irish@ihuxb.UUCP (Laura Sheldon) (07/02/85)
Many thanks to the people who responded to my inquiry about
telescopes and astrophotography. A surprise trip to Europe
has set me back a couple of weeks and many $$$, so I may have
to put off the telescope for a few more months.
Laura Sheldon
ihnp4!ihuxb!irish
Responses follow:
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If you are interested in telescopes try finding a local astronomy club and
go to some star parties - people tend to be very helpful. I believe Fermilab
has a star club and there are probably many others in your area.
It is very important that you have access to some very clear skies if you
wish to do astrophotography. My first telescope (a homemade 8" f6.3 reflector
made when I was about 14) lived in Montana and witnessed some wonderfully
clear skies. (the sky was so dark that it was difficult to pick out the
constellations due to an overabundance of stars - I remember thinking how
neat it would be living in a big city so you would just see the major stars -
fortunately those thoughts left long before I built the scope). Photograpy
was possible, but required a much steadier mount than I could afford. Now
that I can afford a good mount I'm stuck in NJ with its rotten skies (even
VT and NH have terrible skies compared with what was available in MT).
If you want something small (you'll probably have to drive a good distance to
get away from lights), check out the Celestron line of Schmidt-Cassegrains.
An eight incher will meet your price requirements and go in the back seat
of a car. The mounts on the Celestrons aren't good enough for serious work
and you may wish to buy just a tube and get something more robust from
other sources. The Clestrons tend to be about f10 and are reasonable for
planetary work and not quite as reasonable for nebulae work - you would want
something faster. The Rolls Royces of small scope are the Questars with
a Maksutov light path. They are wonderfully made and horribly priced. I almost
bought a 3.5" at an estate sale for $1400 and am still kicking myself for
not doing it. When I was an undergrad at the U of Utah a friend and I went
hicking in the Watsach mountains with his 7" (gasp - about $5k) Questar
mounted on a very light but sturdy mount. He packed the scope while I took
the the mount and batteries etc. That was some of the best observing I have
ever done.
The most bang for the buck - assuming you have a small pickup and very clear
skies - are the Dobsonian type scopes. These usually have a very thin mirror
with size rather than quality and a very simple azimuthal mount. I have used
13" and 29" scopes of this variety in California last year. The 29" produced
a view that was staggering - its eyepiece was also about 12' up. Such machines
are getting more popular with clubs and there may be one in your area.
Back to advise - visit/join a club, go to your library and get piles of Sky
and Telescopes, don't turn down your nose at small scopes of reasonable
quality and modest price to decide if the hobby is right for you 4-5"
Schmidt-Cassegrains from Meade and Celestron can be had for $600 - $800
and will give a reasonble view. Finally - if you wait until next May you'll
be able to find lots of scopes for very little $$$. People are going to
go into a buying frenzy getting ready for "THE" comet (not realizing that
binoculars are the best way to watch a comet) and will be disappointed how
Saturn and Jupiter look through their $1000 toy compared with the shots that
NASA gets.Scopes will get very cheap then as people unload them. Now if I
could only find interesting work in Montana or on the island of Hawaii...
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Before you spend those hard-earned bucks on a lot of fancy equipment,
make sure you know what you want and are willing to spend the time with
it to get your value of enjoyment from it. If you just go and buy a bunch
of nice-looking stuff that seems to be what you want, it will probably
wind up in your attic or closet collecting dust. Nobody, but nobody, can
tell you what you want but you. I would recommend:
1. Joining an astronomy club if you don't already belong. Here at
Holmdel we have a club, and members can borrow club-owned scopes.
This provides some important hands-on experience, you can get to
know about different kinds of 'scopes, what they are, and are not,
capable of. You also learn what kind of commitment it takes on
your part to observe those things you read about or see pictures
of. You must understand that what you as an amateur will see is not
what you see pictures of in ASTRONOMY or SKY AND TELESCOPE, etc.
You also have to put up with mosquitoes in the summer, frozen
fingers in the winter, changing your sleeping patterns so that you
are ready to observe at 3 AM, family or friends or neighbors who
wonder why you are sitting out in the lawn all night instead of
sleeping like "normal" people, lots and lots of coffee, bad weather,
etc. Of course, the rewards can be tremendous to those of us who
appreciate this science.
2. Subscribe to (or borrow) books, magazines or technical publications
on the subject. Many of the popular magazines are full of articles
on how to get started and the pitfalls of spending a lot of bucks
for something you later lose interest in. An astronomy club can
help here, also.
3. Find someone who is into observing and spend a few sessions with
him/her and get some experienced coaching. (Again, a club can help.)
4. Finally, from what I have seen, the smart thing seems to be to start
small (basic scope) and work up to more sophisticated (expensive)
capabilities such as astrophotography. I hear a lot of folk express
this idea. An inexperienced person, no matter how good the intent
or how serious you are, cannot buy your way into astrophotography.
It requires experience; otherwise you will be disappointed with
the results. Remember that the heavens have been there for a long
time and (hopefully) will still be there a few years from now when
you are ready to take your first pictures of some distant nebula!
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In answer to your question --
the Celestron series is probably the best for what you are looking for.
The C8 of Celestron is in the $$$$ range, depending where you get it.
Sky & Telescope Magazine is a good source for more info.
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I recently wanted to rebuild a telescope I made 25 years ago and found my
mirror was too far deteriorated. So I started looking around a little for
new equipment. Boy have things changed!! (I haven't been in the hobby for
maybe 20 years.)
If you are seriously interested in astrophotography you will certainly want
to look at the new 10" scopes that are around now. Celestron has been a
good (if not outstanding) name for many years. Relatively recently the
industry has perfected a type of design that was unachievable when I started
out with my Newtonian reflector. Celestron makes a beauty that a small
store over in Arlington, VA, is selling at ~ $1000. I can't remember the
name for the type of scope, but it consists of a 10+" dia. tube about
2 ft. long. The mirror is at the bottom with a hole cut in the center
through which the light passes to the eyepiece like the cassegranians.
But because the focal length is so short it has also at the top end a
lens that does a lot of image focus and correction. So the insides of the
tube is completely sealed from the external environment.
It can be put on several different mounting types. I still like the
equatorial mounts, although with the new computer control for some of these
you can use the fork type as well. Important to look for for photograpy are
slowmotion controls, good setting circles, clock drive, and illuminated
reticule for aiming. Usually you can get all this for about $300.
The shop in Arlington called it a "sale", so I don't know the regular prices.
The scope came with a carrying case and the mount broke down for transport.
I imagine the whole thing weighed about 40 - 50 lbs. total.
They even had one model that had a dedicated Atari computer with positions
of something like 5000 objects in ROM. You just typed in "M31" with the
date and time and presto, the computer aimed the scope and started smooth
tracking of M31. This was all for about $450 extra to the above equipment.
Sigh. I wish my tax return would let me go out looking more seriously.
This Celestron setup really looked good. The shop owner had one and showed
me a box of his photographs -- several of which were published in Sky and
Telescope.
If you want more on this, I'll go back and get exact details. (I'd like the
excuse to look around again.) I'd appreciate a summary of what you hear from
your posting -- maybe I'll really get serious about the hobby again.
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Here's my two cents worth (from over 25 years experience with
scopes of all kinds!):
Actually, before I could recommend a scope, I need more information
regarding your astronomical needs. You did mention a price range, and
you did mention astrophotography. However, most, if not all amateurs -
including astrophotographers - spend the majority of their time on the
scope using it visually. Do you plan to concentrate on deep-sky astro-
photography? Or lunar-planetary? Perhaps you are interested in wide-
field astrophotgraphy? As for visual needs, are you interested more
in gazing at the faint fuzzy nothings (FFN's) called galaxies, or are
you interested in planetary nebulae, splitting double stars, etc?
As you know, there are three basic optical configurations that you
can purchase:
1. Refracting telescope - These scopes utilize a lens for the
primary objective. For your price range, a 4" refractor is
about the largest you could buy. It would be portable, as well.
Advantages: It's relatively long focal ratio (usually f15)
make them excellent scopes for lunar, planetary, and double
star observing.
Disadvantages: Their relatively long focal lengths are not
that suitable to deep-sky astrophotography, or to deep sky
observing (mainly because of field size).
2. Reflecting telescope - These scopes utilize a mirror for the
primary objective. For your price range, an 8" reflector is
about the largest you could buy. Depending on the size of
your vehicle, it may or may not be portable. In this case,
you may opt for a 6" scope. (You will need to judge that).
Advantages: Reflectors have relatively short focal lengths
(f4 - f8), thus are excellent for viewing deep-sky objects
like star clusters and galaxies. They are quite a bit cheaper
than similar aperture scopes with different optical systems.
Disadvantages: The mirrors tend to need collimation fairly
frequently (easy task). The shorter focal ratios are not
suited to high powers, and planetary viewing.
3. Catadioptic telescope - These are combination mirror/lens
systems, the most popular being the Celestron line of Schmidt-
Cassegrain scopes. Before Celestron jacked their prices up
by a factor of two, one could buy an 8" scope for under $1500.
There are several varieties of catadioptic scopes:
A. Schmidt-cassegrain (Celestron & Meade) - most popular
B. Maksutov (Questar, Celestron C-90) - most expensive
C. Classical Cassegrain (Usually home-made)
Advantages: Their focal ratios (Schmidt-Cass) tend to be
around f10-f11, thus they are suitable for both lunar/planetary
and deep sky work. They are also highly portable, and are
much more stable on their mounts than either reflectors or
refractors.
Disadvantages: Their focal ratios still are not the best for
deep sky astrophotgraphy. Field size is a bit of a problem,
as with refractors.
As to which type you buy, you will have to decide for yourself, based
on what you think your observational needs will be. With more info
on your expectations and needs, I could possibly recommend one, though.
As for astrophotgraphy... I do not know what your experience level
is, so forgive me if I cover too much elementary ground. There are
roughly three different kinds of astrophotography you can do:
A. Lunar/planetary
B. Wide field (constellation)
C. Deep sky
All require a very sturdy, clock driven equatorial mount, with a
motorized declination shaft. Lunar and planetary photography can be
accomplished using your Pentax, and exposure times of roughly 1/500 s.
up to 10 sec. depending on the subject, focal ratio, and film speed.
Wide field photography can be accomplished with your Pentax by
piggy-backing it on your scope. Best results can be obtained by using
a 135 to 210 mm telephoto lens on your camera. Exposures can range
from 10 minutes to 30 minutes, so they will need to be guided. Also,
gas-hypered film will improve the results on star cloud photography.
Deep sky photography is perhaps the most difficult (er, challenging).
For this, you will need a special camera called a "cold camera" (because
it utilizes dry ice to keep the film at -100F). You will also need
a good dual-axis drive corrector, and an off-axis guider. These three
items alone will cost you a total of $500. Additionally, you will need
to process your own film, because the cold camera only holds one small
film "chip" at a time (roughly the size of a 35mm frame). Exposure
times are generally 60 minutes. This technique produces truly outstanding
astrophotos once mastered.
This reply is awfully long-winded, but I hope it helps. I didn't
talk about special purpose scopes, like Schmidt cameras, because I gather
you are "just starting out". Feel free to contact me for any further
advice/questions/whatnot.
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We've had a Celestron C-8 for several years and are very pleased with it.
It meets all of your requirements, although it may depend on exactly what you
mean by "portable"----it can be carried, but I wouldn't want to carry it
too far! Good luck!
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Your constraints leave little choice. Very portable says get a
catadioptric (folded, short-tube optics). Astrophotography says get a
good quality worm gear equatorial mounting. The telescopes that fit
this description are the Celestron Super C8 or the Meade 2080. These
are both reasonably good choices. There are other catadioptrics, but
the ones I know of are too expensive or on flimsy mountings.
You could mix and match mountings and optics to get something a little
better, but that would be out of your price range and may require some
assembly. In fact your price range may require you to shop around for
discounts or buy something used. If you do get something used, make
sure to take along someone familiar with that type of telescope to tell
you if it is in perfect working condition.
Note that the Super C8 has a worm gear drive, while the older C8
(non-Super) has spur gear drive (not quite as smooth operation, so is
less convenient for photography). However, the older Celestron tripods
(the kind with two side-by-side tubes for each leg, not the new
adjustable-height telescoping-tube legs) I have found to be more stable
than the new ones.
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About telescopes: $1K+ is a lot of money for simple
amatuer telescopes. For what you want to do, it is only just enough.
All the things you have described point to one telescope -
the Schmidt Cassegrain style "Celestron" telescopes.
the standard ones for people with money are:
Celestron C-8 Super Polaris Schmidt Cassegrain $785*
Celestron C-8 Super Schmidt Cassegrain $1030*
* N.Y. discount prices
They are VERY compact, and specifically designed for astrophotography.
They achieve a highly magnification though the
use of the Cassegrain focal system that bounces the light back and
forth several times, allowing the scope to be short, although very fat.
Their stands have a lot of mass, making them very steady.
In return for these features, Celestrons are expensive.
(I can't afford one). But if you have $1,000, that should be no
problem. Also, you want to make sure that you get a motor or "star"
drive, for tracking. This is essential for photography, since you
often have exposure times of several minutes or even hours.
An excellent source for telescopes is Edmund Scientific Co.
in New Jersey. They have a mail order catalog that is crammed full
of many brands. Their own (Edmund's) brand of Newtonians are rated
a "Best Buy" by Consumer Reports. Also check the Astronomy magazines.
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I've been looking at telescopes recently, with the same interests/
constraints. You're best bet seems to be a Schmidt-Cassegrain from
either Meade or Celestron. Judging by the ads in "Astronomy", the
basic price is about 800 for an 8" scope, but they aren't too clear
about what is/is not included. 1200 to 1300 is probably a closer
estimate for a full system with tripod, clock drive, camera mount, etc.
The Schmidt Cassegrains are very portable ( an 8" model is about 2 feet
long), and are very popular for astrophotography. I'd like to find
out what other people have to say on the subject. Good luck!
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Get a Questar: no doubt about it, the best that money can buy, and
worth the difference w.r.t. the inferior ones.
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I'm not absolutely sure I can post to this news group any more, so
just in case I can't, here's a comment on your question regarding
telescopes. A few years ago when I was editing a geophysical journal
and as a federal employee unable to take the honorarium in cash, I
bought a Questar, then $1250 or so for the 3.5 inch model. If the
small Questar is still within your price range, I suggest that you get
one, since it is far superior to any competitor in quality, ease of
use, and adaptability to photography. You also have the pleasure of
owning the Rolls-Royce of telescopes.
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In the small projects for the net.astro group. I suggested we put together a
buyer's guide. There is very little interest, but here is my summary of hoe
to do it. If you want to add anything. Please forward it back, so that
others may benefit from this 'network memory.'
ADVICE FOR TELESCOPE PURCHASERS
E. N. Miya
and others on the net
[add your name and we'll integrate it
it somehow, don't worry]
SO YOU WANT TO BUY A TELESCOPE
Avoid impulsive buys. Don't, unless you really have to [e.g., astro
photography, is an exciting, but non-trivial hobby.]
If you just want to look at stars,
planets, nebula, or Halley's Comet, looking through a local planetarium's
or community college's [university's] telescope will probably be far better,
and you won't have something collecting dust after a while.
Realize that the Andromedia Nebula (M31) will never appear to the naked eye
as it appears in photographs taken over hours of exposure.
TRY DIFFERENT TELESCOPES
There are companies which rent telescopes (in large cities) or can
provide demos for universities. Ask around your area. Join amateur
associations.
TYPES OF TELESCOPES
REFRACTORS
REFLECTORS (aka Newtonian)
COMPOUND SYSTEMS
Questars and Celestrons fall into these areas.
SELECTING AN OPTICAL SYSTEM
You need to ask yourself, what are your reasons for purchasing the telescope.
For purposes of net.astro, we will assume astronomy.
The first (and less important) thing first time telescope buyers consider
is magnification "power." Without detailing all the reasons, the single
most important factor in purchasing a good telescope is light gathering
power. Get a telescope with as wide an aperature as possible.
Check for defects: bubbles in refractor optics on cheap telescopes are
not uncommon.
Another set of important considerations are the mount-types and clock drive.
It's difficult to see any image without a stable viewing platform. Fixed,
sheltered piers are best. Tripods are systems of last resort.
Eye pieces are an important set of accessories.
TESTING AN OPTICAL SYSTEM
You can make some simple optical tests to be viewed at a distance to
see problems such as spherical and chromatic aberrations.
LEARN HOW TO LOOK THRU AN ASTRONOMICAL TELESCOPE
[discussion on cones and rods in the eye and peripheral viewing.]
LONG TERM TELESCOPE CARE
Reflector systems should be occasionally re-silvered.
REFERENCES
For instance [I have few astro books in my office (they are at home)]:
%T Amateur Telescope Making, Vol. I, II, III
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May I recommend that you look into a Vega Moksitof (sp) Cassigrain.
Vega is the brand name MC is the type. Somethin about six inches will
get to a lot of objects. You'll want an equitorial
motor driven mount, a 24 volt battery, a motorized back for your
camera, and a WWV time sync reciever and controller to control your shutter.
Buying new with the $s available may be hard. Look in SKY and
TELESCOPE for a used Vega. Have fun.
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