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.
- 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
- Quality - An ultimate
telescope must be the best optical and mechanical quality that you can afford. Choose
your list of potential manufacturers carefully.
- 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.
- 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.)
- 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.
- 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.
- 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.
- 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
- 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.
- 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.
- 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:
- 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.
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.
- 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.
heaviest component I want to lift, carry and assemble should weigh no more
than 20-25 pounds.
- 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.
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.
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).
- 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.
- 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
- 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).
- 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 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.