Buying an "Ultimate" Telescope:
Advice for the not so rich and famous

By Chuck Hawks


After over 20 years of amateur astronomy and managing a telescope dealership from the middle 1980's to the middle 1990's, I have had plenty of opportunity to refine my astronomical requirements. I have owned a number of astronomical telescopes ranging in size from a Meade ETX-90 (90mm Maksutov-Casegrain) to a Celestron Super C8 Plus (8" Schmidt-Cassegrain) with its associated equatorial wedge and tripod. As I write these words, I own a fine Stellarvue SV115T apochromatic refractor that is, for now, my ultimate telescope. I say "for now," because I have also learned that my needs may change over time.

Being a stocking Celestron dealer allowed me to experience a wide range of telescopes, from 60mm refractors to the massive C14 Schmidt-Cassegrain catadioptric (CAT). I also have some basic understanding of optics, having worked as a professional photographer for a good many years and taught photography at Lane Community College (Lane County, Oregon).

Your first telescope will very likely not be your ultimate telescope. You need to understand that, as your experience as an amateur astronomer grows, your wants, specific interests and needs will evolve. As your sophistication in this fascinating hobby increases, your ideas about what constitutes your personal ultimate telescope will change. Realistically, you will probably own several telescopes in succession, learning as you go along. At least it has worked that way for my friends and me.

I have learned that optical quality is the single most important requirement in any telescope, even before clear aperture. I have learned I need a portable telescope that I can transport to dark sky viewing sites. I have learned I do not like go-to (computerized) mounts on my telescopes. I live in a singlewide manufactured home where storage space is at a premium, so that is also a factor. Most of all, I have learned a telescope that is hard to use doesn't get used. Last, and perhaps most important, I have to be able to afford to purchase the telescope I decide upon without feeling guilty about spending too much money on what is, after all, not a necessity.

Recently, I decided that it was time to pull all of that hard-won experience together and write this article about selecting my ultimate telescope. I emphasize "my," because while I hope that reading about the process is useful to others, your ultimate telescope will probably be different from mine. Here are some factors to consider when contemplating an ultimate telescope.

  1. Type of Telescope - The usual choices are refractor, reflector (Newtonian or Cassegrain), or catadioptric. The latter usually means choosing between a Maksutov-Cassegrain (Mak) and a Schmidt-Cassegrain (SCT), although there are other conceivable possibilities. If you want a refractor, unless it is a long focal length planetary scope, to qualify as an "ultimate" your scope will need either a semi-apochromatic ED doublet objective or some sort of true apochromatic design with three or more lens elements, at least one of which is usually made from ED glass. These are expensive, but after all, we are planning an ultimate telescope.
  2. Quality - An ultimate telescope must be the best optical and mechanical quality that you can afford. Choose your list of potential manufacturers carefully.
  3. Visual or Photographic - Most astronomical scopes can do both, but if you are an avid astrophotographer your ultimate scope will require certain specialized attributes and accessories. Make sure they are available.
  4. Weight - Most of us need to be able to lift, carry and assemble our telescope and its mounting system by ourselves. With that in mind, how much can the heaviest component weigh? You don't want to strain your back every time you set-up your telescope. (Been there, done that and it's not fun.)
  5. Portability - Since most of us need to travel to dark sky sites for serious observing, the ultimate telescope needs to be comfortably portable by whatever means of transportation you use. Remember that the mounting system is going to be larger and heavier than the telescope itself.
  6. Convenience - Closely related to portability and weight, but not quite the same, is convenience. Do you also want your ultimate scope to serve as a "quick look" scope? This means that you can carry it outside, plop it down and look at something without a lot of hassle and set-up time. An equatorial mount is usually not good for quick looks, so if your ultimate scope should also suffice for quick looks, it should be adaptable to an alt-azimuth mount. Remember, a telescope that is hard to use doesn't get used.
  7. Type of Mount - The basic options are alt-azimuth (AZ) and equatorial (EQ). For serious observing from a dark sky site, I prefer an equatorial mount, but for quick looks, I prefer an alt-az mount. Equatorial mounts can be further subdivided into German equatorial and fork with wedge. Some scopes are available on either type of EQ mount (usually CAT's), while others require one type or the other. The mount is as important as the optical tube, so consider it carefully.
  8. Go-To (Computerized) Mount - Very popular today, computerized go-to mounts can find objects in the sky for you. Go-to mounts can be either the AZ or the EQ type. Obviously, go-to mounts require plenty of battery power if they are to be used in the field and they must be properly aligned or they will not work properly. Technophiles love go-to mounts, technophobes do not. I find that, among their other drawbacks (alignment, batteries and expense), they rob the user of the pleasure of finding new objects for him or herself, so I don't like them. Be aware that deciding for or against a go-to mount limits your mounting options.
  9. Storage Space - Where are you going to store your ultimate telescope when it is not in use? If you have a nice, dry barn or garage with plenty of available space, no problem. If you live in an apartment or other limited space, how you will store a telescope and its associated mounting system merits consideration.
  10. Clear Aperture - Since a good bigger scope will outperform an equally good smaller scope, you want the most clear aperture (light grasp) that fits within your other parameters.
  11.  Price - How much can you afford to spend for a luxury item like an astronomical telescope with its associated mounting system and accessories? Unless you are extremely wealthy, this effectively limits the available options in all areas.

Having established some guidelines for choosing an ultimate scope, I narrowed down my choices by addressing those 11 points this way:

  1. In the past, I have owned Newtonian reflectors, Maks, SCT's and refractors. At the time I chose my ultimate scope I owned a (semi-APO) Celestron Omni XLT 102ED and I was pleased with its performance. I decided my ultimate telescope should be an APO refractor.
  2. High-end refractors are produced by a relatively small number of specialty manufacturers. The sources I considered were Astro Physics, Astro-Tech, Stellarvue, TEC and Tele Vue. That is not to say that somewhat larger outfits like Vixen and Takahashi do not offer good refractors, because they do. I decided I would prefer mine to be assembled in the USA by a small outfit that has something approaching a personal relationship with its customers.
  3. As a professional photographer, I was attracted to astronomy because it was a visual hobby that didn't require taking pictures. I am only interested in visual performance, so I can optimize my ultimate scope for that without regard to imaging capabilities.
  4. The heaviest component I want to lift, carry and assemble should weigh no more than 20-25 pounds.
  5. I have to transport my ultimate telescope to dark sky viewing sites in my privately owned vehicle. This is an ordinary passenger car and I want my telescope system to fit in the trunk.
  6. I wanted my new ultimate telescope to serve as a backyard or quick-look scope. The equatorial mount that I prefer for extended viewing sessions is not suitable for this purpose, so my ultimate telescope must be adaptable (without a lot of fuss) to a suitable alt-az mount.
  7. My Celestron Omni XLT 102 ED telescope came with a CG-4 German equatorial mount and I found this manual mount to be about the right size for my purposes. The heaviest part is the equatorial head, which weighs 21 pounds. I wanted my ultimate telescope to fit on a mount like the Celestron CG-4 or CG-5, Vixen GPD2, Losmandy GM 8 S, or something similar. (I eventualy chose a Vixen GPD2 mount for my ultimate telescope, but that is another story.) Thus, the optical tube assembly should weigh no more than 20 pounds (also see #4).
  8. I have owned a computerized go-to telescope and I hated the mount, the alignment process, the batteries and pretty much everything except the optical tube. I have no interest in owning another.
  9. I live in a singlewide manufactured home, so storage space is definitely at a premium. When broken-down and cased for storage, the components must be reasonably compact.
  10.  Clear aperture rules, so I wanted a scope with more light grasp than my present 4" refractor. On the other hand, I have owned 6" and 8" scopes and found them too big and bulky for my purposes. I need an ultimate scope with a clear aperture between 4" (102mm) and 5" (130mm).
  11.  I learned long ago that economizing on optics is false economy. I am not rich by any means, but I was looking for a scope that I would not regret buying if I use it for the rest of my life. To me, that is the essence of an ultimate scope. I had the advantage of already owning a German EQ mount, a complete set of oculars and miscellaneous accessories, such as finder scopes and laser pointers. I was willing to budget up to $3600 (in 2009 dollars) for a basic telescope (optical tube with mounting rings).

My price range put some very nice refractors in the 4"-5" aperture range within reach. There are others that I would like to own, but simply could not afford. Ultimate APO refractors are expensive, no doubt about it!

My personal preference is for an APO refractor with what might be called a medium focal length for the type. Not an ultra-short "wide field" scope and not a scope so long it might be mistaken for anti-aircraft artillery. Something in the 750mm-1000mm focal length range, for example, given my 4"-5" aperture diameter requirement and the fact that I needed it to fit in the trunk of my car.

To summarize, I was looking for a true APO refractor in the 4"-5" aperture range with a medium focal length that weighs no more than 20 pounds from one of the American telescope makers. I want my ultimate scope to be compatible with a medium size German EQ mount for extended use and a decent alt-az mount for quick-look purposes.

I had my eye on the Stellarvue MG mount for some time ($499), which would be perfect for my quick look needs. Astronomy and Photography Senior Editor Gordon Landers owns several Stellarvue scopes and I have had the opportunity to use his version of the MG and found it to be an excellent mount. Gordon has been kind enough to let me use his Stellarvue SV102ED and SVR105-3 Raptor scopes and compare their performance to my Omni XLT 102ED. (We have previously reviewed all three of those scopes and the articles can be found on the Astronomy and Photography index page.)

Impressed by the performance of Gordon's Stellarvue scopes and his high opinion of the integrity of the Stellarvue organization and its founder Vic Maris, I began to study the Stellarvue line. Fortunately, they offer several alternatives that fall within my price and general specification range. These include the aforementioned SVR105-3 Raptor, as well as the SV105 Apo, SV115EDT, SV115T and SV130EDT. Stellarvue's prices include the optical tube, mounting rings, Vixen-style dovetail mounting rail, Stellarvue F2 multi-reticle red dot finder and heavy duty case. Even better, they give a $100 discount on any of their mounts when ordered with a telescope, so I could get my MG mount for an additional $399, rather than $499.

After spending considerable time perusing the Stellarvue web site (www.stellarvue.com), I ultimately ordered an SV115T-20 and an MG mount. The combo price is $3594. The SV115T is Stellarvue's top of the line 115mm (4.5") clear aperture scope. It uses a proprietary APO triplet objective with an Ohara FPL-53 ED glass center element and has a focal length of 800mm. The T20 version is supplied with a 2" Starlight Instruments Feather Touch dual speed focuser. (There is also a T35 version with a 3" focuser to accomodate those heavily involved in astro photography.)

SV115T Telescope
SV115T in Stardust White. Illustration courtesy of Stellarvue.

The SV115T20 has more light grasp than my old XLT 102ED (265x vs. 212x compared to the human eye) and weighs 13 pounds with mounting rings. The Vixen mount rail will slide right into both my Vixen GPD2 equitorial mount and the MG AZ mount. The scope's overall length is a few inches less than my XLT 102ED, so it will fit in the trunk of my car. The nice folks at Stellarvue had a single SV115T that had been special ordered in Stardust Blue (instead of the usual Stardust White) and not picked-up and they graciously consented to let me have it at no extra charge. (I prefer the looks of the blue scope!) All of my requirements were thus met.

I should explain in closing that I decided in favor of the 4.5" SV115T, instead of the tempting (and slightly less expensive) 5" SV130EDT model with its greater light grasp, because the latter was considerably larger and heavier, weighing 20.2 pounds with rings. Stellarvue considers the SV130EDT too heavy for their MG mount and I did not want a larger alt-azimuth mount. As it turned out, the SV115T seems larger in person than it did online. It is physically as much scope as I want to deal with and I'm glad that I did not order a larger scope. Life, you see, is compromise.




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Copyright 2009, 2010 by Chuck Hawks. All rights reserved.



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