A work commenced November 11, Anno Domini 2019.
Subject to Copyright
I’m a big fan of pocket binoculars; they’re tiny, elegant, and when decently made, are very sharp shooters. Compared with standard-sized binoculars, ‘pockets’ are much less expensive and there is a good one available to suit most anyone’s budget. They can work well with kids, grand-parents and every one in between. Their extreme portability makes them very popular across a broad ecclesia of people; hikers, birders, sports spectators, hunters, theatre goers and general nature lovers. They’re as likely to be found near a window overlooking a garden as they are tucked away in a backpacker’s pouch. But what is less commonly known is that they can be used for casual astronomical viewing. Unlike telescopes, there is no set up required. Simply pick it up and off out you go! They’re so small that they are completely immune to the vagaries of the Earth’s atmosphere. It doesn’t matter if the seeing is horrid or immaculate, their small apertures and low magnification will show you the same view, under the same conditions, time and time again. Their very low carrying weight allow individuals to hold them to their eyes much longer than standard binoculars in the 40 to 50mm aperture class. And as soon as you’re done, they fold away in a pocket, hence the name.
Pocket binoculars are almost invariably not recommended for astronomy. Sure, they don’t provide those knock-out views you get with larger binos, but what if your only instrument were a pocket binocular? Is viewing the night sky anathema? Absolutely not! Even small glasses like these can bring a great deal of cosmic real estate to your eyeballs. And though their ability to gather faint starlight is limited, they will nonetheless greatly exceed the acuity of even the keenest, sharpest human eye.
I suspect that one of the main reasons why pocket binoculars are not spoken of much in astronomical circles is that most people live in big cities or towns, where light pollution drowns out much, if not all, the glory of the starry heaven. They are disconnected from the great natural light show provided by Amighty God, who reveals His majesty in every shooting star, every burning sun, every moon, planet, and galaxy scattered across the Universe. But if you take leave of the cities and drive out into the countryside, the night sky is transformed from a washed-out, featureless dome into a marvellous light show that can fill us with awe and re-unite us with the sacred, the mysterious and the infinite-eternal.
I have the immense good fortune to live in a beautiful place, far enough away from the large cities and towns that are home to the vast majority of people. I can step out of my back door and immediately engage with the sky. I take nothing for granted. For me, astronomy is not always connected with darkness. In Scotland, we enjoy many fabulous sunsets, painting radiant colours; brilliant oranges, sanguine reds, and even purple splashes across the heavens as the Sun makes its way toward the horizon. As dusk gives way to darkness, the night sky has a way of wrapping itself around you like a magic cloak. At first, only the brightest stars can be seen, but as full darkness falls upon the landscape, the great host of heaven come out to play. Being located on the western edge of northern Europe, beautiful auroral displays are common, colouring in the northern horizon in magnificent ribbons of incandescent light. Out here in the sticks, the great river of stars that constitute the Milky Way can be easily seen on a dark, Moonless night.
During deepest winter, darkness rules. The Sun sets early(4pm) and rises late(8am). Many go to work in darkness and travel home in darkness. Yet in summer, the Sun rules the sky from 3.30am to after 9pm, and even then its shallow dip below the northeastern horizon never brings true darkness. In June and July, twilight rules the wee small hours. Still, whether it’s high summer or deepest winter, my pocket binoculars never fail to show me something new and exciting.
My quest to find a good pocket binocular encountered many unexpected twists and turns. I don’t live anywhere near a good binocular dealer, so I was not afforded the luxury of ‘trying before you buy,’ as it were. No, in my case, the best I could do was ‘buy-in and try.’ Some models promised the earth but fell well short of the mark. In other cases, I trusted the opinions of a number of so-called ‘experienced glassers’, but upon learning how to test such instruments myself, I discovered that many of these reviews were just not discriminating enough. It was like deja vu all over again from my telescope testing days( I have no interest in acquiring any new telescopes, as I already have all I could possibly wish for). Some models advertised as ‘premium’ turned out to be junk.
In the end though, I settled on a couple of models – both 8 x 25 formats – made by reputable firms; Zeiss and Opticron. Unlike a swathe of pretenders, these were the real McCoys. Both models are very well made, with fully-multicoated optical components and phase corrected Schmidt-Pechan roof prisms. The Opticron has a wonderfully flat field of view, thanks to the incorporation of aspherical ocular lenses, but the size of the field is rather restricted as modern pocket binoculars go; just 5.2 angular degrees. In contrast, the Zeiss Terra has a significantly wider field – 6.8 degrees – but is not quite as sharp at the edges of the field as the Opticron. During daylight testing, I ascertained that the Zeiss Terra produced a slightly brighter image, due in most part to the employment of higher reflectivity dielectric coatings on the prisms. The Opticron, in contrast, has silver coated prisms, with slightly lower reflectivity.
Both models display excellent control of stray light and do not produce annoying internal reflections and glare when pointed at bright objects like the full Moon, or during the day, when glassing strongly backlit scenes. This affords the highest levels of contrast in the images they produce. For astronomical use, where all the objects are effectively located at infinity, it is important for the field to remain as flat as possible from the centre right the way to the edge for aesthetic appeal. While many of the pretenders I tested were good on axis, their edge of field definition was less than desirable. And no one wants to see stars bloat to enormous sizes as they are moved off axis.
Both models have hermetically sealed optics, filled with dry nitrogen gas at a slighly higher pressure than the surrounding atmosphere. This prevents fogging of the optics in cold weather and slows down internal corrosion of the components. The slight pressure differential also creates a small outward force that helps keep dust and fungi from entering the instruments. Ergonomically, the Zeiss is easier to use, as its slightly larger frame fits my hands that little bit better than the Opticron. Both focusers are buttery smooth with zero backlash when rotated clockwise or anti-clockwise, but this has proven more important during daylight observing than at night, where relatively little focusing adjustments are required, as for example, in moving from a target at low to high elevations above the horizon. The Opticron is the more elegant instrument; the Zeiss more rugged.
Mechanically, both the Zeiss and Opticron are very well endowed. The double-hinge design on both models has enough tension to maintain my particular inter-pupillary distance, and fold up with ease when not in use. The eye lenses are good and large on both instruments, allowing me to comfortably and swiftly engage with the entire field, with little or no guesswork or blackouts. The eyecups on both instruments are robust, comfortable and simple to deploy. Unlike other models which offer several positions, both the Zeiss and the Opticron only have two- either fully down or fully up. So, not ot a lot to think about, less and thus less likely to distract, therefore more useful. And both have the same eye relief; 16mm.
The larger field of view of the Zeiss(6.8 degrees) is more useful for daytime applications, but at night, when observing the sky, even a 5.2 degree field is more than sufficient to frame the vast majority of targets I’m likely to study. I estimate that the limiting magnitude of both instruments to lie somewhere between +8.7 and +8.9. And with the same exit pupil – 3.1mm – they allow me to image targets with the sharpest part of my well designed eye lenses.
A Walk through the Autumn Sky:
November is perhaps my favourite month. It’s easy enough to justify. I entered the world in November, and have come to associate my experiences of it with the carefree days of my youth. While the trees begin their long winter slumber, I feel especially alive. All my senses go into overdrive. Maybe it’s the vibrant colours of autumn leaves that assault the eyes, or the sweet, musky aroma of decaying plant matter that infuses the misty air. Or could it be the crunching sound made by my feet as they wade through the rain-soaked leaf litter that creates a memory trace back to the innocence of childhood? Whatever it is, walking though the rural autumn landscape upwells deep feelings of reverence for the preternatural beauty of the wet and the wild.
The feeble light of November compels me to re-schedule the times of my walks, and usually I try to make the most of the daylight by venturing out around noon, when the Sun is at its highest in the sky. And though November nights can be mild, bitterly cold, and everything in between, the celestial treasures that attend a clear night with no Moon greatly warm the heart.
To help us find them, it pays to invest in a good literary guide and, in this capacity, I would heartily recommend Ian Ridpath’s and Wil Tirion’s, Collins Stars & Planets, now in its fifth edition. In it the student of the starry heaven can find all kinds of useful information, packed full as it is with month-by-month maps of the entire night sky, as well as beautifully illustrated colour maps of all 88 constellations that grace the celestial sphere.
Heralds of Winter
So without further ado, let’s begin our adventures with a pocket binocular. A great place to start is to seek out two amazing sights in the northern heavens; the glimmering Pleiads and imposing Hyads, both located near each other, and both well situated for observation, riding high in the sky after 9pm on mid-November evenings.
Before we embark on our first celestial adventure, let’s get suitably attired by reading the celestial swangsong of Lord Byron(1788-1824):
‘Tis midnight! on the mountains brown
The cold round moon shines deeply down;
Blue roll the waters, blue the sky
Spreads like an ocean hung on high
Bespangled with those isles of light,
So wildly, spiritually bright.
Whoever gazed upon them shining,
And turn’d to earth without repining,
Nor wish for wings to flee away,
And mix with their eternal ray?
From Night at Sea by Lord Byron.
Both the Pleiades and Hyades, the heralds of winter, are easy to find in the November night sky. Both are located in the zodiacal constellation of Taurus. The Hyades is readily identifiable as a distinctive V-shaped asterism with a bright orange coloured star, Aldebaran, marking the southeastern-most tip of its horns, and a little higher up and to the right of it you’ll see the glittering jewels of the Pleiades star cluster. Known by many names throughout antiquity and even further back into the long human pre-history, the Pleiades appears as a tiny congregation of stars, rather like a miniature Plough with a somewhat truncated handle. For me, the most inspiring references to the Pleiades are sourced from God’s very own love letter to humanity; the Holy Bible. In all, the gleaming Pleiads are mentioned three times in the Good Book, twice in Job (9:9 & 38:31) and once in Amos(5:8), where the King James Version mentions them as “the seven stars”. The Lord God Almighty challenges his servant, Job, by asking him if he can “bind the sweet influences of Pleiades?” The implication is clear; no human can do such a thing, but it’s all in a day’s work for his Creator.
With my average eyes, I can usually make only six members from my home. But at darker sites, with better transparency, I have occasionally chanced on the seventh member – whence its nickname of the Seven Sisters – though still with considerable difficulty. That said, there are many accounts of people seeing more than seven members with the naked eye. For example, from the summits of high mountains, where the air is thinner and (often but not always) less turbulent, reports of seeing as many as 10 or 12 members are not uncommon in the archives. I know of one account, published in the Astronomical Register from October 1883, where astronomers at the newly established Pic Du Midi Observatory in the French Pyrenees, at an elevation of about 9,500 feet, reported the detection of 16 members with the naked eye!
Through the pocket binocular, the Pleiades never fails to inspire. Instead of straining to see six members, several dozen are plainly presented covering the central third of the binocular field. And though the view is immeasurably improved by looking through a larger binocular or small telescope, I cast my mind’s eye back in time to when the Italian astronomer, Galileo Galilei, first turned his primitive spy glass on the same cluster of stars in 1610. Though the field of view of his telescope was woefully small (about one quarter of an angular degree, or half a full Moon diameter), Galileo still managed to record the main stars of the cluster, which are spread across one and a half Moon diameters. That’s something I have done before when I was sketching the Double Cluster in Perseus using a large Maksutov Cassegrain, sporting a field of view of only half an angular degree. It’s challenging but it’s certainly doable!
The number of stars visible in the Pleiades depends on a variety of factors; the amount of light pollution you encounter, the transparency of the air you’re looking through, as well as its elevation above the horizon. I find the latter factor particularly interesting, as I have watched the Pleiades from its heliacal rising in the east in the wee small hours of August nights, right the way through to late spring, when it is observed sinking ever lower in the west. When the cluster is glassed close to the horizon, only the most brilliant members are clearly discerned with the pocket binocular. For example, when observed at just 10 degrees above the eastern horizon, the dense canopy of air you’re looking through will dim the brilliance of the cluster by nearly one stellar magnitude! But if you venture out later in the evening, when the cluster has reached say 30 degrees altitude, you’ll gain an extra half a magnitude and your little binocular will begin to to show many fainter members. So, the higher the cluster rises in the sky, the better the view you will experience. This is equally true of any astronomical target, so it always pays to wait until your binocular target is well above the horizon; patience is a virtue!
The brightest luminaries of the Pleiades have beautiful names, inspired by the mythology of classical antiquity; Merope, Pleione, Electra, Asterope, Maia, Celaeno, Alcyone, Taygeta and Atlas, which you can see on page 241 of my guide book referenced earlier. The pocket glass reveals that they all have a silvery white colour, that betrays their relatively young age, which astronomers estimate to be about 50 million years. The centre of the cluster is estimated to be located at a distance of about 450 light years.
If the Pleiades fail to inspire, then surely the majestic Hyades can? To see it, cast your gaze at the bright orange star Aldebaran and bring the pocket glass to your eyes. What you will see is a large V-shaped asterism filling most the field of view of the pocket binocular. These are the ‘horns’ of the celestial Bull, with Aldebaran situated in the south east of the field. Like the Pleiades, the Hyades is also steeped in ancient Greek mythological lore(but mostly pagan). Indeed, the Hyades were the fabled daughters of Atlas and Aethra, and half-sisters of the Pleiades.
When situated high in the sky, the Hyades is a marvellous sight in the pocket binocular. If you take a long, studied look at it with dark-adapted eyes, you will begin to notice that there are other red stars in the field, specifically, the three brightest stars that delineate the upper(northernmost) horn of the Bull. Its other stellar constituents appear white or blue-white to my eyes.
In order to create more atmospheric scenes, it pays to seek out some trees over which the Hyades and Pleiades appear to hover. Even on a dark night, the silhouette of tree branches set against these illustrious autumn clusters can be easily made out and adds greater dimensionality to the binocular view. I also love to observe these clusters as they change their orientation in the binocular field, rising in the eastern hemisphere, culminating in the south, before falling back towards the western horizon.
By the time the Pleiades and Hyades have reached a good altitude in the sky, the constellation of Gemini will be seen rising above the eastern horizon. But just as the full Moon often appears larger to the naked eye when it is close to the horizon, the same is true of the relative positions of the stars. Though seldom(if ever?) discussed in the contemporary astronomical literature, the illusion is known as the horizon enlargement effect. This can be perceived rather easily when observing the two brightest luminaries of this constellation; Castor and Pollux. If you see these stars rising in the background of a distant landmark, such as a hill or a building, they will appear to be more widely separated than when they are situated higher up in the sky. The effect is quite dramatic, though still illusory. That said, the little pocket binocular always shows them to be the same distance apart, no matter where they are situated in the night sky!
This curious effect was discussed over a century ago in an interesting article penned by Dr. Edouard Claparede, which first appeared in the October 1905 edition of Archives de Psychologie, and which was subsequently discussed in a short communication published in the journal Nature dated February 22nd 1906, in which it is stated:
He(Dr. Claparede) arrives at the conclusion that when we see the moon or sun, at the horizon, we are surprised into believing it to belong to things terrestrial – to come into the class of objects which are by far of the greatest interest to us. As such we notice it with much greater attention, and for this reason overestimate its size.
But there is yet more illusion associated with Castor and Pollux, the so-called celestial twins, than that presented by the horizon enlargement effect. Situated exactly 4.5 angular degrees(or 9 full Moon diameters) apart, both stars easily fit in the field of the view of my pocket binoculars, but if you look at their colours they will be seen to be completely different; Castor(located higher up in the sky) is white, pure as the driven snow, while Pollux(lower down) presents as orange in contrast. What is more, Pollux appears distinctly brighter in the pocket glass than Castor(and to the naked eye for that matter!), though their designation is opposite to what one might expect in that the brightest star in a given constellation is usually assigned the Greek letter alpha, and the second in glory, beta and so on. The reason lies squarely at the feet of the Johann Bayer(1572-1625) who wrongly assigned the Greek letters to these stars in 1603 in his magnum opus, Uranometria Omnium Asterismorum, seemingly unaware that Castor was fainter than Pollux. In fact, Castor, with a visual magnitude of + 1.6, is assigned to the second tier of stellar glory, while Pollux, at +1.1 is a bona fide 1st magnitude sun.
Curiosuly, Bayer’s blunder was not unique to his good self. Many celebrated astronomers through history estimated both stars to be of the same degree of glory(2nd magnitude); Hipparchus, Tycho Brahe and Hevelius, to name but a few. And closer to our own time, Argelander(1840) and Heis(1860) though accurately assigning Pollux to +1.1, designated Castor a value fully half a magnitude fainter than it really is (+2.1). Only with the invention of the photometer in the 1860s did these discrepancies become resolved.
Looking at these stars through the pocket binocular, or any other optical accoutrement for that matter, one is hopelessly unaware of their distances from the solar system, which astronomers have estimated to be 52 and 34 light years for Castor & Pollux, respectively. And neither could they realistically be expected to have been formed from the same stellar nursery. What is more, though the apparition is quite beyond the capabilities of these tiny binoculars, Castor is a fascinating multiple star system of which, the two most prominent are closely separated stars, designated A and B, both roughly three times the mass of the Sun and of an early spectral type A, with an estimated age of 370 million years. Through a small telescope at high magnification, they make a splendid visual target, easily resolved in this epoch(2019) in even a humble 60mm refractor. Pollux on the other hand, is a more highly evolved orange giant star, nearly twice the mass of our Sun and of late spectral type K, with an age nearly twice that of its so-called twin(724 million years).- or should it be triplets?
What blessed illusions the stars rain down upon us!
To be continued…………………………………..