged the chromatic aberration on this tough target to be minimal and completely non-intrusive to a seasoned telescopic observer. Contrast between the bright lava fields and darker maria was very well presented, producing an extremely immersive, aesthetically pleasing view.  This will be a great binocular to observe the early waxing Moon during March and April, when earthshine is at its most prominent and I look forward to fielding the instrument for this purpose. Sure, the binocular cannot substitute for the telescope proper, but it certainly complements those high-power, high-resolution views. The big binocular has a charm all of its own and should really be enjoyed on its own terms.

Concluding Remarks:

A quality, large binocular at a great price!

As you can probably discern from the above write up, I took to this instrument like a proverbial duck to water!

The Pentax PCF 20 x 60 WP II  is an impressive performing, large binocular, with a rugged but durable housing. It is water and splash proof, making it suitable for routine and/or prolonged work by day or by night. Its high magnification requires a stable mounting system to get the best out of the instrument.The ability to lock the focus in place is a useful mechanical feature that will be greatly appreciated by all those who use it in the field.

The Pentax 20 x 60 has very high quality optics, including properly collimated porro prisms and quality multi-layer coatings that efficiently transmit light to the eye. All lenses are also fully multicoated. The aspherical optics deliver a very highly corrected field, from edge to edge. Chromatic aberration is very well controlled and is not intrusive in normal use. Contrast-robbing internal reflections are also very well suppressed in this instrument. The binocular is very easy to use and has comfortable eye relief(21mm with the twist-up eyecups), allowing hassle-free viewing for both non eye-glass wearers and those that like to observe with their glasses on.

Less experienced observers have complained that the binocular has too small a field, but I am reminded of the superbly designed (but very expensive!) Takahashi Astronomer 22 x 60 binocular which sported a field of view of just 2.1 angular degrees, so slightly smaller than that offered up by the Pentax 20 x 60! In truth, a 2.2 degree true field is perfectly adequate to frame the vast majority of celestial objects.

The binocular is ideally suited to framing showpiece deep sky objects for careful study, such as the Double Cluster, the Pleiades, the Beehive Cluster and other large Messier objects, but is also well appointed for use in comet hunting/observing and variable star work. Its high magnification and excellent contrast produces magnificent views of the Moon that will impress anyone who uses it.

The Pentax PCF 20 x 60 WP II can also be employed as a two-eyed spotting ‘scope in long-distance daylight viewing/surveillance, e.g. observing a bird’s nest at a comfortable distance or in a variety of maritime applications.

Its very reasonable retail price makes this a most attractive instrument for budget conscious amateurs who do not want to compromise on optical performance.

Highly recommended!

Post Scriptum: Stephen Tonkin, an accomplished binocular astronomer and author has written another review of this binocular (the newer SP incarnation). It can be viewed here.

 

Neil English is the author of several books on amateur astronomy. His latest work, Chronicling the Golden Age of Astronomy, is now availlable in hardback and electronic formats.

 

De Fideli.

A Survey of Binocular Astronomy Literature.

Every dedicated binocular enthusiast needs a good binocular guide.

Dedicated to Steve Coe (1949-2018)

As an enthusiastic, life-long collector and reader of astronomical literature, I’ve always appreciated the power and value of the printed word.

Having re-ignited a keen interest in binocular observing, I was somewhat saddened to see that many great works of binocular astronomy were being largely ignored by amateurs. To help redress this balance, this blog will take a close look at a number of books dedicated to the art of visual observing using ordinary binoculars, where I offer short reviews of a number of inexpensive works. Their value lies in the collective knowledge of the authors who have produced these works; experience that far exeeds those offered by the self-proclaimed ‘experts’ constantly chattering on internet forums. And you will save yourself a small fortune – time and money – by heeding their advice.

Exhibit A: Discover the Night Sky through Binoculars: A Systematic Guide to Binocular Astronomy.

Author: Stephen Tonkin

Publisher: BinocularSky Publishing

ISBN: 978-1-9164850-0-6

Price: £10

1st edition: October 2018, pp 145.

Want a good binocular guide for Christmas? I have the perfect recommendation for you! Stephen Tonkin’s new book is sure to appeal to binocular enthusiasts of all ages. Tonkin is no flash in the pan. He has authored or contributed to many books I’ve acquired over the years and writes a monthly column on binocular astronomy for Britain’s BBC Sky at Night magazine. He also maintains an excellent website dedicated to binocular astronomy, which can be accessed here.

So I was in no doubt about my expectations concerning his new offering and boy does it deliver! Though it looks like a self-published book, Discover the Night Sky through Binoculars, is a witty and authoratative survey of what can be realistically achieved with binoculars. After a short introduction, the first three chapters cover all the technical stuff you’re likely to need to know about how to get the best out of a decent binocular. There is a particularly humorous mention of some rubbish models, which Tokin refers to as “binocular-shaped objects.” He avoids making specific recommendations about specific models though, which is a good thing, as many units can now be purchased fairly inexpensively that can provide a lifetime of great astronomical views.

The remainder of the book is divided up into the many binocular sights arranged in a month by month sequence. His superlative first-hand knowledge of the heavens shines through as he clearly and effectively shows the reader how to locate each target. All the showpiece binocular targets are covered in this book, and many more besides. Though the sky maps printed in the book are a bit small to see well, one can always download higher quality maps from his website which you can study at your own leisure. I love his description of a phenomenon called pareidolia, which describes the psychological condition of seeing patterns in the starry heavens that are not really there!

I spotted one howler though; on page 8 he says, “our visual system evolved using two eyes.” Mr.Tonkin ought to look at this presentation by an expert on human vision before jumping to such conclusions! Tut tut lol.

It’s very easy to use this book, especially if you already have some experience of the night sky, but it will work equallly well for newbies. Indeed, it’s almost like having an expert right beside you as you make your own binocular observations. The end of the book features several useful appendices, whch cover important topics, such as how to determine the size of your dilated pupil, how to test your binocular for defects, as well as sound advice on how to maintain your binocular in tip-top condition over the months and years.

This is a great, no-frills book, with simple black & white illustrations, but it’s packed full of excellent observing projects that will keep you blissfully happy for many years to come.

Exhibit B: Binocular Highlights: 109 Celestial Sights for Binocular Users

Author: Gary Seronik

Publisher: Sky & Telescope

ISBN: 978-1-940038-44-5

Price: £18.99

2nd Edition 2017, pp 112.

Gary Seronik is no stranger to those who have enjoyed Sky & Telescope magazine over the years. He wrote a regular column; Binocular Highlights; for Sky & Telescope between 1999 and 2016, where he thereafter became the editor of the well regarded Canadian astronomy periodical, SkyNews. This neat little book features 109 objects from all over the northern sky that can be enjoyed with binoculars. After a good introduction, Seronik summarises all the things you need to know about binoculars and makes a specific recommendation that a 10  x 50 unit is probably the best compromise between power and portability. That said, he admits that he is an avowed fan of image stablised models, such as his favourite; a Canon 8 x 42IS.

The remainder of the book is divided up into chapters covering the four seasons of the year, where he presents a series of brief but very engaging mini-essays on the most celebrated of all binocular targets, concentrating on those objects that are best seen from mid-northern latitudes, though he does have an occasional entry of sights only visible in the deep south, such as the illustrious Omega Centauri. The book is lavishly illustrated throughout, with full colour charts typifying a 10 x 50 binocular view, on pages made from thin cardboard rather than regular paper, and is ring bound for convenient use in the field.

If I have any quibbles to make about this book, they are minor; I just wish he could have included more objects. That said, I suspect that, for the vast majority of observers, yours truly included, binocular observing is not really about pushing the envelope to observe overly difficult or challenging objects. The targets themselves are so beautiful that you’re likely to observe them many times during a season, where their orientation in the binocular field changes as they wheel across the sky. Thus, Binocular Highlights is designed for observers who just enjoy looking at the same objects as the season’s progress; and that’s fine.

Now in its second edition, Seronik has added 10 new entries over the original book, which is a bonus. In short, you can’t go wrong with this excellent little field guide but all the while, I can’t help but think those lovely coloured charts go a bit to waste when manhandled in the field.

Exhibit C: Stargazing with Binoculars

Authors: Robin Scagell & David Frydman

Publisher: Philips

ISBN: 978-0-540-09022-8

Price: £13.74(second edition)

1st edition, 2007, pp 208.

It is oft stated that the best way to start out in the fascinating hobby of astronomy is to purchase a good binocular. There is a great deal of truth to this sentiment. Many folk who express a casual interest in stargazing quite often become disillusioned by it, perhaps because they live in a heavily light polluted location, or they made the mistake of purchasing a large, complicated telescope that is just a pain to set up in the field. The wonderful thing about binoculars is that they are much more versatile than dedicated astronomical telescopes, since they can be used during the day to have a good look around, for nature treks, birding, camping, watching sports and the like.

Stargazing with Binoculars takes a much more pedestrian path through the fascinating world of binocular observing. Written by two veteran stargazers, Robin Scagell and David Frydman, who have amassed an enormous amount of field experience with more binoculars than you could shake a proverbial stick at. Their book, now in its second edition, shows you how the sky works and then presents a month by month overview of what can reasonably be seen using binoculars of various sizes. Unlike the aforementioned books, the authors include sections on lunar, planetary and solar observing, before engaging in a comprehensive survey of the binocular market. This is a great book to learn about how binoculars are made, what the various models offer the observer and how to test binoculars prior to purchasing. It also features an excellent chapter on how best to use a given binocular; whether it be hand-held, harness stabilised, or securely mounted in a variety of configurations, from simple monopods to complex binocular mounts.

Stargazing with Binoculars provides a wealth of information that any interested reader will find useful, including how to estimate binocular fields using star tests, making sketches of what one sees in a binocular, as well as sections on observing comets, meteors, artificial satellites and much more besides. It also provides a comprehensive overview of the southern sky, so it is equally useful to those observers who enjoy life in the antipodean.

This is a fabulous, cost-effective book for all binocular enthusiasts, featuring a generous number of full colour images to complement the text, and although I have not seen the second edition( 2013), I’m sure it will be just as good if not better. All in all, a great stocking filler for the binocular enthusiast!

Exhibit D: Observing the Night Sky with Binoculars: A Simple Guide to the Heavens

Author: Stephen James O’Meara

Publisher: Cambridge University Press

ISBN: 978-1843155553

Price: £24.99

2008, pp 148

I’ve always been a fan of Stephen James O’ Meara, a highly accomplished visual observer, who served on the editorial staff of Sky & Telescope for many years before joining Astronomy(USA) as a regular columinist. I have collected and enjoyed all of his books over the years and would heartily recommend them to anyone.

Though he is perhaps better known for his studies of deep sky objects, observing from the big Island of Hawaii using 4- and 5-inch refractors, I was glad to see that he produced a book dedicated to binocular observing to complement his telescopic adventures.

Observing the Night Sky with Binoculars is a large book compared with all the others mentioned above, with dimensions of 12 x 8″. The book opens with a great introduction to exploring the night sky, featuring the Big Dipper as a starting point to find your way around the sky. Here, you’ll learn how to estimate angular separations between objects, how best to perceive star colours, as well as a good introduction to the physiology of the human eye. A surprising amount of information can be gleaned by studying the Big Dipper and how it points to many other interesting objects nearby in the sky. What is somewhat surprising about this work is that O’ Meara categorically states that he used inexpensive binoculars – 7 x 50s and 10 x 50s – in preparing the material for this book. He does not dwell on the intricacies of binocular construction or advocate any particular brand of binocular, in contrast to his other books, where he strongly advertises the virtues of small, expensive TeleVue refractors(been there, done that, not going back).

The book continues by taking a seasonal look at the treasures of the binocular sky, covering each season from spring, summer, autumn and winter. What is immediately obvious is that O’ Meara has an encyclopedic knowledge of the mythology of the heavens, with a particular interest in ancient Egyptian sky lore. While this is all very good, I personally would have liked less discussion on mythology and more about actual observing, but everyone has their own take on how best to present the wonders of the night sky and, in this capacity, O’ Meara carries his own torch.

All the illustrations in this book are black & white, but the charts and diagrams are very easy to read and assimilate. In addition, there is a wealth of good drawings made by the author in this book which greatly adds to the value of this work and while many targets can be seen by the averagely keen eye, some are very challenging, requiring both very dark and transparent skies and a very keen eye to fully appreciate.

Though it is a bit more pricey than the other books discussed above, anyone with a keen interest in the binocular sky will appreciate this very well written book, and I for one feel fortunate indeed to have a copy in my personal library.

Exhibit E: Handbook of Binocular Astronomy: A complete guide to choosing and using binoculars for astronomers – whether beginners or not-so-beginner.

Author: Michael Poxon

Publisher: Starman Books

ISBN: 97809562394-0-2

Price: £12.96

2009, pp 397

Now for something completely different!

Michael Poxon is a name unknown to me, but that ought not deter a curious individual from investigating a book. Often times, to my growing knowledge, it’s ordinary folk who come across as being the most sensible and the most experienced, as opposed to the loud-mouthed guffaws you see on internet forums.

And Poxon puts his all into this very large book!

It begins, as all the others do, by stressing how important binoculars can be to the novice and dedicated astronomer alike. He offers sage advice in purchasing a good binocular, you know; what to avoid and what not to avoid. Curiously, he advises against image stabilised binoculars for the following reasons; they’re often very heavy(over a kilogram) and so do nothing to stave off arm ache, they rely on battery power(which he finds to be a nuisance) because they lose their charge in a few hours. They are also very expensive and the author feels that the money is better spent on conventional optics. Furthermore, he rightly points out that better stablisation can be achieved by using a homemade monopod. In this, I wholeheartedly agree; my brief experience with an image stabilised unit a few years back left me feeling a little underwhelmed and I felt the images were, let’s say a tad “artificial.” And although Poxon certainly advocates the cheap and cheerful porro prism varieties, he also sings the praises of compact, roof-prism models because of their labour-saving low mass in comparison to the former, albeit at some additional cost to the consumer. It is also clear that Poxon is a highly seasoned enthusiast, who has travelled to many places around the world to observe the binocular heavens. Ever the practical man, he has the presence of mind to include the construction of effective, low-tech dew shields for his 10 x 50s used during his prolonged binocular surveys, which he often mounts astride his 36cm telescope.

Chapter 2 deals with the basics of the celestial sphere, the magnitude scale of stars, as well as a very useful table indicating the magnitude limits, field of view and angular resolution of various popular models used by the amateur community. He also offers up valuabale advice on how much one can gain in stabilising a binocular; on page 31, for example, we learn that one can go a hefty 1.5 magnitudes deeper on a stabilised system compared with hand holding; and I’d call that signficant!

What follows are excellent general overviews of the Sun, Moon and planets, eclipses etc. Poxon does an especially good job in helping the reader recognise the many lunar craters and mountain ranges within the resolution remit of a typical 10 x 50 binocular with simple but very effective lunar maps. In Chapter 5 (which is mistakenly printed as Chapter 3), he delves into the fascinating world of deep sky astronomy and what follows is a very impressive listing of interesting variable stars, double and multiple stars (both wide and close-in) as well as a treasure chest of deep sky objects from the entire pantheon of constellations in the sky( the whole 88 are represented).The data is arranged in the form of notes which can be easily followed by the interested observer.

While the illustrations are not of the highest quality, they are generously presented and can be followed without much fuss. The end of the book contains a series of useful appendices with particular emphasis on variable star monitoring.This is an excellent book and, true to its opening lines, has something for every level of enthusiast; from newbie to veteran. I was pleasantly surprised by its excellent content, written by a well heeled amateur.

Exhibit F: Deep Sky Observer’s Guide

 

Author: Neil Bone

Publisher: Philips

ISBN: 0-540-08585-5

Price: £9.99

2004 pp 223

An honorary mention. The late Neil Bone(1959-2009) was a highly accomplished deep sky observer, public speaker and writer. A microbiologist by profession, he spent many of his evenings observing the glories of the deep sky from his Sussex home. Despite his notoriety and universal respect by the British astronomical community, Bone used simple equipment throughout his life, which included a ShortTube 80, a 10 x 50 binocular and a small Dobsonian telescope to accomplish all his observing goals. Deep Sky Observer’s Guide is a wonderful little book for beginning stargazers, featuring a rich selection of deep sky objects that are accessible to anyone with the same equipment. The first two chapters cover the basics of deep sky observing, including a great overview of the celestial sphere as well as the equipment and observational skills amateurs use to good effect to divine its many secrets. The rest of the book has chapters dedicated to particular deep sky real estate, including galaxies, asterisms, globular clusters, diffuse nebulae, open clusters, planetary nebulae and supernova remnants. Although the book is not about using binoculars per se, Bone used his 10 x 50 to make excellent observations of many of his subjects and are preserved for posterity in the pages of this literary gem. To see just what can be accomplished with a humble 10 x 50 binocular, this now classic text is a great place to spend some time. Many of the deep sky objects he describes were observed using his trusty binocular, and despite his premature passing, his rich word pictures still have the ability to inspire me. In amatam memoriam.

 

 

Exhibit G: Binocular Stargazing

Author: Mike D. Reynolds

Publisher: Stackpole Books

ISBN: 978-0-8117-3136-2

Price: £5.99

2005, pp 213

 

Mike D. Reynolds is a name familiar to many American and Canadian observers. A professor of astronomy and Director Emeritus at Chabot Space & Science Center at Oakland, California, he is probably best known for his popular writings in Astronomy Magazine, as well as his excellent books on eclipses and meteor watching. Binocular Stargazing is a very well written and thought-out book, covering a lot of ground. After a short foreword from celebrated comet discoverer, David H. Levy, the first three chapters provide all the information you’re likely to want to know about binoculars, past and present, written in a friendly yet authoratative style. What is very refreshing to see in this title is that, like nearly all the other authors of binocular astronomy, Reynolds emphasises that one can obtain excellent results with only a modest investment; a philosophy yours truly also shares.

Chapters 4 through 7 offer excellent overviews of how binoculars can be used for lunar & solar observing, before engaging in a thorough but non-technical treatise on the wider solar system objects, the distant stars, as well as presenting a great introduction to deep sky observing. One slight niggle pertains to the author’s persistent use of the term “pair of binoculars” throughout the book. Though certainly not a big deal and still used my many observers, the phrase doesn’t really make a whole lot of sense. The word ‘binocular’ implies duplicity. Better to use ‘binocular’ to refer to a single instrument and ‘binoculars’ when referring to more than one such instrument.

Chapters 8 through 12 offer up one of the best surveys of the binocular sky I’ve seen, arranged in seasons, ending with a special chapter devoted to observing from southern skies. Throughout, Reynolds displays his first-hand experience in the field and has a talent for making the subject matter very accessible. The science presentation is first-rate, as one would expect from a guy with an advanced degree in the science. Variable stars are particularly well represented in this title.

What I particularly liked is the inclusion of extensive appendices (A through I) at the back of the book. One appendix in particular, emphasises the age-old tradition of note-making and keeping, sketching and the like; an activity of great importance even in this age of instant digital gratification.

The text is quite generously illustrated in monochrome, though some of the images could have come out better, they are certainly good enough not to distract or confuse the interested reader. All in all, Binocular Stargazing is a highly recommended book for binocular enthustiasts, and I for one will continue to enjoy dipping in and out of it in the future.

Exhibit H: Touring the Universe Through Binoculars: A Complete Astronomer’s Guidebook.

Author: Philip S. Harrington

Publisher: Wiley

ISBN: 978-1620456361

Price: £18.34

1990, pp 306

It is hard to believe that nearly 30 years has gone by since the publication of Philip Harrington’s, Touring the NIght Sky with Binoculars. Back then, I was still an undergraduate with only a 7 x 50 porro prism binocular and a 60mm classic refractor to explore the night sky. Pluto was still a planet and the first CCD imaging pioneers were beginning to tinker with their crude chips to obtain electronic images of the celestial realm; most were still using photographic film. And while amatuer astronomy has changed beyond measure in only three decades, Harrington’s book provides solid evidence that some texts will never go out of fashion.

The preface of this now classic text reveals the modus operandi of the author, who admits that the book was primarily written for himself! Giving an honourable mention to Garrett P. Serviss’ 1888 work, Astronomy with an Opera Glass, Harrington weaves together an enormous body of field knowledge, which both complements and far exceeds the collective wisdom of his distinguished Victorian predecessor.

Harrington was one of the earliest amateur astronomers to call attention to the considerable advantages of using two eyes, explaining that gains of up to 40 per cent can be achieved in resolving fainter, low-contrast deep sky objects. This much is made clear in the short introduction to the book, but the march of time has thoroughly vindicated his binocular evangelism, as evidenced by the great popularity of binoviewing, as well the growth of binocular astronomy in general among the global amateur community.

The book, as Harrington makes clear, is actually a collection of concise notes which he himself compiled in his adventures under the night sky. Eschewing any discussion on equipment, the author launches into fabulous discussions of the Moon, Sun, planets and minor bodies of the solar system, before wading into the pantheon of objects existing far beyond our shores. Beginning in Chapter 7, Harrington provides concise but highly accurate depictions of a sumptuous listing of deep sky objects:- stars, open clusters, nebulae and galaxies, as seen in a variety of binoculars, both large and small.

In a departure from most other authors, Harrington recommends the 7 x 50 above the 10 x 50 as the best all round instrument for hassle-free binocular observing, but it is also evident that he has gained a considerable amount of experience behind a larger 11 x 80 instrument. Every constellation in the heavens is discussed separately, rather than approaching the subject from a season by season perspective. This works supremely well, being more reminscent of Robert Burnham Junior’s three volume work, Burnham’s Celestial Objects, than anything else.

While this hardback text was not designed to be used in the field, it is an indispensible work for planning and reflecting upon the sights seen on a clear, dark night. I find myself using it to compare and contrast it to my own observations and notes and to challenge myself to see more with a given instrument.

Remarkably, any discussions on binoculars per se are reserved for short appendices at the back of the book. Like all truly seasoned observers, Harrington avoids making specific recommendations, emphasing that one can do a great deal with modest equipment. Appendix B in particular, discusses how resourceful amateurs have hobbled together exceptional mounting strategies that greatly increase the comfort of viewing through truly giant binoculars, featuring such individuals as Norm Butler, Jerry Burns and John Riggs, to name but a few.

Although technology has certainly moved on (just look at the quaint photographs used to illustrate the text!) since Harrington first collated the work for this text, it is unlikely to be superceded by anything in the modern age. Indeed, it remains, for me, the definitive volume of binocular astronomy and shall continue to hold a special place in my astronomical library. Thoroughly recommended!

Concluding Words:

Just like in the case of telescopes, we are fortunate to live at a time in history where quality binoculars can be had for relatively small amounts of money. There is a bewildering number of models available to suit everyone’s budget, and even the least expensive units are immeasurably superior to the naked eye. But as all the authors of these books make clear, what is most important is that one gets out under a starry sky and use the instrument. Of course, one can decide to avoid the collective wisdom of these writers, but it will most likely lead the researcher down many dead ends (I speak from the well of my own experience), where one is tempted to keep buying ever ‘better’ models in the mistaken belief that grass is really greener on the other side. Unfortunately, this is largely the state of affairs on our telescope and astronomy internet forums, where folk seem to be more interested in a said instrument than actually using it. This is highly regrettable; indeed it is a very real kind of poverty, missing, as it were, the woods for the trees, but it can easily be countered by just getting on with the equipment we have.

I hope you have found these mini-reviews of some use and I do hope that amateurs everywhere will avail of these well thought out resources, written by people who have a real passion for observing the night sky and for sharing their knowledge with others.

Postscriptum:

Was it something I said?

Folk fae the fora having a guid chinwag about ‘binocular’, ‘pairs of binoculars’ etc.

Changin’ culture ken.

De Fideli.

 

 

Resolving Close Double Stars in a 12″ f/5 Dob during Cold Winter Weather.

Doudecim: the author’s 12″ f/5 Dob with a 8 x 50 achromatic finder astride.

 

Description of the Instrument:

Revelation Dobsonian, 305mm aperture with a focal length of 1525mm ( f/5)

Secondary mirror: 70mm minor axis, corresponding to a central obstruction of 22.9%

Primary and secondary mirror origin:  GSO

Primary mirror thickness(measured): 36mm (1.5″)

Mirror cell design: 9 point floatation system.

Both primary and secondary mirrors re-coated with enhanced HiLux coatings each with 97 per cent reflectivity.

Tube: Rollled aluminium, internally lined with a thin layer of cork and overlaid with standard flocking material.

Focuser: 2 speed Crayford style

Length of acclimation from room temperature to ambient: ~2 hours.

Fans used: none.

Finder: standard, straight-through  Revelation 8 x 50 model.

Method of collimation: collimation cap and Chesire eyepiece, verified with Hotech laser collimator.

Time required for precise collimation: 2 minutes.

Introduction:

The reflecting telescope reigns supreme in the 21st century as the telescope of choice for serious students of nearly all disciplines of amateur and professional astronomy. The reason is simple; in the case of Newtonians in particular,  they are, far easier to fabricate and mass produce than any other kind of telescope on the market, and are offered at sensible prices, allowing many people to fruitfully engage with the hobby. Today, an amateur can acquire a truly large telescope thanks to great advances in material science, where a thin layer of aluminium is vacuum deposited onto a carefully figured parabolic glass substrate, avoiding the problem of chromatic and spherical aberrations almost completely.

These days, it is not uncommon for an amateur to own extremely large aperture reflectors – in the 12 to 30 inch aperture class – at prices that don’t cost the earth. The development of the refractor, in contrast, has been severely retarded by the great difficulty and huge expense in producing optics of even moderate aperture. How many amateurs own an 8, 10 or 12 inch refractor? A little researching will soon reveal that very few of us would be willing to shell out the relatively enormous sums of money demanded by the few opticians willing to make them and even professional astronomers would laugh at the suggestion of replacing a large Newtonian or Cassegrain reflector to fund the installation of say a 10 or 12-inch ‘state-of-the art’ apochromat. As a case in point, this author vividly remembers an especially zealous refractor nut who openly called for the alumni of Universities to fund the installation of one such refractor. Not surprisingly, his clarion call fell on deaf ears.

Folk ain’t stupid.

While the Newtonian reflector has deservedly enjoyed a huge following from dedicated planetary and deep sky observers, their use in double star study has been artificially stunted by three decades of nefarious propaganda, instigated by individuals who clearly have little clue about how they behave when properly adjusted and acclimated. Like I said before, it’s easy to get a small refractor to ‘beat’ a large Newtonian if the latter is not adjusted correctly or has not been given enough time to cool down to ambient temperatures, but that hardly constitutes a fair test. Worse still, a subsection of the amateur community dismiss the Newtonian merely because they don’t look as ‘sexy’ as a long, slender refractor. Such individuals have reduced the hobby to something more akin to pornography than anything else. And you don’t have to look long to find it; check out the hysteria over this peashooter, for example. Has anyone not told them that a good 130mm f/5 or 6″ f/8 Newtonian would leave it in the dust, and for about half the price? Like moths to a lamp, they always seem to attract the same motley crew.

As a keen student of the history of astronomy, I have come across many cases where large Newtonian reflectors were used productively to pleasurably observe, or in some cases, even discover new double and multiple star systems. One need only look at the work of such luminaries as Sir William Herschel, Warren De la Rue, Sir William Lassell, the Reverend T.W Webb, William Denning and T.H.E.C. Espin, to name but a few, to see that the Newtonian reflector has been a very productive telescope in the divination of double stars, both for pleasure and for scientific gain. The archives of these historical figures reveal many extraordinary feats of resolution achieved with the Newtonian telescope.  And it is to these individuals that this author has turned to for guidance and inspiration.

Having left the world of small refractors behind, apart from my fabulous achromatic binos and my little ShortTube 80, I set out on an ambitious program of field testing Newtonian reflectors of ever increasing size, having gained intimate experience with the behaviour of the said telescopes in the 3, 5 and 8 inch range, firmly establishing that they are excellent double star instruments. What is more, this author has found through his own experience that a good 8 inch f/6 Newtonian reflector is a much better double star telescope than an optically excellent long focus classical refractor of 5 inch aperture and f/12 relative aperture.

These personal discoveries have led me to more closely investigate the performance of an even larger Newtonian reflector, a standard 12-inch f/5 Dobsonian, which has not enjoyed nearly as much field use than it should have since it was first acquired a few years ago. The limelight was firmly stolen by the smaller instruments, which are easier to deploy in the field, acclimate faster and are less sensitive to the vagaries of the atmosphere, but no more so than with a refractor, or indeed, any other kind of telescope, of the same size. That being said, I have enjoyed many wonderful nights where the traditional bugs that attend Newtonians were either minimal or non-existent, allowing me to obtain truly spectacular views of a suite of double stars traditionally considered ‘tricky’ by my astronomical peers.

In this capacity, this short blog will exemplify the techniques used and the results obtained in observing double stars with such a large, fast telescope.

Method:

What follows is a report of one night- January 8 2019 – between 22:00 and 23:10 UT

Ambient temperature: 0C at 22:00 UT falling to -1C by the end of the vigil at 23:10UT

Conditions: Slightly hazy, no wind, steady atmosphere (Antoniadi II), very cold.

The telescope was brought out from a warm, dry, indoor environment and left to passively cool for 2 hours before the commencement of observations. Though it is fully acknowledged that cooling fans can accelerate the acclimation process and help scrub away the boundary layer on the primary mirror, no such fans were used in keeping with the procedures of the aforementioned historical figures, none of whom had access to (or knowledge of) such fans.

Observer; suitably attired for cold weather observing; several layers of clothing; vest, jumper, overcoat, hand gloves, hat( me ole beanie). No dew shield used.

The following systems were examined in the 12″ f/5 Dob:

Theta Aurigae; a greatly unequal double, primary (A) , magnitude 2.6, secondary (B) magnitude 7.2. Separation 4″.

Iota Cassiopeiae: Triple system: AB- magnitudes 4.6 and 4.9 separated by 2.6″

AC: magnitudes 4.6 & 9, separation 7.1″

Eta Orionis: AB: magntidues 3.6 and 4.9; separation: 1.6″

Eta Geminorum (Propus): AB: magntidues 3.1 and 6, separation ~1.7″

52 Orionis: Classic Dawes pairing; AB equal 6th magnitude components, 1″ separation.

All systems observed either naturally or using a Baader single polarizing filter which cuts glare and increases contrast without imparting a colour shift to the stellar components.

Power employed: 277x throughout (Meade Series 5000 5.5mm UWA ocular).

Results:

The telescope resolved all 5 systems beautifully. The enormous resolving power and light gathering capability of the 30.5cm Newtonian made observing them especially thrilling. While there were many moments during the observations where the stellar images broke up or swelled slightly, there were also many opportunities where the images came together, producing text-book perfect results. As aperture increases, the size of the Airy disk shrinks, allowing the faint, close in companions to be more readily seen.

Iota Cassiopiae was quite simply stunning! All three stars appeared very bright and round as buttons in the 12 inch telescope at 277x. I have not personally experienced a better view of this triple system. Unequal pairs were always more challenging owing to the glare of the primary components, but still readily observed.

Propus(Eta Geminorum); is a particularly difficult system to crack, but on this evening the faint close-in companion presented better than I have ever seen it in my 8″ f/6 Newtonian at any power; the sheer resolving superiority of the 12 inch instrument clearly strutting its stuff.

A polarizing filter screwed into the bottom of the 1.25″ ocular significantly improved the aesthetic of the images by reducing glare and increasing contrast (read darker sky hinterland) very reminscent of a large refractor. Indeed, the filter made it significantly easier to prize the faint companion of Propus and Theta Aurigae in the same instrument.

The closest pairing observed on this evening – 52 Orionis – produced an image that was in a completely different league to any of the smaller Newtonians I have enjoyed testing. The components were much brighter, easier to see with lots of dark space between the components.

All in all; a very good short session under the starry heaven!

Discussion:

The Newtonian reflector has clearly come along way since it was first conceived of by Isaac Newton in the late 1600s. And while speculum metal allowed great gains to be made in both amateur and professional astronomy circles, it may surprise some readers just how far the reflector has been intelligently re-designed ever since those glory days of the past. Did you know, for example, that according to the studies of Dr. Wolfgang Steinicke, an expert on the telescopes at Birr Castle, that the 72 inch Leviathan of Parsonstown had a light gathering power equivalent to a modern, state-of-the-art 25 inch Newtonian reflector [see my book Chronicling the Golden Age of Astronomy,  as well as chapter 7 of William Parsons, 3rd Earl of Rosse: Astronomy and the Castle in Nineteenth-Century Ireland (Charles Mullan ed. 2016)]. Seen in this light, this author considers himself very fortunate indeed to have acquired such a great telescope as the 12 inch f/5 Dob for just a few hundred pounds( it was second hand).

The reader should note that these results are not at all exceptional. Indeed, the author has clocked up many similar nights where the full power of the 12 inch can be pressed into service. Neither is the author out to set any records; the closest pair thus far resolved has only been ~ 0.7″ but the same instrument is fully capable of resolving significantly closer pairs should he wish to pursue them. These results are wholly consistent with the historical archives of many of the early observers mentioned in the introduction, who managed to split extraordinarily close pairs with telescopes of broadly equivalent aperture. For example, T.W. Webb was able to resolve the components of Eta Coronae Borealis using his silver-on-glass 9.5 inch f/8 With-Berthon Newtonian, which had a separation of 0.55″ in the 1870s. Such results make it patently clear that such work can be acheived with larger Newtonians, with excellent results.

Focusing is very challenging in such a fast telescope as the f/5 Reveation Dob. The author very much appreciates the fine focus on the dual-speed Crayford that came with the ‘scope. At f/5 it is a very worthwhile tool in attaining the most precise focus possible.

Filters, such as the Baader single polarizer, are very useful in attaining the right balance between image brightness and contrast. The advantage of using the latter filter is that it does not impart a colour shift to the stellar images, allowing the observer to record the pure colours of the component stars. Using a blue filter will also help resolve the very tightest pairs, as the resolving power of the telescope scales inversely as the wavelength of light used to probe the system. When you have access to such a large telescope, it collects so much light that productive work with even deeply coloured(read low transmittance) filters becomes very worthwhile.

As always, the author would encourage others who have access to such a large Dobsonian to give such systems a try. When careful attention is givien to both collimation and acclimation, the sky’s really the limit!

Thanks for reading and keep looking up!

 

If you liked this blog and wish to support the author, please consider buying a copy of his new book: Chronicling the Golden Age of Astronomy, newly published by Springer-Nature(available in both hardback or electronic formats).

 

De Fideli.

 

 

The Lockyer Sequence

New year’s Day 2019: Plotina starting well on a trail first blazed by Sir Norman Lockyer(1836-1920).

On the evening of January 1 2019, I set up my 130mm f/5 Newtonian astride its Vixen Porta II mount. Conditions were cold, still, and frosty, with temperatures between 0 C and -2C. Seeing was judged to be very good (Antoniadi II).

My purpose this evening was to examine a half dozen double and multiple stars in Orion, as suggested by the distinguished Romanian observer, Mircea Pteancu, who kindly alerted me to a reference made by Norman Lockyer et al in their book, Stargazing: past and present (1878). On page 164 of that book, the authors describe a sequence of double and muliple stars in Orion, which present systems of varying degrees of difficulty for the curious telescopist. After careful collimation and adequate acclimation, the 5.1″ reflector was turned toward the Celestial Hunter, beginning at about 22:00UT and the following systems examined at magnifications ranging from 118x to 566x. The results are shown below:

The Lockyer Sequence.

 

Notes:

The times and magnifications employed are displayed beside the drawings, which depict their orientation in the Newtonian reflector. For all sketches, south is up and west is to the left.

Teasing the close companion to Zeta Orionis apart from its brilliant primary did prove quite tricky, but with a concentrated gaze during the stiller moments, it did yield to the 130mm telescope. The reader will also note the much fainter(10th magnitude) shown at the lower right of the sketch.

The most challenging proved to be 52 Orionis(1″ separation), but with its decent altitude at 22: 43UT, I was able to resolve this classic Dawes pair ( twin 6th magnitude components)  using very high powers. Intriguingly, I first attempted this system by coupling a Meade 3x Barlow lens to a 4.8mm T1 Nagler yielding 405 diameters but without much success. The image was quite dim and very difficult to see the components distinctly. As an experiment, I switched to a Meade Series 5000 5.5mm ultra-wide angle ocular, coupling it to the same 3x Barlow but I also screwed in a 1.6x Astroengineering 1.6x amplifier yielding a power of 566x. To my great surprise, I found the image of the system to be significantly brighter than with the old Nagler and it was much easier to prize the components apart. I can only suggest that the better (read more modern) coatings on the Meade 5.5mm ultra-wide angle allowed greater light throughput, despite the higher powers employed.

566x represents a power of 111x per inch of aperture.

The 130mm f/5 Newtonian continues to surprise and delight me. It’s small, high-quality optics, thermally stable (cork-lined) closed-tube design, and ease of attaining perfect collimation all contribute to its efficacy as a medium-aperture double star instrument.

I would encourage others who have similar equipment to give these beautiful systems a visit. What better way to entertain and challenge a dedicated observer on a cold winter’s evening!

 

 

De Fideli.

A Winter Adventure with a 130mm f/5 Newtonian.

Plotina; the author’s 130mm f/5 Newtonian doing its stuff under a Christmas sky.

Sunday, December 23 2018

With the Christmas holidays now upon us, we were lucky enough to enjoy a beautiful  winter day, with clear blue skies illumined by a feeble Sun. This time of year, darkness falls very early, well before supper time, and as luck would have it, the sky remained clear after dark. I decided to field my trusty 130mm f/5 reflector, mounting the telescope on an old Vixen Porta II mount at about 4.00pm local time, and let it cool down to ambient temperatures, which had already reached 0 C by sunset. Accompanying the telescope was a 8 x 42 roof prism binocular, used for finding fainter objects more quickly than with the telescope and its finder alone.

The cold weather was never a concern though; afterall, the telescope has strutted its stuff many times in sub-zero temperatures, as I’ve described in many previous blogs. At 4.45pm I began my observations with a look at the Red Planet, Mars, which by now had greatly receded from the Earth, but at least had now reached a very decent altitude in the south. Inserting a Parks Gold 7.5mm eyepiece coupled to a Meade 3x achromatic Barlow lens yielding a power of 260 diameters, I was greeted by a tiny little salmon-pink orb, quite obviously gibbous in cast, with a few dark markings visible across its surface. The view was good and steady and very satisfying given the great distance to which it had receded to since its glory days during the summer, when the planet swelled to an enormous size as seen through the same telescope.

But what I was really after this evening was a suite of double stars, my staple observational targets for many years now. Having abandoned small refractors and Maksutovs for the greater efficacy of the 5.1 inch Newtonian reflector, I turned the instrument on Epsilon 1 & 2 Lyrae, a summer favourite, but still suitably placed for observation in the early evenings of December. Keeping the same eyepiece and Barlow in the focuser, I obtained a wonderful, text-book perfect split of all four components. And though I had seen such an apparition more times than I care to remember, it still brought a broad smile to my face to see these old friends in a Christmas sky.

From there, I moved over to Delta Cygni, a much better test of atmospheric turbulence than the four stars of Epsilon Lyrae. Carfeully centring and focusing the bright white luminary, I obtained an excellent and stable image of the faint, close-in companion at 260x. It was at that point I knew that conditions were good enough to attempt the trickier targets that were lining up in the sky.

Moving the telescope further west, I could see bright Altair, so I tried my hands at the difficult and faint Pi Aquliae nearby, which I first reconnoitred with the 8 x42, before centring it in the 6 x 30 finder ‘scope of the main telescope. Keeping the power at 260x, I achieved a reasonable split of these fairly closely matched components but I could see that it was noticeably inferior to how it looked in the late summer and early autumn, when it was higher up in southern skies. Still, I was well chuffed to have bagged this system so late in the season.

Moving several degrees east into the diminutive but lovely constellation of Delphinus, I immediately aimed for the jewel of the celestial Dolphin; Gamma Delphini. The 5.1″ reflector made light work of this easy but fetching double star which was best seen at 118x using my Meade 5.5mm Ultra-wide angle eyepiece. From there, I sped over to Cygnus again and quickly located the multiple star, o^1 Cygni using the 8 x 42. Training the telescope on the system brought another huge smile to my face, as the beautiful and wide colour constrast triple system came to a perfect focus, their tiny Airy disks and faint first diffraction rings calmly presenting themselves in the frigid air.

After that, I panned the telescope eastward until I centred Almach (Gamma Andromedae) in the 118x eyepiece and was greeted with a beautiful split of this comely, colour-contrast double star. Even after all these years of observing it, it never ceases to inspire me! “That was easy,” I said to myself, ” but let’s have a go at a much more tricky system.” With that thought I trained my binocular at a patch of sky in eastern Cygnus, specificially looking for a faint pair of stars, the brighter of which was Mu Cygni. Quickly aligning the telescope on the same patch of sky, I inserted the 260x eyepiece-Barlow combination described earlier and carefully focused. Voila! There it was; a wonderful text-book perfect split of this very close binary system, with the wider, fainter star visible in the same field comprising the triple.

Finally, I visited the endlessly lovely Albireo, now fairly low in the western sky. Needless to say, it was a sight for sore eyes. It’s true; some of the most beautiful objects in the night sky are the easiest to access!

So far, so good. I took a break for a few hours, enjoying a good, traditional Christmas roast with my family, keeping the telescope in an unheated outhouse all the while, so as to allow me to quickly engage with the night sky. Beginning again around 10:15pm, with the bright Moon having risen in the sky and the temperatures having dropped to -2C, I  started in Orion, which at the time of observation, had still not culiminated in the south. Hoping for a continuation of the steady skies experienced earlier in the evening, I trained the 130mm Newtonian on mighty Rigel. Slightly anxious, I carefully focused the bright white luminary in the 118x eyepiece and was relieved to see that the primary Airy disc was small, round and virtually free of turbulence. And there beside it was the tiny spark from its feeble, close-in companion. It was a beguiling sight!

From there I moved a wee bit to the northeast and centred Eta Orionis.This is a more difficult pair to resolve and so requires higher powers to tease apart. But at 260x it was easy; the two stars, plain white to my eye, appeared roughly east to west in orientation.

By now, mighty Auriga, the Charioteer, had risen to a great altitude, high in the east, and so I turned the telescope on its most prestigious double star; Theta Aurigae. The telescope made light work of this tricky system, the faint, steely grey companion being stably held in the frosty air.

A night of winter double star observing could never be complete without a quick look at Castor A & B in Gemini. Just east of the bright, near-full Moon, I had to battle with the glare a bit before centring the system in my 6 x 30 finder ‘scope. But at 260x, the twin white stars, pure as the driven snow, was a msemerizing sight in the telescope; the Airy disks small and round as buttons, each surrounded by a single, faint diffraction ring.

Finally, I thought I would try my hand at 36 Andromedae, which was first found with a bit of ferreting around using the 8 x 42 binocular. And sure enough, I was able to split this 1 arc second, near equally bright pair in the telescope without much effort at 260x. However, it was better seen using the higher power of a 4.8mm T1 Nagler eyepiece coupled to the same 3x Barlow yielding 408x. I was mightily impressed with just how good and stable the image remained as it shot across the field of view at this ultra-high power.

Vigil ended shortly before 11pm local time.

What a great night!

Simple pleasures with a simple telescope!

The stuff dreams are made of.

 

De Fideli.