Source: Tom's Guide US | Keywords: celestron, telescope | Themes: Digital Cameras, Digital Entertainment
2. Common Telescope Types
For those new to astronomy, there are three main types of telescopes, and I have compiled a brief chart of the relative advantages and disadvantages of each. From Starizona website , I copied internal diagrams of each type. There’s a good article on choosing a telescope at Sky and Telescope’s website and from Stellafane website. Or check out Hack #9 in Astronomy Hacksfrom O’Reilly website. Other Internet articles on this topic also abound.
Cut-away diagram of a standard refractor.
Cut-away diagram of a standard reflector, sometimes called a Newtonian reflector.
Cut-away diagram of a Schmidt-Cassegrain (SCT), also called a catadioptric, for its combination of a lens and a mirror.
| Property | Newtonian Reflector | Refractor | Scmidt-Cassegrain |
|---|---|---|---|
| Cost - per aperture | Least expensive for given size aperture | Most expensive for given size aperture | intermediate |
| Size, portability | Length 8X mirror diameter | Very long, unwieldy for given aperture; eyepiece at inconvenient location | Very compact; length is 2-3X diameter; one person can easily transport, set up to 12” |
| Astrophotography | Equatorial mount required for DSO objects; Dobsonians generally not suited | Equatorial mount required for DSO objects; Dobsonians generally not suited | Very good; mirror shift may make focusing difficult for some accessories |
| Deep Sky Object (DSO)Viewing | Good to very good; a bigger scope is less expensive | Pristine image, but size limits aperture, a problem for faint DSOs | Generally good |
| Planetary Object viewing | Slightly degraded because of secondary mirror spider | Best; want apochromatic, but very expensive | Slightly degraded because of center obstruction |
| Temperature Equilibration Time | Generally fast; very large ones cool slowly | Small ones are fast | Intermediate, depends on size; dew shield and fan for larger scopes |
| General | Must be collimated, but easy to do; may require occasional cleaning | Sharpest, higher contrast; more rugged | General purpose viewing; lightest; retains collimation for long periods; viewing done from seated position |
There are variations on the scope types mentioned above, such as another type of folded optic design called Maksutov-Cassegrain. There are also hybrids of Maksutovs, SCT types, and reflectors. A true Maksutov has a thicker corrector plate, so it requires more cool down time, and usually isn’t used in larger scopes. One very popular type of scope is named for its inventor, Dobson, and refers to its mount. This scope is a standard reflector, but mounted on a flat base, which makes Dobsonian scopes inexpensive. But the Dobsonian’s alt-az base, and the difficulty in mounting a precise drive, makes astrophotography all but impractical. Yet the Dobsonian mount led to a revolution in affordable astronomy, whereby amateurs began making large telescopes-from 10” to a whopping 22” in diameter.
- Previous page Celestron NexStar 6SE
- Next page Telescope Mounts
Many amateurs started by using a GoTo. IMHO, the more astronomers the better. Talking to denizens of LAAS and reading cloudyskies.com, there is little sense of elitism. All amateurs are welcome, even and esp. those with GoTos.
I didn't have room to talk about the wedges that covert yoke mounts to equatorial mounts, but they exist for many yoke types. That way you can have the best of both worlds.
Finally, one of the books I recommended does just what you suggest: tries to teach the night sky so you can find stuff without using (or even using) a GoTo. Hope this addresses your comments.
Doug
The fact is that these new generations of scopes make astronomy so much more accessible to people who find astronomy interesting but don't have the time or ability to invest. They also make it simple to introduce new people to astronomy by quickly showing them lots of interesting things.
Plus, as a computer geek, there is nothing more fun than plugging your telescope into your laptop, hooking up a camera and driving it around from your computer. Do an easy DIY project like adapting a webcam to use with the scope and you have yourself tons of fun *and* you learn the night sky, you just don't waste months of time trying to figure out how to see anything.
I really praise the point of your article. I also love to teach everything I know about the topic to anyone who's interested in the subject, like most amateurs.
Like you said, there's no to little sense of elitism in those groups. But I also know this: Like all the really rewarding things in life, Astronomy requires persistence and solid interest.
I decided to comment your article since I disagree on some things you wrote and that contrast may help people who read it, look at the picture from another angle.
Trying to find Deep Sky Objects or the planets (very easy with little experience and knowledge) in the sky, is where most of the fun is! Having a computer doing it for you is like you own a Porsche and let a chauffeur drive you. The only difference here is that, unlike the chauffeur, the computer has no fun at all!
I didn't find anything interesting on cloudyskies.com, apparently is just a domain for sale. Did you mean www.cloudynights.com?
If your interest is solid, you've got nothing to fear, understanding the sky is a lot easier than most people think.
Diogo.
My bad! Yes of course I meant www.cloudynights.com. It's a great site for advice, and mostly cogent tips on purchasing and use.
I think we can agree that for some, starting with GoTos is a great way of getting into astronomy. Then you can progress to star charts and maps, relying less on the GoTo. I want to encourage people to begin this exciting hobby.
Amateur astronomers are one of the few science disciplines where amatuers can and do make professional level contributions!
And even though I understand how the SkyScout works, it is unbelievable to actually use it and watch it ID an object, or have it guide you to some random star in its database...Awesome product. For me, this really helped me better learn the night sky. It's like using a crutch (or a chaffeur) then weaning yourself away from it and driving yourself. Much less pain, and kick butt fun.
Hope this answers your concerns.
Clear skies!
Doug
I am a beginner in the field of astronomy and astrophotography and I would like to purchase some equiptment. Im not exactly sure what types of telescopes and astrophotography equiptment would be best for a beginner and it would be great if you could offer me some advice. I have done a lot of research on telescopes preferably under $500 and CCD cameras along with laptops. If you have any advice that would be great! Thanks.