*** New testimonies recently added to the end of the article.
For sheer brute force light gathering ability, Newtonian reflectors rate a best buy. No other type of telescope will give you as large an aperture for the money……For the sake of discussion, I have divided Newtonians into two groups based on focal ratio. Those with focal ratios less than f/6 have very deeply curved mirrors, and so are referred to here as ‘deep dish’ Newtonians. Reflectors with focal ratios of f/6 and greater will be called ‘shallow dish’ telescopes.
Pardon my bias, but shallow dish reflectors are my favorite type of telescope. They are capable of delivering clear views of the Moon, the Sun and the other members of the solar system, as well as thousands of deep sky objects. Shallow dish reflectors with apertures between 3 inches(80mm) and 8 inches(203mm) are usually small enough to be moved from home to observing site and quickly set up with little trouble………..Most experienced amateurs agree that shallow dish reflectors are tough to beat. In fact, an optimised Newtonian reflector can deliver views of the Moon and the planets that eclipse those through a catadioptric telescope and compare favorably with a refractor of similar size, but at a fraction of the refractor’s cost. Although the commercial telescope market now offers a wide variety of superb refractors, it has yet to embrace the long focus reflector fully.
From Star Ware, 4th Edition ( 2007), by Philip S. Harrington pp 32−33.
To savor stargazing we need to strike a balance between the time, energy, and expense devoted to this activity and what we channel into other necessary human tasks. A contented evening of stargazing comes with this balance. ‘In medio stat virtus’, or, as this Latin rendition of Aristotle’s maxim has been translated into English, “All things in moderation.’
Otto Rushe Piechowski
Sky & Telescope February 1993, pp 5
The trend towards larger and larger reflectors is indeed exciting, and I can understand the need to keep them short focus( typically f/4 to f/5). But why are so many small ones made with these focal ratios? Such telescopes bring out the worst in the Newtonian design. The 6 inch f/8s and 8 inch f/7s common many years ago, were much better and more versatile reflectors than many commercially available today.
Sky & Telescope, November 1993 pp 4.
Newtonian reflecting telescopes are great telescopes for observing Jupiter.
John W. McAnally, from Jupiter and How to Observe It, pp 152.
Indeed a high quality Newtonian reflector is a very powerful instrument, fully capable of superb performance in viewing the planets when the optics are kept clean and properly aligned. They have been amng the favorite instruments of serious planetary observers for many decades.
Julius L. Benton, Jr. from Saturn and How to Observe It, pp 57.
Newtonian reflector telescopes, apart from their complete freedom from chromatic aberration, can be made with much shorter focal ratios than refractors, usually between f/6 and f/8 so that even an 8 inch reflector is portable and easily affordable by most amateurs. An 8 inch refractor would be financially out of the question for the vast majority of amateurs and would need permanent housing in a large observatory. As a choice for planetary observation, then, there is a lot to be said for the Newtonian reflector in the 6 to 10 inch aperture range.
Fred W. Price, from The Planet Observer’s Handbook 2nd Edition, pp 41.
It is true that such reflectors are considerably less expensive than are refractors of the same size. This does not mean that they are not as good; in fact, Newtonian reflectors are more widely used by more experienced observers than any other type.
David H. Levy, from Guide to the Night Sky, pp 61
The simplest, cheapest and overall the most efficient design you could choose to use as a richfield telescope is the Newtonian reflector. As ever, an aperture of 100 to 200mm and a focal ratio of f/4 to f/6 is most appropriate.
Nick James & Gerald North, from Observing Comets, pp 57.
It is not proposed to enter upon the controversial topic of reflectors versus refractors. If does not grudge the extra attention to keep a reflector in perfect adjustment, its performance in revealing planetary detail will equal that of a refractor of the same aperture, particularly if it is mounted with an open, lattice work tube, when a further improvement may be derived from the employment of an electric fan to keep the column of air above the mirror well mixed.Moreover it has practically negligible chromatic aberration, whereas colour estimates made with a refractor are exceedingly unreliable.
Bertrand Peek, from The Planet Jupiter;The Observers Handbook, pp 37.
What is “over-expensive”? It depends on your point of view. A 106mm Takahashi flat field quadruplet refractor can be had, without mount, for only a little more than I paid for a high-end 12.5″ dobsonian Newtonian with state-of-the-art optics. If astro-imaging is your forte, the Tak will be the better choice. Don’t forget a high-end mount to go with it. For visual, though? Get real. The Tak will be severely limited–a well-machined, and beautifully-performing SMALL scope that can’t see much. If you buy your scopes for visual use, the Tak isn’t just over-expensive, it’s ridiculous. If you buy your scopes for photography, though, that Tak is an incredible choice.
Don Pensack from post no. 235 in an online a discussion on Why is Takahashi Overly Expensive?
Apochomats are expensive, particularly in the larger (repeated word ‘Larger’ omitted) apertures. Object the commonly available designs, reflectors are free of chromatic aberration since mirrors reflect all the colors identically. This means that a good quality reflector with a large aperture can be free of false color and yet provide the resolution and fine scale contrast while still being affordable. These Scopes have issues of their own..
Jon Isaac, from post no. 14 in an online discussion entitled, Can An Apochromatic Refractor Use More Powerful Eyepieces than an Achromatic Refractor Of The Same Size?
So What telescope Should I Spend with My Money On?
All in all, if you can afford it, and if you have the room to house it permanently in some sort of observatory (perhaps a run off shed), I would say go for a Newtonian reflector of 10 to 14 inches (254 to 356mm) aperture and as large a focal ratio as you can reasonably accommodate……..If you can’t afford a 10 inch then go for a smaller Newtonian reflector. Remember this type of telescope is the cheapest of any but please do not compromise on quality for the sake of size. My second choice for an instrument intended for visual observation of the Moon would be a refractor of at least 5 inches (127mm) aperture…
Gerald North, from Observing the Moon; the Modern Observer’s Guide (2007), pp 52
A first-rate 130-mm Newtonian is roughly equivalent to a first-rate 102-mm refractor for planetary observing, but superior to the refractor for all other purposes.
Tony Flanders, former Associate Editor, Sky & Telescope, in an online discussion ( post no. 1837) of the Astronomers Without Borders One Sky Newtonian.
The Newtonian reflector is a popular choice. Money wise, they are cost effective, and most importantly, you can obtain a large aperture telescope for a reasonable sum of money…..It is true the Newtonians can come with long tubes if a longer focal length and high focal ratio is required…..Although you will hear it said high focal lengths and ratios( example f/7 etc) are desirable for planetary work, telescopes with a focal ratio of f/5 can be very satisfactory.
Paul Abel, BBC Sky at Night Presenter, from his book, Visual Lunar and Planetary Astronomy (2013), pp 14/5.
The best view of Jupiter I ever had was at Peach State with a 12.5″ Portaball on an equatorial platform at 567x (10/10/2010). There was so much detail I tried to find a larger scope in use (no luck, alas). We could see albedo features on Ganymede and Callisto. Amazing what you can see on a night of exceptional seeing. Even when the seeing is not at its best, I find there are often times on any night when a larger scope has an advantage.
Alan French, from an online discussion (post no.14) entitled Large Telescopes and Jupiter.
Guan Sheng Optical (GSO) uses high-volume, state-of-the-art, high quality manufacturing and test lines. GSO guarantees diffraction limited performance, but their mirrors typically have a mirror surface quality of 1/16 wave RMS at least, and often better. This very smooth mirror surface results in excellent optical performance with practically no light scatter, while Antares Optics secondary mirrors are 1/15 P-V or better and come Zygo tested;
Rob Teeter, founder of Teeter’stelescopes.com
Amateur astronomers and telescope makers have debated from time immemorial the advantages and disadvantages of different telescope designs. In particular, mountains of hard copy and electronic articles are available on the merits of refracting and reflecting telescopes, more recently, apochromatic refractors vs. Newtonian reflectors. This debate has become rather rancorous (Newtonian telescopes as APO “killers” comes to mind.) and unscientific, to say the least. And when all is said and done, in a discourse without loaded words and acrimony, a discussion devolves to one concerning perfect optics. And isn’t this what we all want or wish we had?
From Ed Turco’s online article: The Definitive Newtonian Reflector.
Many people shy away from Newtonians because they have exposed optics that get damp and deteriorate. In this respect a good closed tube Newtonian wins hands down over an open tube one, as the tube keeps dew at bay. For the best planetary resolution, a telescope must, must, must must be precisely collimated!!! Also, the optics should be able to cool down quickly by fan cooling. Mirrors thicker than 40mm have serious cooldown problems unless fan cooling is employed. My 254mm f/6.3 Orion Optics Newtonian (plus mirror fan)is the best planetary telescope I have ever used. Some planetary observers line their tubes with cork too, to reduce currents. Many good planetary telescopes are comprehensively ruined by being in a huge unventillated dome with a narrow slit, a concrete floor and a metal dome.
Martin Mobberley, Author, from his webpage: Telescopes.
See also his review of the same instrument here.
Much has been written on the subject of the central obstruction and its impact on fine planetary detail. It remains a hot-button topic in on-line forums, and yet, despite the intensity of the debate, obstruction effects are well understood and fairly simple to quantify. The issue was most elegantly summarized by William Zmek in the July 1993 issue of Sky & Telescope magazine. Zmek’s rule of thumb states that if you subtract the diameter of the obstruction from the objective, you have the equivalent unobstructed instrument when it comes to contrast resolution. In other words, an 8-inch reflector with a 1.5-inch obstruction has the potential to resolve the same low-contrast planetary detail as an unobstructed 6.5-inch scope.
Gary Seronik, former Sky & Telescope Contributing Editor and Author, from his personal website.
I have the 12″ Orion as well (Truss, but the same thing otherwise). I have seen two other instances where optical quality on this model was excellent, and my own has perhaps the best mirror I have seen in a mass market dob.Star test with 3% obstruction shows an identical secondary shadow breakout, and the mirror had no zones or turned edge, and the smoothness was quite good. In other words, by anyone’s measure, the mirror in my own sample is a really fine mirror. If yours is in the same category for quality, be prepared for some awesome planetary views. The 12″ easily put up better planetary views than my 6″ Astro-Physics Apo and my C14. Views with 31mm Nagler and MPCC Coma Corrector are wonderful (I use the MPCC because it is 1x and while maybe not quite as sharp as the Paracorr, that 1x is important when trying to get the largest field possible out of today’s very expensive wide field eyepieces. I had fantastic views with my 12″ and it is my favorite larger aperture telescope ever. It does everything with excellence.
Ed Moreno, from an online thread entitled, First Light with my XT12G.
I tested the scope over a four week period, and found the optics to be very good, to excellent. I star tested the scope extensively, and found the mirror to be extremely smooth, with the slightest under correction.. I couldn’t put a figure on it, GS advertise 1/12 wave. Planetary images were rock hard. I tested the scope against my friend’s 12.5 Inch premium Dobsonian, which sports a “Swayze” mirror, and we couldn’t split the images over four different nights. On one particular night of excellent seeing, I had the magnification up to 500x, without any image breakdown.Our local club Telescope guy ran a series of tests on the optics, the main one being a Double pass Ronchi test, against a certified optical flat. He informed me the mirror was very well corrected, and very smooth. He didn’t believe the price I paid for the entire scope.
In summary, this scope has been a huge surprise. My experiences with “light Buckets” previously were not great. My intention was to use this scope for deep sky observation only, as I already have a Zambuto equipped premium scope for Planetary work, but it’s a lot more than that. Since purchasing my scope, I have looked through fourteen of these instruments at our club nights, and the images in all of them are almost identical. Guan Sheng seem to be producing a great mass-produced scope.
Astronomical Society of Victoria Inc
From a review of the Guan Sheng 12″ f/5 Dob (essentially identical to the author’s instrument pictured above). Source here.
I purchased a 15” Obsession from owner David Kriege on January 12, 2007 and took delivery in the first week of March of the same year. Since that time it has been my principle telescope for visual use. For comparison, I have owned two Takahashis (FS-102 and TOA 130), three Televues (TV85; NP127; TV85 again), a WO 10th anniversary 80mm, an 8” Celestron SC with Starbright coatings and a 6” Orion dobsonian.Despite the demonstrated affinity I have for apochromatic refractors, I had been to enough star parties to learn that aperture ultimately wins…………Those interested in purchasing a larger dobsonian may wonder what you see in a 15” scope. Having compared views with everything from 60mm refractors to a 30” dobsonian, I can honestly say “more than enough to keep you busy for a long, long time”. Globular clusters really seem to take life at about 12” and galaxies are already more than nondescript smudges by 15”. Of course local conditions make a huge difference. I have had nights with a 5” refractor that gave the 15” a run for its money. I have been at star parties looking at a galaxy in the 15”, then wandered next door to a 24” expecting to be utterly blown away by the difference and then been surprised by how little there was. That said, on any given night, the 15” tends to beat the socks off my small refractor nearly every night across the board, from planets to wisps.
From a review of the 15″ Obsession Dobsonian by Rene Gauge. See here for more details.
The Oldham optics on this Dobsonian are superb. A number of tests were carried out, the results of which are outlined below. The round airy discs of bright stars appear perfect. Faint stars are fine razor sharp points of light. On nights of good seeing I have been able to see faint diffraction rings around stars. Images snap into focus even at high power.
After extensive star testing, I could detect no major defects. There was no sign of any astigmatism, even close to focus. The test revealed near perfect correction and very smooth & high contrast optics. Given that the primary mirror is large and fast, and the star test is particularly sensitive, I consider these results to be very good. A particularly impressive aspect is the ability of the optics to handle very high powers. The results of the magnification roll-off test were excellent. First light revealed that the mirror could easily handle forty times per inch of aperture on planets. In good seeing conditions Saturn would reveal a high level of detail and remain sharp at magnifications in excess of 600X, and Jupiter showed no sign of image breakdown at 507X. Under no circumstances have I ever seen Jupiter soften at powers less than 450X. I have even enjoyed good views of the moon at 888X. I have also shared my experiences with a number of experts around the world who believe as I do that the optics are performing to a high specification.
Nick Koiza, from his review of a David Lukehurst 16″ f/4.4 Dobsonian detailed here.
Here’s what everyone wants to know. The primary mirror, as with all Zambuto-equipped Starmasters I’ve seen, is a jaw-dropper. Since quoting data on the mirror is often misleading and can cause flame wars, I’ve chosen to leave these out of this review. What I will say is that the Zambuto mirrors have an extremely smooth optical surface, with a near-perfect star test. Running through focus, the Fresnel rings are identical on both sides of focus and evenly illuminated. I can find no zones, no turned edge, and no astigmatism. There is perhaps a “slight” under-correction, however it’s often not even noticeable to me, which could indicate that I might have tested while the mirror was still slightly out of thermal equilibrium. If it is there, it’s very, very slight & I couldn’t begin to guess by what fraction of a wave.
However, that smooth surface correlates to what I believe to be the most important aspect of visual observing, and that is contrast. In a word – exceptional. The scope shows even the most subtle differences in illumination. There is definitely an emotional response with Carl’s mirrors, an underlying feeling that’s hard to describe, except to say sitting at the eyepiece is more like observing from space rather than the ground. The extremely fine details seen are amazing, and sometimes I seem to subconsciously pick up things that I don’t notice when looking through other instruments, only to go back to my scope & find that I wasn’t dreaming!
Jupiter usually shows 10 bands and massive amounts of detail within the belts & GRS, as well as the festoons & barges. And being able to see this kind of detail routinely at 400x, and many nights up to 600x is definitely like looking at a photograph. Polar regions & surface detail are visible on Io. Saturn shows the Crepe ring every night, as well as the Encke minima without fail.. Despite the short focal length it is a killer planetary scope. When Mars was last at opposition before the dust storms, picking out surface details was as easy as looking at our moon. In addition both polar caps were easily seen. Phobos & Deimos were also seen. On the planets I rarely use filters, so most of the views described above were natural.
No matter the conditions, the Trapezium easily breaks into 6 components, even at very low magnifications. The detail level seen in M42/43 is far better than any photo I’ve ever seen, from low-power views that show the entire nebula, to using a binoviewer at 500x on the Trapezium vicinity that reveals details in the nebula, which are reminiscent of the structure seen in cumulo-nimbus clouds.
With globular clusters, “resolved” takes on a new meaning & the scope provides “in your face” visual observing! Obviously M13 & Omega are completely resolved. One of my favorite globulars is M92 because of the super-dense core that seems to go on forever. One night I decided to push the scope to what our group likes to call “silly power” & view M92 at 700x. WOW – the core showed a tremendous amount of resolution, but again it’s so dense I couldn’t quite get it to go all the way. M13 at this power was like looking right through it to the other side. And I can’t forget the extra-galactic clusters, G1 & G2 in M31. G1 actually started show resolution at about 500x. Another extra-galactic object is NGC 604, the giant HII region in M33, about 2.5 MLY away. At 700x I can see much structure & filaments within the nebula. Seeing that in real time is spectacular.
Most galaxies within the local group show quite a bit of structure, knotting, & dust lanes. Those more distant objects do reveal detail well above being mere smudges. Many Virgo galaxies show spiraling. Every component of Stephan’s Quintet is always visible, and much easier to see than in many other scopes of similar aperture I’ve used. NGC 7331 is stunning. Closer neighbors like M51, M31, M33, M81/82, M104, NGC 4565 & NGC 891 take on photographic qualities in the eyepiece. I’ve been able to determine the rotational direction of a galaxy that NSOG stated was over 500 MLY distant. The scope is also quite capable of hunting the faint Abell planetary nebulae & galaxy clusters, and with an H-Beta filter, the Horsehead is a snap with direct vision. These are just a few of my experiences at the eyepiece. In short, once the mirror has reached thermal equilibrium, it’s like having a 14.5″ f/4.3 APO. Tight, pinpoint stars sharp across the FOV, and a nice “snap” to focus – there’s no mistaking it. The low f/ratio provides a nice wide field, at least for a scope of this size. I can get 1.4* with the 31 Nagler & using the Paracorr which boosts the focal length from 1584mm to 1822mm. (1.6* without it) Not a bad FOV for a 14.5″ mirror.
From a very happy and experienced owner of a 14.5″f/4.3 Starmaster Dobsonian. Details here.
Like every Sky-Watcher scope I’ve tested, this one arrived perfectly collimated out-of-the-box, and has held its collimation over the period I’ve been testing it. This speaks highly of the mechanical integrity of the scope, and alleviates the beginner’s greatest anxiety about Newtonians. No doubt the scope will require collimation at some point, but if it can make it to Canada to from China without losing collimation, it should be pretty stable.
I tested the telescope under the stars on four different nights, exploring a wide range of objects. Well, actually, one night and three mornings, as I was unable to resist the lure of using this scope on my old favourites, Jupiter and Saturn, currently in the predawn sky. I also spent time looking at the Moon, Mars, and Venus, favourite double stars like Epsilon Lyrae (split easily at 120x) and Rigel, and deep sky showpieces like the Ring Nebula and the Orion Nebula. All were well shown, as one would expect in a good quality 150mm scope. The supplied eyepieces, 25mm and 10mm “Super” modified achromats with 50° fields, performed quite well, yielding magnifications of 48x and 120x. This scope showed that it can handle much higher powers easily; I found myself using a 6mm eyepiece (200x) on the Moon and planets most of the time. Fans of deep sky objects will probably want to add a 2″ eyepiece to take in the wide field of view this scope is capable of.
As Terry Dickinson says in NightWatch, “There may not be a perfect telescope for the beginner, but the closest thing to it is the 6-inch Dobsonian-mounted Newtonian reflector.” The Sky-Watcher 150mm is an excellent example of this breed, at a very attractive price. My wife and I usually donate a telescope to our favourite charity to auction off each year, and this year this scope is our choice. Highly recommended!
I put together one of his 6″ f8 telescope kits with the help of my kids. It’s still one of my favorite scopes. These days, I lend it to people who have shown an interest in astronomy, but can’t afford a telescope.
Barry Fernelius, from this online thread discussing Stargazer Steve’s kit ‘scopes.
Changing technologies have meant that amateur telescope making has largely been replaced by the purchase of accessible high quality commercially produced instruments, but the Western world’s passion for the night sky is as strong as ever, and long may it continue.
Dr. Allan Chapman, from an essay entitled: The First Astronomical Societies, Astronomy Now, January 2018, pp 49.
Optical quality matters, but these days it’s usually not the main problem. Most of the commercial mirrors I’ve evaluated in the past 10 years have been pretty good — a few have even been excellent. That’s not to say there aren’t duds out there, but if your telescope isn’t performing, the items that top this list are more likely to be the reason.
Gary Seronik, from an online article entitled: Five Reflector Performance Killers.
In this department of astronomy, the names of Herschel, South, Struve, Dawes, Dembowski, Burnham, and others are honourably associated and it is notable that refracting-telescopes have accomplished nearly the whole of the work. But reflectors are little less capable, though their powers seem to have been rarely employed in this field. Mr. Tarrant has lately secured a large number of accurate measures with a 10-inch reflector by Calver, and if care is taken to secure correct adjustment of the mirrors, there is no reason why this form of instrument should not be nearly as effective as its rival.
W. F. Denning, from Telescopic Work for Starlight Evenings (1891), pp 290-291.
Since about a month this telescope is parked in my garage.
It is a Newtonian of 158mm aperture and a focus of 1240mm.The primary and secondary mirrors were made by David Hinds of UK.The telescope was home-made by my friend Tavi aka Erwin.Because he have other commitments, I was offered to give it a ride. I used the oculars seen in the second picture, from left to right: HM 6mm, Galilei – 50 mm, Galilei – 9mm , Baader Classic 6mm Ortho. This are the double.multiple stars observed on 23rd of December. All stars were split except 52 Ori where I believe to see a black space between main star and companion but not 100% sure.I was very pleased to see very well E and F stars in Trapezium.Good telescope, excellent optics, reliable mount……..I continued the testing on 26 of December when I made observations of 36 And, Delta Gem , Theta Aur and Eta Ori. All eas(i)ly split ,beautiful views……………..On 14 of January I targeted 7 Tauri double star. Unfortunately on the rare occasions when the stars were visible, the sky was hazy but still seeing was not better than 5 to 6 Pickering. Like with 52 Ori ,also at 7 Tau double star the Hind telescope showed at 248 x the two touching Airy discs but no black space bewteen them. I have high hopes in good seeing this telescope will split 0.7” double stars.
Mircea Pteancu from an online thread entitled: Double Stars in the Hind 158mm x 1240mm.
Visual report on the 12.5” f/6.5 Teeter Dob with Mike Lockwood mirror.
My eyepiece ‘fleet’ with the 12.5″:
31mm Nagler 67x
24 mm Explore Sci 86x
17.3mm Delos 119x
12mm Delos 172x
8mm Delos 258x
5mm Nagler 413x
6-3mm Nagler Zoom 344x to 688x
The first two nights (Tuesday and Wednesday) of observation were very foggy and absolutely dew-drenched – the most dew I have ever seen. Both nights the main mirror dewed up just after midnight – the joys of a thin 1.1” mirror which tracks ambient temperature very well, I suppose….
Along with the dew was some of the best atmospheric steadiness I have ever experienced. I would place the seeing at 9 to 9.5 (pickering) out of 10. With a 3mm eyepiece (688x) on a 4th mag star near the zenith, the full diffraction pattern was stable and almost unmoving. Unfortunately the transparency was mediocre and, towards midnight, increasingly poor….
The third night (Thursday) was very transparent and drier, with much more manageable dew but the seeing was extremely poor. The close pairs of Epsilon Lyrae were two touching fuzzballs (the night before you could have driven a HumVee through the blackness between…)
I looked at a bunch of double stars the first night… I used my Nagler 6mm – 3mm zoom which gives magnifications from 344x to 688x. Close pairs seen were:
STF 186: sep. 0.8”, mags 6.79/6.84
wide, dark sky split. The dark space was equal in width to the central discs of both components. very delicate first rings were present at all times…
A 1504: sep. 0.6”, mags 8.84/8.92
darkline split. Central discs ‘kissing’… first rings were pretty much too faint to see…
BU 525: sep. 0.5”, mags 7.45/7.47
very deep notch. a black or grey line seemed visible at times..
STF 346 AB sep.0.5” mags 6.19/6.21 This is triple star 52 Arietis. The ABxC pair is at 5” separation… Very nice to see three stars here. The AB pair was a deep notch, again with fleeting glimpses of a line between…
Dave Cotterell, Madoc, Ontario, from an online thread entitled: 12.5″ f/6.5 Teeter Dob with Lockwood Glass.
This report details my visual and photographic observations of some sub-arcsecond double stars that have been the subject of a few CN threads the past few months. This document is necessarily heavy on technical details to support those who may wish to independently evaluate the results.
Visual observations were made with a 15-inch f/4.5 Dobsonian reflector setting atop an equatorial platform. All observations were made between September 26th and October 26th of this year with a Paracorr Type I lens (setting no. 1) in the optical train. In all cases, Pentax lenses were used to achieve the following magnifications: ‘low’ (5XW; 398x), ‘moderate’ (3.5XW; 569x), and ‘high’ (2.5XO; 798x).
Imaging was accomplished using an ASI 178MC cooled camera [AVI files; mono mode] in an optical train consisting of a Paracorr Type I lens (setting no. 5) and a 5x Powermate. The plate scale for imaging was previously determined to be 0.0553 +/- 0.001 “/pixel using calibration stars (n = 10) and 0.0553 +/- 0.002 “/pixel using a diffraction grating with monochromatic red light (n = 8). Sharpcap 2.8 was used as the image capture software. Fine focus was achieved using a Bhatinov mask [All-Pro, Spike-a brand] modified to fit over the Obsession UTA. Separation values were determined using REDUC. Images were stacked and processed using Registax with final presentation formatting in Gimp.
Bu 720, 72 Pegasi
magnitudes: 5.7, 6.1
position angle: 105 degrees
separation: 0.575” (orbital elements estimate); 0.505” (last precise measure; 2015)
The separation data are not in good agreement for this object. This is, therefore, a good candidate for quantitative scrutiny.
At 398x the object vacillated on the border between elongated and just resolved to two golden-orange disks of similar magnitude in the correct position angle; 569x proved sufficient to show the stars as different magnitude and clearly resolved (but not yet split); a final increase in magnitude to 798x showed the pair as split, again with a golden-orange color and a small difference in magnitude. The ease of resolution at modest magnification led me to think the larger separation value [0.575”] was more accurate for Bu 720.
Bu 720 was easily imaged using an exposure of 10 ms [gain = 320]. Four movies were made and separation was measured by three methods using REDUC: cross correlation of the top 5% of frames using S4 filter; simple measure of a Registax composite; and simple measure of a composite generated in REDUC. There was good agreement across these methods, giving a measured separation of 0.61”.
STT 20AB, 66 Piscium
magnitudes: 6.1, 7.2
position angle: 176 degrees
separation: 0.598” (orbital elements estimate); 0.59” (last precise measure; 2015)
Good agreement between WDS listed separation values. Should be able to split at moderate magnification.
Low magnification (398x) shows two white stars that are clearly resolved and are oriented in the position angle as stated in the WDS. Moderate magnification (569x) shows that the components possess dissimilar magnitudes; the pair was barely split about 20% of the time at this power.
STT 20AB was imaged using an exposure of 12 ms [gain = 400]. Four movies were made and separation was measured by two methods using REDUC: simple measure of a Registax composite; and simple measure of a composite generated in REDUC. There was good agreement across these methods, giving a measured separation of 0.59”. REDUC Correlation methods were not useful with this target for producing separation values because of the faintness of the secondary.
16 Vulpeculae, STT 395
magnitudes: 5.8, 6.2
position angle: 127 degrees
separation: 0.849” (orbital elements estimate); 0.81” (last precise measure; 2015)
This target possesses a wide discrepancy between WDS values and was discussed at some length in a prior CN thread.
This object was observed as split using an 8-inch reflector at 340x (3.5XW lens).
16 VUL was imaged using an exposure of 14.5 ms [gain = 450]. Four movies were made and separation was measured by three methods using REDUC: auto correlation of the top 5% of frames using S4 filter; stacked REDUC reductions; and simple measure of a composite generated in REDUC. There was good agreement across these methods, giving a measured separation of 0.771 +/- 0.006”. Previous REDUC autocorrelation measurements of this system using a 2x Powermate [plate scale = 0.143 “/pixel] gave a measure of 0.78 +/- 0.02”.
Mark McPhee, Austin, Texas, from an online thread entitled: Examination of Some Sub-Arcsecond Doubles: Bu 720, STT 495, Bu172AB, STT 20AB, and 16 VUL
Currently, my only objections to the short f/ratios becoming common are that the depth of focus is very short, making focus variability in mediocre seeing a bit more of a problem than in longer f/ratios, and that most eyepieces don’t perform as well at the edges at f/3 as they do at f/5, even when both are Paracorred with the latest Paracorr II at the correct setting. But, that being said, I would still unhesitatingly choose a fast f/ratio at the really large sizes of scope simply because it’s easier and safer to stand on the 3rd step of a step ladder than it is to stand on the tenth (!), and I’ve done that in a 36″ f/5.
Along the way of large scope progress have come better cells, thinner mirrors, better fans, and better collimation tools. Put those all together, and the performance level of the large scopes seems now to be only limited to the mirror qualities, and there are makers of large mirrors now who put the same quality into their mirrors as some of the better makers who stop with much smaller sizes.
I truly wish many of you had seen the poor quality large scopes over the years that I have seen. If you had, you’d realize how we truly live in the Golden Age of Astronomy right now.
I thought I wanted a 140 class APO. The image and fantasy of it has been kicking around in my mind for most of the year. They’re such nice looking telescopes – what a telescope is supposed to look like. At a major star party a few weeks ago, I found a beautiful 140 – a very well-known top quality model mounted atop a big G11 and I asked the owner if he would please show me M15 in it. He was proud to do so and we looked. He raved and I was silent. I thanked him and walked back to my premium 16″ Dob. Looked at M15 in the 16 and raved to myself saying I’m so glad I have the 16. For the same amount of setup and money, what a difference!
Ps. Peter is the proud owner of a couple of large premium Dobs and an Astrophysics 175 EDF apochromatic refractor.
yea sometimes (like this evening) I ask myself too: “why you silly id… buy all this expensive apo stuff???”
Cloudy for the whole day – this evening reported to be one of the most interesting of the year – Io & Europa before Jupiter – together with their shadows and crowned by the GRS. Before 1,5h I saw a break in the clouds and to be fast I just grabed my 8″ GSO Dob and took it out. After 30min cooling another break off – I could see so much detail in the bands, GRS shining in a bright red, both shadows, Europa just beginning to leave the planets disc and – man – I could swear to see a round structure in the band that could have been Io… – best experience for a looong time!
So go get a 8″ f6 Dob – Houston out
Donadani, Germany, from an online thread entitled; How much increase in aperture to see a difference?
Hello Peter [Natscher],
Hope you are well.
An 8 inch Portaball with a Zambuto mirror on a tracking platform is going to show you much more than a 130mm telescope, even a Starfire 130EDF. Both of these will be sit down and observe telescopes. If you were not going to get a tracking platform, I would go the refractor route. You will want tracking for dedicated planetary or lunar observing. Shoot, you could roll the dice and get a Sky-Watcher 8″ f/6 collapsible Go-To dobsonian. I have the non motorized version and it has a great mirror, however, your mileage may vary on the chinese mirrors.
Tony M, from an online thread entitled: 5″ Refractor or 8″ Newtonian for Lunar/Planetary Observing.
I would take a high-quality 8″ f/6 on a GEM over a 5″ refractor. The GEM will negate all the disadvantages of the Dob. My old Meade 826 easily gives me a sharp, detailed Mars at 400x (conditions willing). I wouldn’t trade it for any 5″ scope ever made.
Rick Woods, from an online thread entitled; 5″ Refractor or 8″ Newtonian for Lunar/Planetary Observing.
I may be too late to add my .02, but it should be valuable.
I have owned a AP130EDF and the GT model. I now own an 8″ f/5.5 Portaball.
My conclusion: The Portaball rips the APs to shreds. A perfect 8″ mirror over a perfect 5″ lens…no comparison, obviously assuming collimation and thermal equilibrium. Especially since the Portaballs are constructed with fans and other ergonomics to help with the thermal adjustment. And I’m solely talking about visual planetary, since that is almost exclusively what I do.
Markab, Kansas City, from an online thread entitled: 5″ Refractor or 8″ Newtonian for Lunar/Planetary Observing.
One should never lean too heavily on sketchers. Although the vast majority are genuine, some go to an imaging website, study a particular image, and fake a sketch. In this way, they can make a 4 inch peashooter telescope look better than a Hubble image. I’d put more faith in the unlying eye of a CCD camera than any sketch, however elaborate.
A major reason refractors give images with higher overall contrast than reflectors is that objective lenses may scatter only approximately 2% of the light passing through them. This is why I believe that the high refelectivity coatings that are now applied to many astronomical mirror surfaces are so important. With 95% reflectivity, not only will they give somewhat brighter images but they will also greatly reduce the amount of scattered light, so improving the overall contrast. A high reflectivity coating is well worth having even at an additional cost; not only will the telescope perform better but a second advantage is that the mirror surface allows far less moisture to penentrate and is likely to last perhaps 25 years before it has to be recoated. I have a 10 year old Newtonian whose mirror was one of the first to be given a high refelctivity coating and it still looks like new………The overall design of the telescope will affect the overall contrast as well. It is impossible to beat a well designed refractor, but Newtonian telescopes, where one observes across the tube assembly to the far wall, are almost as good.
Ian Morison, from An Amateur’s Guide to Observing and Imaging the Heavens (2014) pp 10.
A Newtonian for All Round Use
A very good compromise in designing a 200mm Newtonian is to use a focal ratio of f/6, and many such telescopes are sold with this basic specification. The focal length will thus be 1200mm, and the field of view when a low power, wide field, 2 inch eyepiece is used will be approximately 2 degrees. The secondary mirror willprobably be approximately 50mm in diameter, and this would give a percentage of obstruction of 25% and provide full illumination over the central 25mm diameter region of up to 46mm diameter field of view. This is a good compromise, but some manufacturers, such as Orion Optics in the UK allow the purchaser to choose other secondary diameters should he or she wish to optimise the telescope towards planetary (approximately 36mm) or widefield imaging (approximately 60mm). One could even purchase two flats for use depending on the type of observations planned for a given night!
Ian Morison, from An Amateur’s Guide to Observing and Imaging the Heavens (2014) pp 64.
Yes, I have active cooling for my 10″ Dob. For that scope, a fan in a baffle below the primary works fine. I have an EdgeHD 8″, a SW120ED and a 10″ solid tube Dob, and I know how Jupiter looks in all three. No 7″ APO in the stable, but aperture does count for something. Some of my best views of Jupiter have been through the 10″ Dob during early morning. All of my best views of Jupiter have been through the 10″!
Sarkikos, from an online review of the Celestron EdgeHD 8 inch SCT.
Making a good 8 inch Newtonian by Toshimi Taki (Japan).
I think I can speak with at least a little credibility on this subject, having owned numerous large refractors:
One of only two Christen 6″ f/15 folded Triplets
8″ Alvan Clark
and having used several other premium 8″, 10″ and 12″ refractors.
As a recovering “refractor-holic” I still crave their look, fit and finish. And inch-for-inch they can’t be beat. But an 8″ or larger refractor w/mount is a true BEAST to own unless you can leave it permanently mounted. Topping it off there’s that little thing called “COST”!
Once we started having master mirror makers like Carl Zambuto et.al. turning out mirrors that were simply without compromise, optically – the paradigm shifted!
A premium 12.5″ reflector today will simply blow away that beautiful old 8″ Clark. My present 14.5″ Ed Stevens mirror produces planetary images that are superior to anything I ever saw in a 10″ Zeiss triplet and pretty darn close to the 12″! And don’t even get me started on comparisons with my 28″ Starstructure w/Steve Kennedy mirror! This scope is fully driven and features GOTO, yet I can set it up, take it down and transport it (easily) all by myself. Try to picture what a 20″ refractor would look like and cost…that’s about what it would take to begin to match the performance!
Would I love to have a giant TMB set up in a dome behind my house? Sure! But not for ‘performance’ reasons.
Mike Harvey (Florida), from an online thread entitled: Refractor Versus Reflectors.
My 6″ refractor [AP 155] will show the arms of M51 from a dark site, but fairly subtly. It’s far behind what my 10″ Dob can do in that area.The inability of the refractor to show much spiral detail in galaxies is probably its greatest drawback as a deep sky instrument.
Joe Bergeron, (Upstate New York, USA), from an online thread entitled: Refractor Versus Reflectors.
My advice to everyone wanting better planetary views is is to always spend money on a better instrument, or make their instrument better than it is. An 8″ f/6 reflector with a high quality mirror is one of the best planetary scopes money can buy. Period. Don’t be duped into thinking a 6″ MCT is going to be better. Physics simply do[es]n’t permit it.
Ed Moreno, from an online thread entitled:8 inch f/6 Dob versus 6 inch Orion Mak on the Moon and Planets.
I’ve tried a single curved spider in my 8 f7.6, but went back to the straight 4 vane after a year. Didn’t notice even a tiny hint of more fine detail on Jupiter with the curved vane.
Planet Earth, from an online thread entitled: Curved Spider Vanes?
The idea of curved-vane spiders isn’t new — the concept has been around for a long time and several designs were detailed in the May 1985 issue (page 458) of S&T. For telescopes up to 12-inch aperture, a curved spider can be a good alternative to traditional 3- or 4-vane spiders. With larger scopes, the diagonal mirror typically becomes big and heavy enough that the greater rigidity offered by conventional spiders or more robust curved ones may be required. I’ve successfully used the design described here in numerous telescopes, including my 12¾-inch. My single-curve spider has the added benefit of being simpler than the ones in the 1985 article, and therefore easier to build.
Gary Seronik, from his online article: How to Build a Curved Vane Seconday Mirror Holder.
This is essentially an aesthetic issue. If you don’t like spikes, then go ahead and get a curved vane spider. It does eliminate the spikes. You will see an even glow around bright objects like Jupiter or Venus, and nothing around everything else……..If the spikes don’t bother you, then stick with a straight vane.
Jarad, from an online thread entitled: Curved Spider Vanes?
I have put a 6″ APO up against a mass market 8″ f/6 reflector and I can tell you that the 6″ APO overall is a better performer. It is sharper everywhere in the field, had better planetary contrast, and came SURPRISINLY close in terms of deep sky (Globular and Galaxy) performance.
But this didn’t have much to do with the fact that it was a refractor vs a reflector, but rather more to do with the fact that is is a virtually PERFECT refractor up against a telescope with optics that were only “Fairly good” optically.
But.. IF you were to put a TOP QUALITY mirror in your scope, along with the highest quality diagonal you could find, you would find that on axis, it would indeed take refractor very close in size to yours to give a better visual image at the center of the field.
Ed Moreno, from an online thread entitled: Refractor Equivalent to a 8″ Reflector.
A good 7.1″ refractor is very close to a good 8″ reflector on M13. For planetary resolution most of the time the 7.1″ refractor beats the good 8″ reflector. But, they can be very close on a good night.
Rich N (San Francisco Bay Area), from an online thread entitled: Refractor Equivalent to a 8″ Reflector.
As I mentioned earlier in this thread my experience is that a 7.1″ refractor is very close to an 8″ Newt.
I’ve had my AP 180EDT f/9 APO side by side with a friend’s well made 8″ Newt a number of times. My refractor is more consistant in giving high contrast, high resolution images but on the right night that Newt can give some fine planetary images. For deep sky the views are very similar.
Rich N(San Francisco Bay Area), from an online thread entitled:Refractor Equivalent to a 8″ Reflector.
I’m not talking about local seeing from night to night. I’m suggesting that if you set up a high end APO and a high end Newt of roughly the same size (maybe a 180mm APO and 8″ Newt) side by side over several nights, the APO (refractor) will more often show better high res, high contrast, planetary detail.
Rich N(San Francisco Bay Area), from an online thread entitled:Refractor Equivalent to a 8″ Reflector.
No, a well crafted 8″ reflector with a Spooner f/7 mirror will totally outclass not only 5 or 6″ achros, but 5 or 6″ apos as well. And look at the original posters question again. He was wondering if an 80mm refractor would equal a 6″ reflector or a 100mm refractor would equal an 8″ reflector. No, and it’s not really close. And if you can tie your shoe you can collimate a reflector and clean the mirror once a year.
And my 6″ $250 Orion 6″ f/8 Dob has run totally neck and neck with my buddy’s Tak 102 on more than a few nights on the moon and planets. And it’s beaten the 4″ apo on some nights. Same result with a TV102 and a Vixen Fluorite 102. And it beats my TV85 and his Tak 78 100% of the time. Myths die hard.
I routinely compare 6″ APO to 7″ and 8″ Zambuto reflectors – see my sig for specifics. I am a dedicated planetary observer and really enjoy such comparisons.
Basically, I’ve found that the 8″ Z-mirror when cooled will be ever so slightly better then the 6″ APO. And the 6″ APO will edge out the 7″ reflector. The 6″ APO, an FS152, is a doublet and does not focus all colors to a common point as a matter of design. The blue is thrown way out of focus so the image has a slightly warmer look to it then that of the reflectors. I have often wondered if a triplet was compared to a the 8″ reflector how it would perform. Probably the same as the doublet as resolution is primarily a function of aperture.
The differences are quite minor in good seeing. But when the atmosphere is unsteady, I prefer the views in the FS152 over everything.
Peleuba(North of Baltimore, MD), from an online thread entitled: Refractor Equivalent to a 8″ Reflector.
I have a nice C6-R with a Chromacorr, and a nice 8″ f8 newt with a very fine Raycraft Primary, Protostar secondary, and flocked interior. I can’t recall offhand the size of the secondary, but it’s scaled for my 2″ EP’s, so it’e bigger than is optimal for planets.
Aestheticly, I find the refractor better, especially on evenings of dropping temps. I know the refractor has to cool too, but the views seem to be sharper sooner, and I never see tube currents.
The newt does reach deeper, though. But, I generally like to see sharper than deeper for the kinds of things I use the refractor for (planets and clusters). When depth is the concern, I opt for more aperture.
Under ideal conditions, I’m sure my 8″ newt will out-perform the refractor. But, conditions are rarely ideal, and so the edge goes to the refractor– tends towards better sharpness and better contrast due, I think, primarily to the lack of tube currents and cooling time.
Apples to Oranges, though.
Kerry R (Mid West Coast, Michigan), from an online thread entitled: Refractor Equivalent to an 8″ Reflector.
I will go toe to toe with any 7″ or 8″ APO with my 8″ F8 Newt and my Dan Joyce 8″ f/6.7 Newt. In the end I paid very litte for both Newts, and the 8″ APO owner has paid big time for the 8″ APO and it’s mount.
Had my share of 5″ to 7″ APO’s and they just dont cut it for such a high price. They do give that super fine snap to focus image, but my well built 8″ Newts can pretty much do the same thing and cost 50x less.
CHASLX200 (Tampa, Florida), from an online thread entitled; Refractor Equivalent to an 8″ Reflector.
8″ f/6. You’ll get a little better contrast with an unobstructed scope and imperceptibly brighter image because of light loss on a reflective surface. You won’t have coma on a refractive system, but you won’t have the huge amounts of CA with a Newt that you would have with an 8″ f/6 refractor.
Aperture, aperture, aperture. That’s what matters. A high quality, thermal controlled reflective system will give up very little to a similar size refractor.
Deep 13 (NE Ohio), from an online thread entitled: Refractor Equivalent to an 8″ Reflector.
Recognizing that everyone has their own opinions and preferences, here is my opinion and preference based upon 45 years of telescope ownership which by inventory would include something like about 40+ mounted telescopes and numerous guide scopes that would add about 15 or so more to the mix. I have had all types of scopes including both apo and achro refractors, maksutovs, schmidt-cass, newtonian reflectors (both equatorially mounted and dobsonian). While different telescopes are suited for different purposes, my overall preference is the refractor for a number of reasons, in particular the apo refractor of which I have owned 8 different apos. I also enjoy the classic long focal length achro refractor and have extensive use and ownership experience with Unitron refractors………………From my personal experience and in general for most applications my rule of thumb would be that a Newtonian would have to “out-aperture” a refractor by about 33% to be roughly equivalent for most applications. Accordingly the statement that a 6″ refractor is equivalent to an 8″ reflector is for the most part, pretty valid.
Barry Simon ( New Orleans, LA), from an online thread entitled; Refractor Equivalent to an 8″ Newtonian.
My guess is that a great 5 inch apo refractor would equal an average 8 inch mass produced mirror and it would take a great 6 to 7 inch refractor to equal a great 8 inch reflector. A generic 10 to 12 inch mirror will beat or equal any refractor under 8 inches. These guesses are based on real world observing at most objects. There are always exception.
Wade A. Johnson (North Central Iowa), from an online thread entitled; Refractor Equivalent to an 8″ Newtonian.
I have done the side-by-side during a couple of well attended starparties. My well collimated and optically very good C8 performed extremely similar to a very good Meade 6″ APO on Jup[i]ter on a night of exeptional seeing. The refractor edged it out with better contrast. No surprise. Compared to a home made 8″ Newtonian with a small 20% obstruction the images were almost impossible to tell apart.
So, my answer to the original question is: 6″ refractor.
I think we are finally well past the myth of a 4″ refractor being “sharper” or “showing more” than an 8″ reflector.
Contrailmaker, from an online thread entitled: Refractor Equivalent to an 8″ Reflector.
This old and tired conversation just seems to drag on and on, using the same old arguments that fly in the face of both common sense and physics. Drop it…let’s all agree that a 6″ Apo costing $7000 is a bit better than an 8″ F5.9 reflector costing less than $1000.
Which one would a sane person on a budget buy?
Covey32 (Georgia, USA), from an online thread entitled: Refractor Equivalent to an 8″ Reflector.
I would politely disagree to this. I looked through an excellent 5″ apo (my old Tak TOA-130S) and a very good 8″ Newt (8″ f/7) at Jupiter and Saturn. My Tak was soundly beaten by the views through the 8″ Newt.
Alvin Huey (Greater Sacramento) from an online thread entitled: Refractor Equivalent to an 8″ Reflector.
An 8″ mirror doesn’t have these thermal stability issues that are fundamental to larger apertures. Cool-down is relatively quick as long as you have a pyrex mirror. An 8″ plate glass mirror with a fan will also cool down quickly.
8″ f/8 newts (provided they have a solid/split tube design) can be staggeringly good planetary scopes. Wholly apart from the materials costs of refractor glass, you’re more likely to get a perfectly figured optic than you are with an apo. Refractors have more optical surfaces that have to be accurately figured (4 in a doublet, six in a triplet) whereas a newtonian only has one. At f/8, if using a low-profile focuser, the central obstruction is miniscule and the increase in contrast over a shorter focal length newt can be dramatic. Also, using a single-arc two-vane curved spider like a protostar can go a long way towards minimizing overall diffraction. Also at 8″ or less, the flexure inherent in that design is negligible enough not to affect performance.
Zamboni, from an online thread entitled: OPT 8″ f/9 Planet Pro Dobsonian.
The Astronomers Without Borders’ One Sky Newtonian; an affordable but good quality, ultraportable 130mm f/5 tabletop telescope.
We have 4 scopes that always see some use. A 8″ F8 Newt (Dob mount), a 111mm APO (actually, a lot of 4″ refractors), a 16″ SCT and a 17.5″ F4 Newt (dob). The 8″ has some of the best optics I have ever had the pleasure to use, a true one of a kind scope. Planets are fantastic through it. Actually, pretty much everything is. But, when I want to look at galaxy clusters or similar, the 17.5″ is the scope. When I want to study the details in planetary nebula or small single galaxies, I like the 16″ SCT. On exceptional nights, the 16 is great on the planets too but those nights are far and few between here in the Great Lakes State (only 1 really comes to mind in the last 10 years…).
Jason B, (Michigan, USA), from an online thread entitled: 1 inch Apo vs 12 inch SCT.
Under the stars, this telescope really shines now. It really is nearly the equal of my 10 inch f/6, a ‘scope I have been told by many who look through it, has Zambuto like quality. Planetary detail is excellent. Deep sky is just great. I find myself surprised over and over again by this telescope. The figure on that primary is just excellent. We did not touch what the original guys at Cave Optical did with the figure, we just recoated it. I reviewed this ‘scope on the Todd Gross astro equipment ratings site, and I’ll tell you now what I said then. If you like vintage ‘scopes and you don’t have one of these, try to find one. You won’t be disappointed!
Edward Conley, (North Branch, MI, USA), from an online review of a Classic 8″ f/7 Cave Astrola Newtonian.
FWIW Rolando [i.e. Roland Christen] said the best view he ever had of Saturn was through a 12.5″ Cave – 800x was no problem.
deSitter, from an online thread entitled: Cave Telescope Estimate of Worth.
Jupiter on the morning of October 8 2010 by Jason H ( Central Florida, USA); afocal footage from a Criterion RV 8 f/7 Newtonian reflector.
When I rece[i]ved my 6″ F/8 Criterion RV-6 I was amazed at the detail I could see on Jupiter. Since then I have heard many others say how well their RV-6 scopes performed. Why did these scopes seem to perform so well? How do they compare to “modern”: Newtonians like Zambuto mirrored scopes?
Jim Philips (South Carolina, USA), on an online thread entitled: Criterion RV-6 Dynascope.
Well I always like to have an excuse to repost a picture of my restored 1960 or 61 original RV6. Yes the optics are as good as everyone reports. I agree with what others have written that the 6 inch at f/8 is relatively forgiving and if well made performs excellently even with a spherical curvature. After seeing a neighbors RV6 outperform my Astro Physics 6 inch f/8 triplet,(early model), I sold the refractor and restored my RV6 to almost like new condition.
Bill Nielson (Florida, USA), on an online thread entitled: Criterion RV-6 Dynascope.
Went to my club Saturday nite and happened to set up right next to a gentlemen who was using a 5 inch Takahashi refractor. I was using my 8 inch Orion Intelliscope. We struck up a conversation and soon began swapping scopes on different targets. Now as some of you know, i got the Dob to tide me over while saving fro a premium APO. Well, to make a long story short, my lowly, mas produced mirror beat the state of the art fluorite lens on every single target, planets included. Interestingly, it wasn”t i who first acknowledged this, it was the guy who owned the Tak. He kept bringing his own ortho eyepieces over to my scope, and shaking his head. As a recovering CRF, this was very validating for me. I am really no longer seeing any advantage at all to ultra expensive refractors. Not to mention that, while stunningly beautiful, and well made to say the very least, his scope and mount combo is a boat. Mine was out and ready in under 5 minutes. In conclusion, I am no longer aspiring to get the 4 to 5 inch APO, rather my next upgrade will be a 12 inch newt, which, because of cost, can happen a lot sooner. Personally, at this point, I see refractors as excellent, rugged, grab and go travel scopes. I am quite happy to be in the reflector camp at the moment.
Aperture rules and a lot always depends on the seeing which is the great equalizer, but a well made Newt with a reasonably small secondary mirror can be a great planetary scope. The secondary mirror will always lower contrast compared to the unobstructed Apo, but the higher resolution of an 8” brings something to the view that the 5” telescope can’t.
Snart, from an online thread entitled 8 inch Newt vs 5 inch Apo.
I just got back from a weekend star party and pretty much had observed the same thing. My well collimated DOB showed more and better than anything that had less aperature. Since I cant afford anything in the APO category, it left me pretty pleased with my equipment…….. VERY encouraging. I guess my homework and the help supplied from CN has led me to the right stuff!
The hang up over reflector verses refractor seems to originate in the 1950’s-1960’s. Even Patrick Moore will say buy a three inch refractor or a six inch reflector.
However times and tech have changed. It just takes time for the astro community to accept this. I own a 14 inch reflector and I also own an 8 inch mak. I have also owned a five inch apo. The most used scope is the 14 inch reflector. I have been into astronomy for 30 years, I have been very active and I know my stuff.
Don’t forget if someone buys an apo for $2000 they want it to out do any other type of scope that costs a third less,their opinion will rely on the cost. It is human nature.
It just boggles my mind that a piece of equipment costing in the three hundred dollar range can outdo one costing in excess of 5000 with mount.
Being a newt guy, I’d agree that an 8″ reflector can beat a 5″ apo refractor. However, I would point out a few things: The newt may require more cooldown time, and it may be more affected by seeing conditions, tube currents, etc. The newt will show diffraction spikes around bright objects unless a curved spider is used, while the refractor will obviously not. The refractor may show a “cleaner” image, but not necessarily more detail. This is especially true if the newtonian has a large central obstruction, isn’t flocked, etc….The great thing about newtonians is that they’re easy to modify. A flocked, collimated, cooled down newt with a curved spider, nice focuser (being perfectly in focus is important on planets!), and good optics will be right on par with an apo refractor of the same aperture minus the secondary obstruction, IMO.
Erik, from an online thread entitled 8 inch Newt vs 5 inch Apo.
like i always show my students; a 6″ unobstructed, perfect optic is creamed in resolution by a 10″ 20% obstruction 1/10 wave newt:
http://www.astromart…?article_id=473 (thanks darren!)
this is why i always wonder when people say refractors are best on planets…..
like i always show my students; a 6″ unobstructed, perfect optic is creamed in resolution by a 10″ 20% obstruction 1/10 wave newt:
That’s fine, Dave but your skirting the issue. I’ve now been painted into the corner. Can you give the nod to a 6 inch
F/8 reflector against a 150mm Tak,AP,TMB,etc,?
if they both cost the same, i would take the 155mm AP.
if the 155mm AP and an 1/8 wave 8″ newt both cost the same, i would of course take the 8″ newt.
When I owned an 8″ Mag1 Portaball with a Zambuto mirror, I used to compare the views of the planets through my telescope with refractors. Over a two year period, there were a few refractors that came close to providing better views on a few exceptional nights, but I didn’t find a refractor that could compete head-to-head with my reflector. (The best refractor, the one that came the closest, was an AP 155, if I recall correctly.)
I now own a 12.5″ Mag1 Portaball (also with Zambuto mirror.) I’m still waiting for the night where the refractors demonstrate their clear superiority. I’m not holding my breath. Under crappy seeing conditions, I’ve seen the phenomena of a refractor providing what its owner called ‘a more aesthetically pleasing view.’ This is another way of saying when the seeing is bad, smaller aperture scopes don’t see the bad seeing as well as [a] large aperture scope. (In this type of condition, one can ‘stop down’ the larger scope and see the same sort of views that are seen by the refractor.)
When the seeing is good to excellent and when optical quality is excellent, aperture wins every single time. And dollar for dollar, high quality reflectors rule.
But don’t take my word for it. Check out Gary Seronik’s article “Four Infamous Telescope Myths” in the February 2002 issue of Sky and Telescope. You can also go to star parties and try a few experiments. Under good seeing conditions, take a look at the planetary views through a correctly collimated reflector equipped with a Zambuto, Royce, Swayze, Hall, etc. mirror. Then take a look at the views through a 6″ refractor that’s many times more expensive. I think that the results might surprise you.
Finally, consider this Mars image, made by Wes Higgins with a 14.5″ Starmaster. In the past, when the optics in most large reflectors were mediocre at best, I believe that high quality refractors provided the best views. Now, with high quality optics readily available in large reflectors, I believe the situation has changed.
Barry Fernelius, from an online thread entitled, Reflector versus refractor.
What more and more people are doing right now in France, is to buy those chinese 8″ or 10″ f/5 or f/6 Newtonians, play with them for some time, then have the primary mirror refigured to an exceptional quality for around €1,000 (US$ 1,250) with enhanced reflective coatings. They perhaps add a better focuser and tweak the spider a little bit. After that treatment on a 8″ reflector with 20% central obstruction, a 6″ APO can no longer match it for visual work.
Rhadamantys, from an online thread entitled, Reflector versus refractor.
At the risk of beating a dead horse, my experience is that an APO refractor delivers consistently a[e]sthetically pleasing results every time, with detail limited only by atmospheric conditions and aperture. A high-quality, well designed newt can also deliver [a]esthetically pleasing views, with detail limited only by atmospheric conditions and aperture. Everything else being equal, quality aperture wins, every time. Not surprising that (last time I checked anyway) Thomas Back’s personal scope for planetary viewing is….wait for it…. a 20″ Starmaster. Nuff said?
Gary in Ontario, from an online thread entitled, Reflector versus refractor.
A 130 mm F/5 with a decent mirror and a 2 inch focuser. No CA, much faster than the Mak or the refractor for EAA and very rugged.
I’ve owned several.. It’s scary sometimes how good they can be. I remember one night under dark skies.. I was doing the low power, wide field thing with my NP-101 and swapped it out for a 130 mm, F/5 Newtonian with the 31 mm Nagler and a paracorr. I wasn’t giving up much with the $200 scope.
Jon Isaac(San Diego, California), from an online thread entitled: 4″ refractor vs. 4″ Mak.
As John Browning was to argue in his ‘Plea for Reflectors’ in 1867, good silver-on-glass reflectors had tubes about half as long as those of refractors of similar aperture, they had a superior resolving power when used on dim double stars or planetary surfaces and often gave crisper star images, while unlike large aperture refractors, they were not ‘beyond the reach of all but wealthy persons’.
Allan Chapman, The Victorian Amateur Astronomer, pp 230, (1998).
James Francis Tennant, for example, had used a Browning mounted With 9 inch (silver–on–glass mirror) to observe the Indian eclipse of 1868, while in 1872 Joseph Norman Lockyer had one which produced ‘exquisite definition’. The With instrument in the Temple Observatory at Rugby School and one in a privately owned observatory in Sydney, Australia, were found superior to Clark and Merz refractors of similar aperture. By 1890, With’s mirrors were in use in Europe, Canada, Australia, Asia and elsewhere.
Allan Chapman, The Victorian Amateur Astronomer, pp 232–233, (1998).
I find that the ideal planetary telescope is the largest quality aperture that you will use frequently. It can be fast or slow, in terms of f/#, so long as the optics are good. Ideally the primary is not too thick so it can cool and be cooled in a reasonable time. Proper mirror support and achieving and holding collimation are also very important.
Mike Lockwood (Philo, Illinois), from an online thread entitled: Help me pick a larger planetary scope.
I think that the ideal set up would be a 10″ F/7 Newtonian reflector on a GEM.
Stephen Kennedy (California), from an online thread entitled:Help me pick a larger planetary scope.
My best planet views came from all of my Zambuto and OMI 11 to 18″ mirrors and all were F/5 or faster. On the smaller size mirrors i like slower speeds in the 10″ and smaller sizes.
There is no way a 4″ apo will destroy a larger Newt!! Simple laws of physics are at play here. My 6″ Newt with a 20% obstruction consistently shows more planetary detail than ANY of my 4′ Apos ever did!! My former Takahashi TSA102 never performed as well on the planets as my large dobsonians did. Aperture wins, every time! Small apos really shine in the portability department so they are eminently well suited to quick setup and teardown times.
I am just not a APO fan in sizes over 4″. 3 and 4″ APO’s are my fav all around small scopes. Once you get into the 5″ and bigger sizes cost become a problem for me and 7″ and bigger the mount needed becomes pricey and big. A bigger Newt is many times cheaper and does what i need it to do. No 7″ or 8″ APO would give me the image at 1100x+ like my 14.5″ and 15″ Zambuto and OMI optics have done time and time again.
Last year I was privately discussing splitting some close doubles with a fellow Cloudy Nights member on the east coast. He was using a 175mm apochromatic triplet refractor that cost $20,000. I was using a 10 inch (250mm) Dobsonian that I bought used on Astromart 15 years ago for $240. One double in particular I had split cleanly with my $240 scope which had eluded the expensive refractor. This was due to the greater resolving power of the larger aperture and the more stable atmosphere (better seeing) of my location.
I am not a bino viewer at all, and my particular vision doesn’t do binoculars, thru a telescope or even at the football field. But I do have personal experience comparing an Orion 120mm ED scope and a GSO 8″ newtonian on Saturn one night, probably some 11 years ago now. Hands down, the GSO (an old Meade LightBridge 8, back when they made them) beat the Orion 120mm ED scope on Saturn. The image was brighter and more detailed. I am certain a 10″ would have done even better, so if you think you’re a refractor guy now, a 10″ newt, should you figure out how to configure it, will convert you, for sure. The collimation and mechanics are the tricky things with these Chinese sourced newtonians, but I’m convinced the optics are actually pretty good. Not saying custom, American/European/Japanese mirrors aren’t better, but the standard Chinese mirror these days is really pretty good. Now the mechanicals associated with the scope are often not as good as the optics, so achieving the best views can be difficult to obtain, even tho the optics may, indeed, be quite good. My friend (who owned the 120mm ED) and myself were impressed with the mirror in the Meade LB8. I have a friend with an Orion Intelliscope 10″ and the views through it, at least on-axis cause he doesn’t own a coma corrector, are spectacular — Thor’s Helmet, Sculptor Galaxy, Jupiter, etc.
I have owned a 1/2 dozen garden variety XT6/XT8 Dobs over the last 25 years. None of them were anything special, but they were consistently OK. I also simultaneously owned a sensibly perfect 4” APO and a custom 8” Dob with Zambuto optics.
The 6”f8 Dob consistently gave me better views of all objects than the 4” APO. The 8”f6 Dob consistently gave better views of all objects than the 6”f8 Dob. The 2” difference wasn’t a “wow,” but it was obvious.
The custom 8” Zambuto equipped Dob gave marginally better views than the 8” Synta Dob in excellent seeing, but the difference in the views was much more subtle than the difference that comes with 2” of extra aperture, which is why I would expect a typical, garden variety 10” Dob would probably give better views of anything than a sensibly perfect 8” Dob and cost much less
For reference, a complete XT10 costs $600 and is available off the shelf. An 8” Zambuto mirror starts at $1,100 with an 11 month lead time. A Zambuto equipped 8” Teeter starts around $3,300 with a 4 month lead time.
gwlee (California), from an online thread entitled: Premium mirror versus Chinese mirror.
Beyond that, the main thing is to get out there and use it. I don’t really worry much about whether a premium 8 inch would out perform my GSO 10 inch because the 10 inch does a reasonable job of doing what I ask of it. I do know that I have been able to split double stars with it that are beyond the Dawes limit for an 8 inch. Some pretty awesome planetary views at 410x.. And deep space.
Jon Isaac (San Diego, California), from an online thread entitled; Premium mirror versus Chinese mirror.
I have enjoyed Sky Watchers scopes for 10 years now in almost every circumstance, under light polluted or super dark skies, under ugly or really good seeing, side by side to terrible scopes or world class (Astrophysics) refractors, close the newbies or really experienced observers. They have never disappointed me, when conditions allow, they deliver terrific planetary and deep skies images.
Javier (Buenos Aires, Argentina), from an online thread entitled: Premium mirror versus Chinese mirror.
I had a 120 mm Orion Eon for two years. This is a 120mm F/7.5 FPL-53 doublet and probably better optically than your 120mm Binocular Telescope. I recently sold it because my generic 10 inch GSO Dob was the better all around performer and not just by a little. The Dob was better on the planets, it splits doubles not even worth looking at in the refractor. Globulars, nebulae, galaxies, for deep sky it’s a break through experience.
Jon Isaac(San Diego, California) from an online thread entitled: 10″ Newtonian to upgrate an ED 120.
After having large aperture Newtonians and Refractors, I would say yes, it’s possible to make a Newtonian as good as a a Mid priced apo. My current(and final) scope, a 6″F8 newtonian provides refractor like images of the planets and double stars. Everything snaps into focus and looks as good as in my former 4 and 5 inch apos. At this point in my life, an arthritic back and knees prevent me from owning anything larger and I like the convenience of a dobsonian mounting. I’ve always said that if I could have only one scope, it would be a 6″f8 reflector. It’s an outstanding performer and an excellent compromise between aperture and focal length!!
Barbie, from an online thread entitled; How hard is it to make a reflector as good as mid-price ED or Apo refractor?
The advantage of a reflector is that it scales to a larger size much more affordably; at small sizes that advantage is much less. That is why you see small refractors and large reflectors. The notion that a 4-5″ reflector should be the same price as a 10-12″ reflector, though, is an unrealistic expectation. Next to a 12″ dob, a 127mm refractor looks like a kids toy… they are totally different leagues. Make no doubt about it, a 12″ premium dob will blow a 127mm refractor out of the water in every category except wide field views and ease of use.
dgoldb, from an online thread entitled: How hard is it to make a reflector as good as mid-price ED or Apo refractor?
As Danny shows, the real world can be tamed a little or a lot. Cooling and boundary layers, collimation, and a few other variables are within our ability to minimize. In the tropics the real world is, at times, almost “lab like” with very good seeing and modest temperature differentials. So, even though we cannot talk about performance in isolation, we have a measure of control over “real world” performance except for seeing mostly. We can give our ‘poor’ scopes a fighting chance to perform better than they are often assumed to perform…in the real world, of course.
Asbytec(Norme)(Pampanga, Philliippines), from an online thread entitled, Premium mirror versus Chinese mirror.
I agree with Norme, often performance is all about location, location, location! What works well in the south, or out west might not be the ideal scope for the NE or other locations. You have to tailor your scope to your location and observing goals/habits to get the best consistent experience. There is no such thing as the perfect scope for any location, observing style etc. If there was we would all have it.
Richard Whalen (Florida), from an online thread entitled, Premium mirror versus Chinese mirror.
I have a superb TEC200ED and equally superb (optically, mechanically and coolingly…did I just make up a word?) Parallax/Zambuto 11″ F 7 Newt. Other than image brightness and a slight warmth in the TEC’s color tone, there is little difference between them for solar system viewing. Sometimes I prefer the TEC, others the Newt. The only “glaring” difference is the Newt’s diffraction spikes, especially on Jupiter and Mars. But I’ve learned to live with the spikes and ignore them much like I can ignore CA in achromats ( if it’s not too severe anyway), however there are also solutions for that too.
For me, the key to really enjoying my newts has been great optics & great mechanical and cooling designs. I want my newts to behave like an excellent APO and I’ve found that it is easily done if I pay attention to the big three: optical quality, mechanical design & execution, and cooling design & execution. Everything else is “sauce for the goose” for me (however, I freely admit to being one of those people who have sub-F5-phobia and yes, I am considering seeking therapy for it).
Jeff B, from an online thread entitled: How hard is it to make a reflector as good as mid-price ED or Apo refractor?
I have one mount and two great scopes-an APO and a reflector. I usually go a month or so with one and then a month or so with the other.
After a month with the reflector I’ll switch to the refractor and notice how pretty the stars look all across the field.
After a month with the refractor I’ll switch to the reflector and achieve higher mag than is possible with the APO.
I’m not sure I could call one a favorite but I like the refractor for any outreach situation. It just seems easier for the uninitiated.
Steve O (Wichita, Kansas), from an online thread entitled: How hard is it to make a reflector as good as mid-price ED or Apo refractor?
I had a mid 1960’s vintage Cave Astrola Deluxe 10″F7 reflector and a GSO 10′ F5 dob and they both showed the same amount of detail on the planets. The ONLY difference was that the GSO showed a little coma whereas the Cave operating at F7 didn’t. They were both outstanding scopes and any differences other than the above noted were essentially splitting hairs. It is quite possible to get a Chinese optic that is outstanding. My current 6″f8 is a testament to this fact. I think over the last 15 or 20 years, the quality control has gotten a lot better and the chances of getting a lemon are far less but I’m sure the occasional one still gets through.
Barbie, from an online thread entitled: Premium mirror versus Chinese mirror.
I have also found that it’s much easier to find and purchase sensibly perfect (SP) refractors off the shelf than SP reflectors, which are usually only available from a few small custom shops. Custom SP reflectors are very expensive compared to off the shelf scopes. They have longer lead times, and some sizes, 6”f8 for example, are not available.
Why? I believe that most people are satisfied with the optics and mechanics of production reflectors at 1/10 the cost and don’t want to wait months for delivery, so the market for SP reflectors too small to be attractive to large manufacturers who stay in business by selling people what they want to buy at a price they are willing to pay and do it efficiently enough to make money.
For example, my factory 8”f6 Dob cost me $300 and was delivered to my front door by a big brown truck within 48 hours of placing my order. My custom 8”f6 reflector with sensibly perfect optics cost me $3,000 and delivery took a year. Its optics were better, but the improvement was subtle, usually requiring side-by-side testing in better than average seeing to confirm.
On the other hand, the optical improvements to be had from a 10” factory reflector costing $600 are immediately obvious, so more people are inclined to upsize their reflective optics rather than upgrade them. Other people who are basically satisfied with their mass produced factory reflector optics might prefer to spend the same $3K on a SP refractor, not because it’s better than a reflector, but because it complements a reflector so well, it’s available off the shelf, and it scratches the SP itch too.
gwlee (California), from an online thread entitled: How hard is it to make a reflector as good as mid price ED or Apo refractor.
My personal experience has been that my dirt-cheap 10″ GSO Dob produces better planetary images than my 4″ Apo that cost well over 10 times the price. Yes there is some diffraction, but the increased resolution, brightness and higher possible magnification compensate for this.
There is definitely a point where a good reflector (probably Newtonian) must overtake any practical Apo (i.e. <=6″ for most mortals). I suspect this point is probably achieved with premium reflectors >9″-10″ aperture.
JohnGWheeler, (Sydney, Australia), from an online thread entitled: How hard is it to make a reflector as good as mid price ED or Apo refractor.
As of last night I now have some direct experience relevant to the question at hand . . .
A seller had got together the parts to build an 8″ F7, had sold it to a second guy who was more of an imager and decided not to go ahead with the build. I was the third in line, and I finally got it put together.
Parts are an 8″ F7 Zambuto quartz mirror (made in 2016), a 1.3″ 1/30th wave astrosystems secondary with holder and four vane spider, 10″ x 60″ parallax instruments tube, and a moonlite single speed focuser. It also came with a Meade cell that I upgraded to a Aurora precision cell, and I had to get flocking, rings (parallax), and a dovetail plate.
After two days of drilling, filing, screwing, sticking, and flocking (and probably several other ‘ings’) I now have a fan-bleeding-tastic 8″ F7 Newtonian for something in the neighborhood of $1600.
I made mistakes along the way. I miscalculated the placement of the spider/secondary, and so had to source a longer bolt for the secondary. I got lucky with some old plumbing parts that serve as a ball joint at the end to pivot the mirror for collimation. I messed up a measurement on locating a hole for the spider, and my flocking job doesn’t look completely pretty, but it works.
First light was yesterday afternoon on the moon. Seeing was so-so. High frequency fuzz that makes it seem that the focus is always out interspersed with brief moments of stability. Jupiter finally got high enough for a look around 10:30 PM . . . poor to moderate seeing, but WOW! Exactly what you’d expect from these optics. GRS was bang in the middle of the planet, and very obviously off-pink colored. Numerous bands and a big blue barge visible. Brief moments of very good seeing and I was up to ~300x.
So how does it compare . . . well, it blows my Televue 101 out of the water on Jupiter and the moon. In fact, it blows my old 6″ F8 triplet apo out of the water, and provides nicer contrast by far than I ever saw in my 11″ Edgehd, albeit with less illumination. And compared with my 12.5″ F5 (Zambuto again) Portaball, well not quite as good as that, but the Portaball would still be thinking about cooling when the 8″ was throwing up great views.
areyoukiddingme (Santa Barbara, California), from an online thread entitled: How hard is it to make a reflector as good as mid price ED or Apo refractor.
Bigger Newts will always beat out smaller APO’s on cost and image detail on planets if they are built good. Now compare a 8″ APO to a 8″ Newt and the APO is gonna win, but at 20 to 30 times the cost of the Newt.
CHASLX200(Tampa, Florida); from an online thread entitled; SW MAK 180.
Others will advise a moderate-sized reflector as affording wonderfully fine views of the Moon and planets. The question of cost is greatly in favour of the latter construction, and, all things considered, it may claim an unquestionable advantage. A man who has decided to spend a small sum for the purpose not merely of gratifying his curiosity but of doing really serviceable work, must adopt the reflector, because refractors of, say, 5 inches and upwards are far too costly, and become enormously expensive as the diameter increases. This is not the case with reflectors; which come within the reach of all, and may indeed be constructed by the observer himself with a little patience and ingenuity.
*My 10-inch reflector by With-Browning was persistently used for four years without being resilvered or once getting out of adjustment.
William F. Denning, Telescopic Work for Starlight Evenings (1891) pp 38-39
An amateur who really wants a competent instrument, and has to consider cost, will do well to purchase a Newtonian reflector. A 4 1/2-inch refractor will cost about as much as a 10-inch reflector, but, as a working tool, the latter will possess a great advantage. A small refractor, if a good one, will do wonders, and is a very handy appliance, but it will not have sufficient grasp of light for it to be thoroughly serviceable on faint objects. Anyone hesitating in his choice should look at the cluster about χ Persei through instruments such as alluded to, and he will be astonished at the vast difference in favour of the reflector….. When high magnifications are employed on a refractor of small aperture, the images of planets become very faint and dusky, so that details are lost.
William F. Denning, Telescopic Work for Starlight Evenings (1891) pp 41-42
Perhaps it may be advisable here to add a word of caution to observers not to be hastily drawn to believe the spots are visible in very small glasses. Accounts are sometimes published of very dark and definite markings seen with only 2 or 3 inches aperture. Such assertions are usually unreliable. Could the authors of such statements survey the planet through a good 10- or 12-inch telescope, they would see at once they had been deceived. Some years ago I made a number of observations of Venus with 2-, 3- and 41/2 inch refractors and 4- and 10-inch reflectors, and could readily detect with the small instruments what certainly appeared to be spots of a pronounced nature, but on appealing to the 10-inch reflector, in which the view became immensely improved, the spots quite disappeared, and there remained scarcely more than a suspicion of the faint condensations which usually constitute the only visible markings on the surface.
Concerning Venus: William F. Denning, Telescopic Work for Starlight Evenings (1891), pp 151
Coma is essentially negligible at F/8. It’s there, and can be seen in my 2″ widefield eyepieces, but it’s very muted, even compared to my F/6.24 8″ GSO, to say nothing of the multitude of F/5 and faster mirrors out there. The SkyWatcher 6″ traditional dobsonian makes a nice lightweight alternative when I want something quick to setup, but with enough aperture to wow people on the planets and such. The SW6 makes owning a 5″ refractor obsolete, in my opinion, all while providing the great dobsonian stability that handles the West Texas winds so much better than anybody’s refractor that’s not in an observatory, or using a mount that’s ridiculously heavy and expensive (to say nothing of the accompanying 120mm+ ED glass tube). Yes, it will have less thermal stability, like all reflectors compared to refractors, but that’s a problem one might resolve with a cross-mirror fan, and would be a whole lot cheaper to implement than a big mount, ED glass, etc, without affecting general portability very much.
I like reflectors, and especially dobsonians, for their ease of setup and use. I have always preferred the eyepiece-at-the-top-&-angled kind of design ergonomically, and the general dobsonian design, with the weight at the bottom of the tube, cannot be emphasized enough how wind resistant it is compared to a refractor’s flying in the air like a flag setup. This comparative difference was demonstrated to me Saturday night, when I had out my SW6″ for its maiden sky-voyage and an often-used Kunming 102mm F/7 refractor on the GSO SkyView Deluxe Alt-Az mount. Although it wasn’t very windy that evening, we still had some, and every wind produced a light dance in the refractor, and only a little wiggle in the dobsonian, which dissipated much, much more quickly than the spasmodic gyrations of the image in the refractor.
I will have to decide if I want to sell my most excellent Z8 and replace it with a GSO-10″-dob-and-Coma-Corrector or not. That’s a different story, and would involve comparing dobsonian performance to 6″+plus refractors, which are, to my line of thinking, insane and off the table, cost and mount options considered. But I believe the stories I’ve read here on CN, that a 6″ reflector can keep up, visually, with 5″ ED refractors. I’ve seen for myself how much better Saturn appeared one evening long, long ago, in a LB8″ dob compared to an Orion 120mm ED scope. No comparison, really, the 8″-er was that much better, so I’m sure one would have to move into the refractor stratosphere to continue competing with dobsonians above 6″, and why I’d never own such a refractor. But the SW6, especially if I can upgrade the rather inferior Synta 2″ rack and pinion it comes with, puts all the performance of a 120-127mm refractor into an easier to manage, more stable package, at a fraction of the cost.
CollinofAlabama (Texas, USA), from an online thread entitled; Of coma & 120mm ED refractor.
The best telescopes known to amateur astronomers have a thin aluminum coating supported by glass, diameters considerably exceeding the largest apochromats, and are at their best under dark, steady skies.
Alan French (Upstate New York, USA), from an online thread entitled, Comparing FPL-53 and CaF2
It is worth remembering that Stanley Williams and Elmer J. Reese, whose names stand very high in the list of students of the planets, did most of the work for which they are remembered with reflectors of less than 20cm aperture. One of the authors(W.S), while at home from college in March 1978, made an independent discovery of a new SEB disturbance with a 20cm reflector. There was nothing extraordinary in the feat; it was simply a matter of looking at the right time and knowing enough to recognize the significance of what was seen.
William Sheehan & Thomas Hockey, Jupiter, Reaktion Books, 2018, pp 161
Well after sitting in my living room corner for several weeks after purchase I managed to get out last night with an Orion XT6 dob, now this is the basic one, 1.25″ focuser, no eyepiece rack and just the one eyepiece, lots of eyepieces already so its not needed anyway. I bought this on a whim new for less than what I have paid for a mid range single eyepiece, $300 Canadian taxes included, free shipping. I,m older and weight was an issue so the 6″ made more sense than the 8″ which I owned many years ago so I was aware of the weight and bulk of it, also the 6″ will live in a small upright tool shed I have for gardening stuff. Just lift it out and use it.
Lots of light pollution where I live so I tend to observe the moon and planets so after adjusting the secondary (it was way too far towards the primary) I turned it onto the moon.
Well it looks like I got a good one and I came in at 1:30 pm when both it and Jupiter fell behind the trees, tremendous detail on the moon and sharp crisp views, I like a lot of others have over the years got wrapped up in complex and expensive gear so have a night like this for a modest outlay was a delight, I found it really worked well with some of my lower cost eyepieces, higher grade ones made a difference but not that much.
Binojunky, from an online thread entitled Cheap small Dob Delight.
The XT6i was my default recommendation to newcomers who were confident they would enjoy the hobby. Alas, Orion no longer offers the 6″ with IntelliScope. As Binojunky said, enough aperture to open the door to DSO, can handle magnifications I like to use on planets (200x-300x), light, easily carried, etc., etc. It’s also the perfect size for kids who are old enough to “drive” by themselves. My son and I used one when he was ten. He liked that he could collimate it himself, use the IntelliScope computer himself and point the scope himself. He just wished it tracked.
macdonjh, from an online thread entitled Cheap small Dob Delight.
I have owned three of each and still have one of each, both Orion. 6”f8 weighs 34#. 8”f6 weighs 41#. 7# doesn’t sound like much, but it’s a major difference for me at this site that requires a lot of tree dodging; 6” is very easy to use here; 8” is almost unusable, which is why I own the 6. Be aware that 6 and 8 weigh about the same with some brands, SW for example.
Focal lengths are identical, 1,200mm. 6s cools a little faster. All three 6s had a poor a quality 1.25” focuser. It can be adjusted well enough to be serviceable, but requires frequent tuneups. 8s come with an OK 2” focuser. Both are equally easy to colimate to the required tolerances using laser or collimation cap; theory suggests the collimation tolerances are more forgiving on the 6”, but I haven’t noticed a practical difference.
Optical quality (figure) of all of them were about equal, good to very good, no advantage to 6 or 8. 6” might be easier on inexpensive eyepieces, but I only use expensive EP, so can’t say from experience, but it’s consistent with optical theory.
With the same LP EP in both scopes, the 6” has a smaller exit pupil, which is a bit more compatible with the astigmatism in my eyes, so star fields seem a bit sharper to me. At the same exit pupil stars are equal[ly]sharp to me in both scopes. I doubt a person without astigmatic eyes would notice a difference.
The larger 8” is a noticeably better optical performer an all targets, but especially DSOs. Noticeable, but not wow! I also believe the 8s have slightly better motions, but it’s subtle, and most people probably won’t notice the difference if they don’t have the opportunity to use bith scopes side-by-side. For sites where I can carry the scope out in two pieces and leave it in one place all night, I prefer the 8.
gwlee(California), from an online thread entitled Cheap small Dob Delight.
I was quite lucky when I bought my 6″F8 Synta(Orion) xt6. Its optics are so good that I don’t really need a premium mirror maker to make me anything better since my Xt6 shows a textbook star test and has been lab tested to be of excellent quality. Perhaps the Chinese have really gotten the 6″F8 optics to a very high level of performance and Zambuto knows this which is why he doesn’t make anything smaller than an 8″. Perhaps not, I don’t know for sure but all I can say is that my 6″f8 shows me fantastic views of the planets rivaling those of my apo refractor [100mm f/9 ED], but with a little more light grasp for deep sky objects. About 20 years ago, I had a Bushnell 6″F8 Dob and it was just o.k. Fast forward to the present and my current 6″F8 dob, the difference is like night and day in optical performance and mechanics so I would say the Chinese have improved by “light-years”, at least when it comes to making 6″F8 mirrors.
Barbie; from an inline thread entitled;Why won’t Zambuto make 6″ f/8 mirrors.Truth Please
Did a public star gaze on the beach last Friday and Sat night. Took my 6 inch f8 home built dob out there.
Haven’t done any such gazes in years and back when I did I was hauling out the 10 f5.6 “big dob”.
Turns out the 6 inch f 8 is the perfect outreach scope as well !
There was a C8 celestron. A 9.25 something or other cat. A 4 inch relatively fast ED refractor. Some other guy with another C8 ish type scope set up with a display screen and astrophotography.
Then, off to one side was my little 6 inch F8 Dob.
A fair fraction of the folks that looked through my scope made a point of saying that they were attracted to the scope and wanted to check it out.
And I can think of several reasons why. First obviously home built. Not nearly as impossing as the other scopes. Even the 4 inch frac had a serious looking mount. Not complicated looking. Those other scopes with all those fiddly bits and hand controllers and whirling motors are fairly intimidating to the general public I think. And needless to say the astrophoto/display screen scope took that to the next level.
Not only did it look simple…folks could see it was simple in use. Look at Jupiter say. Then swing around, sight along the side of the tube or use the laser pointer on the tube and bammmm….now we have Saturn….swing around again….Venus….swing around again…Alberio…swing around again…the moon…and so on and so on.
Need to move the scope to get an unobstructed view of X? Pick it up….move over…plop it back down….bam….done.
Most people expressed awe that I could “just find” things. But I explained things…simple landmarks in the sky. Albierio….end star of the easy to see Cygnus. M4…sorta between Antares and that other star. M22…forms a parallelogram with the handle and top of Scorpious the Tea Pot. M57….right between those two easy to find stars near easy to find Vega. Explained how Mars, Jupiter, and Venus are fairly obvious targets once you know what you are looking for. And even Saturn with a little care.
Then a fair number got fairly interested in the home built aspect. Hey, I just bought the optics and built a wooden box ! The side bearings are PCV flanges…look here the focuser is made of plumbing parts….you can do this too…especially with all the info and help on the internet these day….
Hey, how much does this cost? Ohhh, you can get something like this for around $300. A bit more and you can get an 8 incher ! The 4 inch frac cost about twice that (the tripod alone was $300). The other scope…well, more like $3000 rather than $300. They probably didn’t wanna know what the imager guy had invested.
As for views? The 9.25 showed a little bit more detail on Jupiter…but it was all a bit washed out to me (probably that large secondary mirror doing that). The six f/8 dob beat everything else IMO. And this is just some random mirror I bought 25 years ago with a bog standard diagonal. Have never even star tested it. And the eyepieces….my $10 Vite 3 element/plastic lens 10 and 23mm plossls.
End of the night. Put the tube under one arm…grab the handle on the rocker box and walk to the car in the parking lot. Easy peasy.
I think a lot of people came away less intimidated about telescopes and costs and finding things in the night sky after seeing the little dob in action.
Starcanoe; from an online thread entitled; Cheap small Dob delight.
I built and enjoyed this 6-inch F/7.3 before I even knew what a Dobsonian was. But it’s really close to that concept. Enjoyed that for a long time, added setting circles and wroth my own calculator program to point at things. Used that for years on planets, clusters, nebulae, etc. It was wonderful! I would take it in my compact car to star parties. Very convenient. Sure, I eventually went bigger… but your point is a good one. There is a LOT to be said for starting out with this size and doing visual.
TOMDEY( Springater, New York, USA): from an online article entitled: Versatility of a 6″ Newt.
A 6″ f/8 holds a special place in the hearts of us older amateurs. The classic RV-6 Criterion is the poster child for the 6″ f/8s. Many had exquisite optics and the planetary views were quite memorable. I was interfaced with an RV-6 in high school (I graduated in 1970) – the school owned one and it was superb.
Yeah – yeah, that’s the nostalgia talking.
Today, with the Dobs, I would say that the modern equivalent is the 8″ f/6. It’s not that 6″ f/8 is any less worthy a telescope than it was 50 years ago – it is still a wonderful telescope to own. But nowadays the 8″ f/6 has such a small differential in price to the 6″ f/8 that it makes sense to get that instead for most folks. Both telescopes share the same 48″ focal length. So both are manageable as far as size is concerned.
Siriusandthepup(Central Texas, USA): from an online article entitled: Versatility of a 6″ Newt.
I agree with siriusandthepup that while a 6-inch f/8 Dob is a great scope for beginners — and for experienced observers as well — an 8-inch f/6 Dob is even better. The 8-incher is very nearly the same size as the 6-incher due to its shorter focal ratio, and is quite a bit more capable. The only real advantages of the 6-incher are that it’s somewhat lighter and cheaper and significantly more forgiving of poor collimation. But once you learn how to do it, collimating an f/6 scope should take well under a minute in most cases.
As it happens, my own scope is halfway in between — a 7-inch f/5.4 Dob. It’s a total joy to use, in every way. I can carry it easily in a single trip and set it up in a matter of seconds. Its ergonomics are miraculous — completely stress-free observing while sitting in a standard chair for objects almost from the zenith down to 20 degrees above the horizon. With a 2-inch focuser, it has an amazing widefield capability, fitting and framing objects like the Pleiades beautifully.
On 90% of all nights it shows almost as much planetary detail as my 12.5-inch Dob. Under dark skies, it shows hundreds of deep-sky objects with ease, resolves at least a dozen globular clusters, and shows a great deal of detail in nearby spiral galaxies such as M33, M51, and M101.
Tony Flanders (Cambridge, MA, USA): from an online thread entitled: Versatility of a 6″ Newt.
I have been using a celestron c102 4″ f/10 refractor for weeknight hour-long observing outings. With the planets well placed they have been getting much more time lately. However, I find the CA quite bothersome (perhaps spoilt with my other scopes Nexstar 8 GPS and 12 inch dob – naturally color-free but more cumbersome to set up than the 4 inch frac).
I have been eyeing the At102ed as the natural solution to my problem, and a while back was able to compare the views between the two scopes. Another person present at the club outing had a 6-inch f5 reflector with 2 inch focuser and type 1 paracorr.
The reflector provided best views of saturn and jupiter – bright, sharp and color-free. It was slightly better on globs like M13 (obviously due to the slightly better light grasp). With the paracorr it was also an amazing wide-field instrument. Just a slight step behind the At102 in FOV department, the paracorr-corrected views were brighter and more engaging to me than the At102ed. It displayed all the portability advantages of At102ed, had better color correction, and provided slightly better wide-field performance but with a slightly smaller wide-field FOV.
Going by memory (as I had not set up the C8 side-by-side that night) I’d rate the views of the 6″ reflector far closer to the C8 than to 4″ refractor.
I was about to pull the trigger on At102ed, but I found the 6 inch f5 more satisfying. Although a 4″ ed better compliments my existing line-up, the 6″ f5 is a better stand-alone scope.
eklf (Carrboro, North Carolina, USA) from an online thread entitled: Versatility of a 6″ Newt.
I am all about aperture most of the time.That being said, my 6″ is a keeperI have seen spiral arms of M51 in it and fanstastic planetary observing as well. Under dark skies it is a very capablle little scope.Even after getting a 15″ I have sometimes used it for conveniece or neccesity and it has not been ” too bad I can’t use the 15″ scenario.It satisfies.Easy forgiving collimation, very quick cool down and super easy to transport.Odds are you will have good to great optics as well. Outside of Quasars it shows all of the types of objects out there.
aatt (Connecticut, USA), form an online thread entitled: Versatility of a 6″ Newt.
Definite pros and cons to different sizes. Mass produced costs less, though. With 8″ f6 vs 10″ f5, both should be moved in 2 pieces. But the 8″ can moved in one piece if you really need to dodge a tree. Still, you will want more aperture.
6″ is enough to get interesting views. M13 starts to break up. Planets start to get beef that the 4″ can’t muster. The view is wider. And the scope is portable. But 6″ is mainly a grab n go. If you drive way out some place dark, you will want a 10″ to enjoy the night. Even at home, the 10″ will be much better on planets.
Stargazer193857(Southern Idaho, USA), from an online thread entitled: Versatility of a 6″ Newt.
Webster telescopes has a 14.5″ f4.5 with a Zambuto mirror, you can upgrade to a quartz mirror for even better planetary views. I’ll bet with the Zambuto quartz mirror it would give better planetary views in good seeing than the TOA 150. Deep sky objects would be no contest.
Astro-Master: from an online thread entitled, Visual Only: 150mm Triplet APO vs 14″ Dobsonian
I would vote the 14 as well (if it is a good mirror), but the Tak may be the nicer built scope (definitely more pricey). With the budget of the 150, you could easily get a top quality premium primary and secondary mirror set and dominate the optical performance of the 150 (16″ or 14.5″ Zambuto/Lockwood/Lightholder/etc(other good makers). with 1/30 wave antares secondary, feathertouch focuser, cooling fans, etc. etc.). With the budget of a TOA 150, you could get a TSA 120, TOA 130, or TEC 140 and a nice quality dob.
To strictly answer your question and assuming the mirrors in the obsession are good,
On a good night with good seeing, both scopes will perform well. Coma will dominate the edge of the field in the dob unless it is corrected with a coma corrector.The Tak will be a easier to set up. The obession will take longer to cool down (especially true if it is a 2″ thick mirror). The 14″ will need to be collimated accurately before every use (recommend a good collimator like Glatter laser and Tublug barlow attachment). Stars may appear sharper in the TOA 150 (I have never used one, but I would expect this result), but you will see a ton more stars and even fainter stuff in the 14. The 14 will also have more resolving power to split tight doubles, and the 14 will be able to handle more magnification on planets. If the seeing is not as good, the TOA may perform better on planets with a sharper image. Also the TOA should cool much faster. I would expect the image to break down faster at high magnifications with the TOA than with a well collimated and cooled 14″ dob.
If you want to do any photography, TOA no question. For visual only, it depends on the circumstances, but I would take the 14.
Jakecru (Nevada, USA): from an online thread entitled,Visual Only: 150mm Triplet APO vs 14″ Dobsonian
To me a Dob and apo are complementary scopes, as each is better at different things. The Dob will go a lot deeper, and will be much better for most deep sky objects IMO. Definitely the scope of choice for globular clusters, planetary nebulae and galaxies (except perhaps Andromeda). The apo will have a wider field of view, and will be generally better for larger extended objects, and rich field observing. The apo will generally yield more aesthetically pleasing views of stars. On planets the apo will give a pleasing view unless the seeing is bad. The Dob potentially has more of an upside on planets but a lot of things have to go right for it to give nice planetary views, including good thermal control and good collimation.
turtle86, from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.
Get the large dob + a 4 or 5″ refractor for wide field.
AxelB( QC, Canada), from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.
Not just brighter, but far more detailed. I’ve had views of planets through large Newtonians, notably Mars and Jupiter, under exceptional seeing that can simply not be duplicated through any 150mm apochromat.
Alan French, (Upstate New York, USA); from an online thread entitled; Visual Only: 150mm Triplet APO vs 14″ Dobsonian.
I think we have to be careful with generalizations when commenting on APOs vs. Reflectors.
While I generally agree with what is being said we need to be careful to separate the subjective from the objective and also ensure we are comparing instruments of comparable quality / cost irrespective of design.
Subjectively, yes you could say the view in an ED apo is better but objectively a 14″ will have significantly higher light grasp, resolution and contrast vs. a 6″. There is just no competition.
On my second point….
My 14″ has a high strehl mirror and a 19% obstruction secondary. It costed me the same as a premium 6″ APO (but still much cheaper on a $ / aperture basis). With the coma corrector the views it produces are just sublime – pinpoint stars and no coma anywhere in the fov even with my 82deg 30mm. The airy disk is so tight it is almost indistinguishable from an apo.
In excellent seeing I can see festoons within festoons on Jupiter and swirling clouds within the GRS – views that are unmatched by any 6″ apo. I doubt even a 8-10″ apo will come close.
But I still use my 4″ and 5″ refactors and my C9.25 more simply because they are “easier” given my limited time. The 14″ comes out on the weekends or on dark site trips. To me the refactors have a completely different value proposition.
Astrojedi(Southern California, USA); from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.
I’ve previously reported running my TOA150 up against Cotts’ 12″ with Lockwood optics.
On large structures – say like the Pleiades or other things bigger than a degree across and maybe the moon, the Tak wins. On everything else, the Dob wins easily.
If you want to shoot images, the Tak wins on everything (but you don’t want to shoot images.)
If you want to put it in your car, it’s roughly a draw – the Tak is smaller but it demands a considerable mount.
If you want to draw a lineup make new friends at a star party .. the Tak will supply all weekend.
Noisejammer (Toronto, Canada), from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.
Not unusual to get 1-2″ seeing here. I also observe from Mt Laguna ~7000ft elevation (which is about 50 minutes away) where on occasions I have experienced sub arc second seeing and Mag 6.8 skies. There with seeing better than 1″ my C8 shows an incredibly detailed Dumbbell nebula comparable with texture and detail reminiscent of my H-alpha shots of the nebula.
Even in average seeing from my backyard the 14″ significantly outperformed a very good 6″ APO I had. I sold that APO as it was simply too cumbersome to move and mount.
My personal experience suggests that there is simply no substitute for aperture in this hobby. But the reasons to acquire most scopes are driven more by personal preferences and not just objective performance criteria (which explains why I spend inordinate sums of money on premium refractors).
Astrojedi (Southern California, USA); from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.
No 6″ APO can come close to what my 11″ to 18″ Zambuto and OMI Newts have done on the planets.
CHASLX200 (Tampa, Florida, USA), from an online thread entitled: Visual Only: 150mm Triplet APO vs 14″ Dobsonian.
A few years back I compared my TEC 160ED to my 14″ XXg Dob/Newt, my experience was that ‘planetary included’ (I think Saturn was mostly used), as the seeing improved, the 14″ started easily / obviously pulling ahead. Is not often we get seeing good enough for that, but the difference was obvious to my eyes, and you can see which one was sold.
Counterweight (Portland,Oregon, USA) from an online thread entitled: Visual Only: 150mm Triplet vs 14″ Dobsonian.
Is anyone, including the OP, truly cross-shopping these two scopes? While there are some opportunities for overlap, I will take my Obsession 15” every night, with the caveat that it takes time for the mirror to acclimate and the set up and collimating requires additional time/effort. I’m content with my 8” reflector most nights. I do like my refractor better on doubles, but the 15” and 8” will split tighter ones. Incidentally, my seeing is not great, but I have excellent transparency and minimal cloud cover most nights and my focus is typically on DSOs and there is NO CONTEST.
Rare indeed is the night when using my 15” that I say, gee, I wish I would have brought out the 120mm—or even the 8”, which has a fantastic mirror, and curved vanes. Possibly, only when the session had to be curtailed early because clouds rolled in. With the 120mm I’m frequently saying to myself, boy, that would be better with my reflectors. The exception might be on nights when I want wide views or merely to surf the MW.
Get a used quality big reflector and a less expensive, but still quite capable doublet refractor and never look back.
Chesterguy (Stllwater, Oklahhoma, USA), from an online thread entitled: Visual Only: 150mm Triplet vs 14″ Dobsonian.
Hi everyone. As the thread starter I wanted to let everyone know I’ve decided to go with a big dob. I am considering the Obsession Ultra Compact 22″ with go-to, which is roughly the same cost as a TOA150 mounted on an EM400.
jag32, from an online thread entitled: Visual Only: 150mm Triplet vs 14″ Dobsonian.
No we should all be using 60 mm stopped down to 40 mm. That would show that nasty ol’ bad seeing.
I agree with you about aperture. I’ve been using EDs and apos paired with each other (such as 81 mm on 130 mm) and on larger instruments (81 and 102 on c8 and c14) and have yet to come away thinking: “Thank God I have this here four inch refractor to save the night’s planet viewing.” The aperture always wins. On SCTs I amend the concept, I think the common wisdom that one subtract the diameter of the CO to get the equivalent apo diameter is a good rule of thumb. But even so the bigger scope can deliver more color saturation and more deep sky.
gnowellsct, from an online thread entitled: Visual Only: 150mm Triplet vs 14″ Dobsonian.
I happen to own a Orion Spaceprobe 3 and have owned at least one 70mm F/10 achromat.
A 76mm x 700mm spherical mirror is 1/12 wave. There is no need for a parabola, a spherical mirror is a nearly perfect parabola. The refractor has 4 surfaces that must be precise spheres and unlike the reflector, the surfaces not only need precise spheres, they also need precise radii to work together.
I would normally prefer a refractor over a similar sized reflector but in this case, this 76mm reflector has some real advantages both optically and mechanically. One advantage to the Newtonian is that the eyepiece is at the upper end of the telescope, this means the tripod can be lower and more stable.
Jon Isaac (San Diego, California, USA), from an online thread entitled: 76mm reflector versus 70mm refractor.
I think a 6” f/6 Newtonian with a premium mirror on a solid alt az with under 30% of CO could be one of the best “have the cake and eat it as well” secrets in amateur astronomy. Low cost, sharp views on planets that easily exceed those of a 4” apo (I also use a 4” fluorite Tak sometimes), bigger focus sweet spot and the advantage of almost fully illuminating wide field eyepieces to provide nearly 3 degrees of field.
Ratnamaravind (San Diego, California USA), from an online thread entitled: 6″ f/6 Newt OTA for $169.15
My mass-produce 16″ GSO mirror is tested at 1/14th wave p-v, and it beats the heck out of my 11″ Zambuto.
The point is, a 12″ GSO mirror that is barely diffraction limited will still show a tremendous amount more, with more detail, than a 6″ Zambuto.
From what I’ve been reading, GSO mirrors are not all going to be like mine by a longshot, but most of them do a pretty decent job; with just an ok mirror, I’ll take that 12″.
Codbear (Navota, California, USA), from an onnline thread entitled: Zambuto/Royce vs Synta/GSO.
If you are going to quote me, quote everything I wrote that is relevant: I did say this:
“Getting the performance possible from a larger aperture is more difficult because of thermal issues and as aperture increases, seeing becomes more and more of an issue. “
The question I was asked was to explain to [you] about why the wave front error is scaled relative to the aperture, why larger scopes have greater resolution. That’s pure optics, there are times when the seeing will support the larger optic.
If the best you ever see is 2″ and all you observe is the planets and double stars, first, you have my sympathy.. And in that case, the 6 inch might be a good fit but as I recall, Vlad’s simulation said a larger scope was still advantageous. The actual diameter of the first minimum of the Airy disk of a 12 inch scope is twice the Rayleigh Criterion, that’s about 2.2 arc-seconds. And as experienced planetary observers like Alan French will tell you, even in poor seeing, there are moments of stable seeing where the large aperture can be used advantageously.
In my world, 2″ is rather poor seeing for viewing the planets, being south of the jet streams close to the Pacific ocean in one of the worlds mildest climates has it’s advantages. The greater resolution and contrast possible with a 10 inch, 12 inch, 16 inch scope can be used to a good advantage.
Last night I spent some time on the star Jabbah, with my 10 inch. It’s a pair of doubles, one is 1.3″, the other 2.2″ , both were wide clean splits, the seeing was well under 1″. The views of Jupiter and Saturn were quite nice in my 10 inch.. Viewing the planets, I generally stop at 410x, the 0.6mm exit pupil is quite dim. That’s where I stopped last night.
I did start the scope cooling with the fan running about an hour and a half before sunset. The scope just has generic Taiwanese optics, decent optics, I’ve split doubles slightly under 0.5″, that won’t be happening in a 6 inch.
John Isaac(San Diego, California, USA), from an online thread: Zambuto/Royce vs Synta/GSO.
An instructive reminder (and very sobering for refractor nuts) of the effects of an obstruction in Newtonian(and other) telescope optics by engineer and veteran astro-imager, Thierry Legault. See here for details.
Looks like you have some pretty nice gear already. Sell the DM4 and get an 8″ dob for observing.
Keith Rivich, (Cypress, Texas, USA), from an online thread entitled: 4″ ED refractor vs 6″ f/5 for visual on a DM4?
Both are really fine choices for grab and go and visual. I have both, and Both produce an image that is more alike than different.The refractor will be easier on cheap wide field eyepieces.The newt will give you more light to work with. I would lean toward the newt given the big price difference that you see.
vtornado, (Northern Illinois, USA), from an online thread entitled, 4″ ED refractor vs 6″ f/5 for visual on a DM4?
6″ F/5 wins in all areas (even FOV vs 900mm ED)
Nicolelouda, from an online thread entitled: 4″ ED refractor vs 6″ f/5 for visual on a DM4?
Henry from NZ, on 02 Aug 2018 – 01:49 AM, said:
The price differential between a newt and a 4” refractor is quite large where I am, so this is in newt’s favour. I do like the ease of use of a 4” refractor. What do you think?
Curious; I find a 6-inch f/5 Newt much easier to use than a 100-mm refractor, except for the cooldown period.
In all likelihood, the views of planets and other bright objects would be much the same between the two instruments, but if the Newt has a really good mirror, then it would be clearly superior. Not by a huge margin, however.
The main virtue of the 100-mm APO for me would be the significantly wider well-corrected field of view. Depending on the APO’s focal ratio, of course.
Tony Flanders (Cambridge, MA, USA), from an online thread entitled:4″ ED refractor vs 6″ f/5 for visual on a DM4?
I have owned a couple of 6 inch F/5’s and a couple of 4 inch ed/apo refractors. 6 inch F/5 Newtonians tend to get into SCT size central obstructions and thermal equilibrium is not a given the way it is with a refractor. I would go with the refractor because it’s more reliable, it’s provides nice views of the planets without waiting for it to cool.
Jon Isaac (San Diego, California, USA); from an online thread entitled; 4″ ED refractor vs 6″ f/5 for visual on a DM4?
The “Cheap Dobs” from the 5 and dime have gotten to be quite excellent, at least in sizes 12″ and under and I’ve seen them personally give the “premium” dobs a run for their money!!
Barbie, from an online thread entitled: Zambuto/Royce vs Synta/GSO.
6″ f/5 newt. To my eye though the 4″ ed will be sharp and high contrast, 6″ will out resolve it.
Izar187(43 degrees North), from an online thread entitled; 4″ ED refractor vs 6″ f/5 for visual on a DM4?
For what it’s worth –
A good friend owns a “premium Dob” company – and will put whatever optics you want in your telescope. His personal rather large Dob has a primary by one of the commonly noted premium mirror makers (not Z or R). He has seen them all and can have whatever he wants – and picked what he wanted. I’ve observed with this scope – and it performs!
He also sells Dobs with GSO mirrors – if that is what the customer wants. He has said that the recent GSO primaries he as gotten have been quite good. From my experience – this guy knows what he is talking about – and can tell a great mirror from a fair one.
While I suppose you can get a less-than-wonderful mirror from GSO – there seems every reason to expect many current ones will be very fine. If it is ‘junk’ – return it – or have it re-figured.
George N (Binghamton & Indian Lake, New York, USA), from an online thread entitled; Zambuto/Royce vs Synta/GSO.
I was observing Jupiter and Saturn at 250x with my 6″ F8 ‘Mass produced” optics Saturday night and they didn’t even break a sweat!! I could have gone higher but didn’t have the eyepiece/barlow combination available to do so. I’ve also had high end “hand figured” optics and mass produced optics at the same time and compared them side by side and found(after 50 years of observing and testing) that there is little to no difference between TODAY’s mass produced optics and the more expensive “hand figured” optics, other than cost and bragging rights!! Hand figured, mass produced, if it shows me what I want to see, then I’ll buy it!!
Barbie, from an online thread entitled: Zambuto/Royce vs Synta/GSO.
ALL of these mirrors have their place, it’s not a matter of one OR the other, just like there’s more than one brand and model of car. The GSO / Synta are great for their low cost. At some point of involvement in the hobby some people want better and the market is there to answer, whether it’s a premium mirror or a Feathertouch focuser. The mass market mirrors are getting better and better, and that’s a good thing, but my experience and the experience of many others is that they’re still not equal to one made by a master craftsman and probably will never be. The difference between them is getting smaller, but it’s real. The bottom line is use and enjoy whatever you have and don’t worry about what others choose to do.
bvillebob(Oregon, USA), from an online thread entitled, Zambuto/Royce vs Synta/GSO.
The right answer will depend on individual preferences. For me the answer is very simple… 10”. No 6” scope, even a premium refractor will show more than a 10”. A 10” of even average quality optics will do everything better. Period.
Astrojedi (Southern California, USA), form an online thread entitled, Zambuto/Royce vs Synta/GSO.
Premium mirrors are a marketing device, people buy them for bragging rights or piece of mind, or feel they deserve such luxuries,but the views they produce are only marginally better on some objects , about the same on most objects. Other variables ,especially seeing conditions, collimation,tube currents, eyepieces, stray light, local thermal issues, secondary, exc, etc, are far more important then the alleged smoothness of the premium ,gourmet mirror.Folks that purchase such stuff, probably also buy paracors,premium hand grenade eyepieces,top shelf collimation aides,fans, etc, they usually although not necessarily are better at controlling the variables I mentioned and thus get the more from their scopes then the average mass market guy, and hence better views that they will attribute to their magic mirrors.
tommy10 (Illinois, USA), from an online thread entitled Zambuto/Royce vs Synta/GSO.
After owning 12.5 and 15 inch scopes, I appreciate my 8” dobs much more. Now that I know what to look for, I’m seeing things that I didn’t know I could when I started out with my first Orion 8” dob. The amount of detail visible in galaxies is the most surprising. As has been said here many times before, all large scopes do is magnify galaxies, they don’t increase their intrinsic brightness. So now I try to see the galaxies as simply smaller versions of what I saw in my bigger scopes, and I’m seeing things I never thought I could. I just had to change my expectations, and observing techniques. I’m getting to the point where I don’t want an F5 scope of any size, because of my aging eyes and their short depth of focus. So for me, going smaller and slower with an 8” F6, or even a 6” F8, is not only doable, but probable, maybe in the near future. When I want to do some serious observing, I break out the 8” F9. I haven’t even scratched the surface of what this scope can do.
Galicapernistein, from an online thread entitled; Versatility of a 6″ Newt
6″ is enough to get interesting views. M13 starts to break up. Planets start to get beef that the 4″ can’t muster. The view is wider. And the scope is portable.
But 6″ is mainly a grab n go. If you drive way out some place dark, you will want a 10″ to enjoy the night. Even at home, the 10″ will be much better on planets.
Stargazer193857, (Southern Idaho, USA), from an online thread entitled: Versatility of a 6″ Newt
Long ago I had a 6″ F8 with 1/8 wave optics and it gave views comparable to my WO ZS110 refractor for planets but brighter on DSOs and not far behind my IM715D mak with a much wider FOV.
dscarpa (San Diego, California, USA), from an online thread entitled; Versatility of a 6″ Newt
There seem to be generalizations flying both ways and neither are fully accurate.
The premium mirror makers are not fly-by-night operators. They are folks who have established solid reputations over the years by producing quality optics. And for many observers these mirrors are very much worth it even with a little wait time. To me for example an excellent/premium optical figure is immediately obvious but I am still very satisfied observing with other scopes. Many here are not.
On the other hand Commercial mirrors receive more Q&A than folks here are lead to believe. Manufacturing technology and overall processes have come a long way in the past decade have improved in leaps and bounds. These days based on the sample set of very recent 20-25 Celestron and Sky-Watcher as well as GSOs that I have looked through the mirrors have been very good – almost 95%+ are diffraction limited. Most harmful issues actually arise from other factors in the scope – alignment, cooling, collimation, baffling etc. This is why differentiation for the premium mirror makers is now shifting to larger mirrors and/or faster focal ratios where the commercial operations are yet to catch up (and they may never go there).
To me the Op’s question is a matter of personal preference as much as it is of performance.
Astrojedi (Southern California, USA), from an online thread entitled; Zambuto/Royce vs Synta/GSO.
I have been involved with manufacturing (including toys) in prc for over 2 decades, I concur with Jon’s experience. My extended family in prc are challenged daily in finding quality products and truthful information. But with wages stagnating stateside, i understand why I too have fallen for the China price.I plan to take my orion xt10g to the grave.
waso29 (USA), from an online thread entitled: Zambuto/Royce vs Synta/GSO.
We are definitely spoiled in this age of being able to get telescopes shipped to our doors that once upon a time were restricted to the realm of a dedicated observatory, and affordable by the masses. I’m thankful for all of it, which is a large part of why I said yes to this little guy. I don’t know how regularly it will collect photons, but it can definitely serve a good purpose.
BlueTrane2028 (Bala Cynwyd, PA, USA), from an online thread entitled; “Junk” Orion Spaceprobe 3″
I’ll take a pic eventually, but a 3″ mini-dob has been made.
Used an 18″ length of 1″ black iron pipe, two floor flanges and a street elbow. Made a box to fit around the OTA to hold it and to bolt to one of the flanges, bolted the whole affair to a circle of wood I bought at Lowe’s.
Black pipe is way too much money, so I’m in it a few bucks more than I had hoped to be… but the little scope has already proved itself to be decent. The mount needs a little work yet but it’s not shaky which is obviously good. Optically, it may be that my eyes are good, or it may be that I know it’s there… but I swear I could see the Cassini division (barely) and some surface banding on Saturn with a 6mm Expanse eyepiece in this thing. It’s clearly not a deep sky scope, but it’s plenty fine as a quick grab.
I’m not sure what role it will play in my collection (since I have other quick grabs), but it’s now completely usable.
BlueTrane2028 ( Bala Cynwyd, PA, USA), from an online thread entitled; “Junk” Orion Spaceprobe 3″
My old 10″ f/4.7 Dob with Synta optics was there as well, now owned by a club mate. It definitely put up sharper high magnification images of Mars than the ED150 last night.
J.R Barnett (Petaluma, California, USA); from an online thread entitled: Update on my SW ED150 order.
I was just observing Mars,Jupiter and Saturn at 250x(I could have gone even higher but didn’t have the eyepieces/barlow combination available to do so) this evening with my Orion 6″F8 dobsonian and had some incredibly sharp and detailed views of these planets so I would say the Chinese optics are more than up to the task for serious astronomical observations where critical fine details are to be seen. The clear sky chart for my area was indicating average seeing and transparency but I easily saw the Crepe ring of Saturn with Cassini’s division sharply defined as well as multiple bands on the globe. Mars also looked good, although still not prime due the remaining dust but Syrtis Major was seen as well as the SPC. Jupiter featured numerous bands with festoons and the GRS. Also viewed Epsilon Bootis(cleanly split), Mizar/Alcor, Alberio and M29 all from heavily light polluted and haze filled skies. Not bad for an hour long session before bedtime!!
Barbie; from an online thread entitled, Zambuto/Royce vs Synta/GSO.
Yes, there is for me. Deep-sky observing really starts to come to life with a 10. And in good seeing, it outperforms the 5-6″ class ED fracs on planets. I think the 10″ dob occupies a unique niche among telescopes. Anything bigger becomes cumbersome to handle solo. Anything smaller leaves me wishing for something bigger too often.
If I had to live with just one scope, it would be a good 10″ dob.
Precaud (north central New Mexico, USA), from a thread entitled; Difference between 8 inch and 10 inch Dobsonians.
You have ruled out a 12 inch Dob. Maybe you could reconsider. A 12 inch gathers more than twice the light over an 8. You will notice quite a difference in all objects with a 12–if the optics are of good quality. I own a 12.5 inch Portaball, and it performs outstandingly on planets, globulars, open clusters, double stars, and fairly well on nebula and galaxies. Why would you rule out a truss tube? You could move up to a 12 truss from an 8, with ease of hauling, set up, take down, and storage. I store my 12 inch Portaball inside of my house on my side of the closet.
Gene T ( south Texas, USA); from an online thread entitled; Difference between 8 inch and 10 inch Dobsonians.
I like what Karl pointed out in the previous post. There is more than the aperture gain to consider. You make no mention of how far you plan to carry this scope or how often you plan to load or unload it. All factors to consider. I had a 10″ that was admittedly an older sonotube variety and it was HEAVY and had to be split into two parts in order for me to carry it any distance. I was younger and certainly fitter at the time. I currently have an 8″ that I can carry as a complete unit and can carry it for some distance without strain because of the lighter tube, mirror and base. I might be able to do the same with a 10″ from the same manufacturer, but it would be pushing it and I’m not getting any younger.
The point, which is often made here, is that there are always compromises. I find myself using the 8″ much more than my 15″ partly because of the ease of set up, even though the 15″ doesn’t take that long. Obviously if the night looks like it will really be great, I have plenty of time or I can travel to a dark site than it’s worth it for the greater light grasp and additional effort of the larger aperture otherwise one can find and enjoy quite a bit with 8″.
Chesterguy, (Stillwater, Oklahoma, USA); from an online thread entitled;Difference between 8 inch and 10 inch Dobsonians.
Same here I only own an 8 inch currently and will one day jump to a 12 inch solid tube! I think for my personal preference I would not want to setup a truss every time I had to observe. Nor would I want to spend the extra money on the truss style setup and then be forced to buy a shroud on top of that. I’m a true rookie but from what I have read a truss design up to even a 12 inch doesn’t seem to be a benefit once you consider the extra steps of setup. In top of that they don’t seem to drop weight at all compared to solid tubes as far as I have read on the specs pages of any of the scopes I’ve looked at. They will definitely be easier to store but at the cost of not wanting to deal with setup? Not worth it. Buy solid tube avoid dew issues and body heat running through the shroud. That’s what I have learned from the forums I’ve read. Obviously far more experienced people out there than me but I’ve read a lot of what experienced people have to say.
Ken 83 (Connecticut, USA), from an online thread entitled; Difference between 8 inch and 10 inch Dobsonians.
I’ve got an 8 solid tube and a 12.5 truss. Guess which one I use twice per year at Cherry Springs and which I use often. From 8 to 12.5 is about one magnitude, so 8 to 10, I’m thinking is about half a magnitude.
Deep 13, from an online thread entitled: Difference between 8 inch and 10 inch Dobsonians.
…..the move to 10″ won’t give some improvement in viewing, but it is a half step at best, and may not prove to be as satisfying as some post suggest. Sadly, this is one of those things that people usually have to see for themselves to judge if it was worth doing. From 8″ to 12″ though is a much more obvious and dramatic step that anyone will see.
Eddgie, from an online thread entitled: Difference between 8 inch and 10 inch Dobsonians.
I will take the OP at his word that he’s done his homework and is satisfied a 10″ scope is all the upgrade he wants to consider. My C11 was a significant and noticeable improvement in viewing over some friends’ C8s. Familiar objects were brighter and more enjoyable to look at, AND objects that were too faint to be interesting to me opened up and became targets I sought out. Very worthwhile for me. Skip forward a few years to a shoot-out between my C11 and a 10″ scope. The 10″ scope won for cool-factor and my perception that the image wasn’t degraded by the loss of 1″ aperture. I sold, with a heavy heart, my C11 and kept the 10″.
That’s a long, round-about way of saying that for me, a 10″ scope is a worthwhile upgrade over an 8″ scope for deep sky.
To confuse things, I am perfectly happy with my 8″ driveway scope for lunar, planetary and double stars. I never used my 10″ or 11″ scopes at home because they needed my G11 which was a pain to assemble and set-up for an hour’s viewing (I know, not a problem for our Dobsonian-owning OP). My 8″ driveway scope requires only an Orion Sirius which I leave assembled and carry out of my garage in one trip, gives satisfying resolution (560x was not empty magnification on two near-perfect nights, 240x regularly), and provides images bright enough to trigger even my lazy color receptors so Jupiter and Saturn are more than just yellow and brown. So, there’s my case for the 8″ scope, if you’re a lunar/ planetary observer.
macdonjh, from an online thread entitled; Difference between 8 inch and 10 inch Dobsonians.
Jupiter in my 10 inch Dob
Main reason (which I think but could be wrong): Good seeing with steady high altitude air. Planet high in the sky (winter).
InkDark(Quebec, Canada), from an online thread entitled; Your best view through a reflector.
For planets it would be through the 18″ f/5.5 dob I built in the early 90s. Looked at Jupiter on a night of excellent seeing using a 4.8 Nagler and 2x barlow giving 1058X. Felt like I was in orbit around the planet. The details rivaled Voyager images. Never saw it that good again.
Second was using a 14″ f/7 homebuilt dob 250 miles NW of Sydney Australia. I was touring the Small Magellanic Cloud and got stuck on the Tarantula Nebula. It was bigger and brighter than the Orion Nebula and it wasn’t even in our galaxy!! I used an OIII filter, UHC filter and no filter. It gave a very different look each way and was spectacular each way.
Don W(Wisconsin, USA), from an online thread entitled; Your best view through a reflector.
Best view of a planet: Jupiter at 456X due to superb seeing conditions So many details a drawing would be impossible plus albedo shadings on Ganymede
Saturn at 1123x due to superb seeing, in which “spokes” shadings were seen on the rings, and the C ring went down almost to the disc of the planet.
Uranus at 493x due to excellent seeing, in which a transitory white stripe was seen by a few of us.
Best view of a galaxy: M51, wherein the dark lane in the bridge was visible, the “D” shaped bright area around the companion and 3 fingers of faint extension and a feathered spiral stucture extending from the main galaxy on the side opposite the companion. Spiral pattern and clumps in the spiral arms all visible. Superb transparency, a very dark night, and good seeing conditions all together.
Best view of a globular cluster: M15 fully resolved to the center into tiny little pinpoints all the way across the field and even as it exited the field. Superb seeing conditions and excellent eyepiece.
NGC104 in which the predominant color of the cluster was yellow due to the high density of red giants. Superb seeing and larger aperture (18″)
Best view of a planetary nebula: NGC7009 (Saturn Nebula) with center oval details, outer glow and satellite “pods” visible at 493X. Excellent seeing and transparency.
Best view of faint stars: O/A/B giant stars in NGC206 in M31–superb seeing and darkness
Best view of a star cluster: NGC7789 on a night of superb seeing and transparency
Best view of a nebula: M20 on a night of great darkness and transparency: the blue area completely surrounded the emission part and the center stars in the emission art formed a long “L”. Superb seeing, transparency, and darkness
M17>M16 where nebulosity was tracked from one nebula to the other–excellent transparency and darkness
M17 with the nebula completely filling a 42′ field and the “swan” only a portion of the visible nebula.–superb transparency, seeing, and darkness.
NGC6888 where the large oval was filled from one end to the other with ropy tendrils and a tendril in the center made the nebula outline look like a Greek theta. Fantastic darkness and transparency.
The Veil nebula wherein the Witches broom handle looked like a tubular-shaped filligree of silver–superb seeing and transparency.
NGC2359 in which 4 extensions from the center bubble could be seen and thin striae of nebula covering the center bubble. Fantastic transparency.
M27 in which ropy “berms” of nebulosity could be seen surrounding the long oval part of the nebula–excellent transparency and seeing, allowing for a high power view.
M76, where the outer ansae joined to make it look like a 2-handled beer stein. Amazing transparency and very high power due to good seeing.
Eta Carinae in which the homunculus in the center appeared gold in color against a rose colored outer nebula (dark skies and 18″ aperture)
I could go on and on. Too many things to list.
Factors of importance: Transparency, Seeing, Darkness, collimation of the optics, cooling of the optics. When they’re all good—-MAGIC!
All views were in the 12.5″ except where noted.
(Starman 1) Don Pensack (Los Angeles, California, USA); from an online thread entitled: Your best view through a reflector.
Best planetary- Jupiter/Saturn same night in my 8″ Orion due to good seeing and slow speed of the scope
Best DSO – Orion Nebula in my 12″ Lightbridge (with custom mirror). Could see green, blue, and alot of structure detail.
Blakheaven( NE Oklahoma, USA), from an online thread entitled: Your best view through a reflector.
Jupiter and Saturn in my 6″ F8 dobsonian. Saw albedo features on Ganymede and 4 moons around Saturn along with Encke’s minima and the crepe ring and many swirls and festoons in Jupiter’s belts and with detail around the GRS. I was using 298X and could easily make out all of these features in the best seeing I’ve experienced in my locale in many years!! Along with the seeing, I also attribute the fine optics of my Orion Skyquest XT6, of which I have gotten an excellent sample!!
Best DSO: Orion Nebula complex during the winter of 2017 in my 40+ year old Japanese Erfle eyepiece in the aforementioned 6″F8 dob.
NOTE: My optics were perfectly aligned and properly cooled which I believe to be two of the most important factors in seeing these details.
Barbie, from an online thread entitled; Your best view through a reflector.
Jupiter in John Prattes 32” at the Winter Star Party a couple of years back. Everything I hear about the steady Florida sky was true that night. At 909x, the image scale was huge and the planet rock steady against the sky. It was literally impossible to describe what I saw, an image only rivalled by spacecraft flyby. Transparency and darkness were irrelevant, it was the steady sky and large, superb Lockwood mirror that made that view possible. A view I will never ever forget.
Every time I view an object with my 32” the first time, is basically a lifetime best view. Galaxies and Planetary Nebula in particular look incredible in the big dob. On a great night of seeing, at high power, the Homunculus at the heart of the Eta Carina Nebula looked like a Hubble image. That’s probably my favourite so far.
I get to observe where the sky is as dark as it can get, and the transparency is generally at the top end of the scale. But the memorable sessions usually occur when the seeing conditions are very good, which is hit and miss at my dark site. I would be happy to trade a little sky darkness for regular steady seeing. That combination and large and high quality optics make for the best combination.
Allan Wade (Newcastle, Australia); from an online thread entitled; Your best view through a reflector.
Saturn – 8″ Discovery dob w/ plate glass mirror was left outside all night with the top capped. I woke up before dawn, then used my 4mm Radian for a 300x view.
It was one of those very calm summer mornings where transparency wasn’t the greatest, but the air was rock-steady.
I could have watched it for much longer, but the sun soon came up.
Bill Schneider(Athens, Ohio, USA); from an online thread entitled; Your best view through a reflector.
Mars in the 20″ f/5 [Obsession] in 2003. The seeing was excellent and the detail was fantastic, with both moons visible at the same time as a bonus. Once the aperture is well into the large range, there is no substitute for superb seeing.
For DSO’s there have been so many moments that I could not pick a single target or even a single instance of a particular target. I got started on the path to the 20″ after viewing M51 through a 24″ Tectron in dark skies 20+ years ago. As good as the view was through the 24″, the eventual views through the 20″ have been sharper.
Redbetter, (Central Valley, California, USA); from an online thread entitled; Your best view through a reflector.
The best view ever was through someone else’s 18 inch(?) Dob of Jupiter at a star party, high up in the alps in Europe. It was one of the darkest skies available in the country where I was living, the telescope was expertly handled, and the mirrors well cooled I would imagine.
X3782, from an online thread entitled, Your best view through a reflector.
An 8 inch is a very capable scope and a can be lifetime scope for a serious observer.
Jon Isaac, (San Diego, California, USA); from an online thread entitled; Difference between 8 inch and 10 inch Dobsonians.
I have observed for ten years with an 8″ f6 dob. I do own a 12″, but the 8″ is my main scope and love it. I never stop learning about the sky with it. Maybe mine is so good because I didn´t buy it for Christmas?
But you are right, when I show the moon, Saturn, Omega Centauri or even a bright PN to a neighbor that has never observed through a telescope, they always say: “This is very nice, but if you only had 2″ more…”
Javier1978( Buenos Aires, Argentina), from an online thread entitled, Difference between 8 inch and 10 inch Dobsonians.
Can’t do just one.
Jupiter at 1100X (stacked Barlows) in the 18″ I owned at the time, late 1990s, very dark sky, excellent transparency and seeing. Jupiter full of detail, whorls, storms, bright color bands. At Blue Canyon.
M51 a blazing blue, at the zenith, excellent transparency and seeing, 18″, late 1990s, Blue Canyon.
Double quasar in Ursa Major, high in the sky, with my 22″. From an average sky, suddenly thee were so many stars it was hard to make out the constellations. It was February, the Double Quasar was high, found N3079 and immediately thereafter, at about 600X, the components were visible, seemingly pulsating at different rates. Great sky lasted for 20 -25 minutes. Lake Sonoma.
Eta Carinae, at Magellan Observatory in Australia, 24″. Most unique visual object for amateur telescopes.
Results of the spacecraft that crashed into a comet, I and two other observers saw “sparklies” for about 8 minutes after it hit (time adjusted for lightspeed). 18″.
Shneor( Northern California, USA), from an online thread entitled; Your best view through a reflector
Double cluster in 12” dob with 17T4 is one of my all time favorites.
Kadmus, from an online thread entitled; Your best view through a reflector
Quid est veritas?
My astronomical world changed forever when I first took a modern SkyWatcher 8″ f/6 Newtonian for a serious spin under a dark sky. It was far less expensive than any of the other telescopes I had personally owned, including some fine refractors and Maksutovs, and it outclassed them all on every type of celestial target. It was the sweetest of revelations! Modest and marvellous in equal measure, Newtonians are my instruments of choice, based solely on visual performance, when I want to pursue either serious or casual observing.
Justice, truth, fairness.
Neil English is author of Chronicling the Golden Age of Astronomy, due out late in 2018.