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Backyard Astronomy
Telescope Astronomy
In the old west, choosing a town marshal was picking a bad guy you could
live with who'd get rid of the bad guys you couldn't live with. Selecting a
telescope is about the same process. All telescopes have advantages and
disadvantages, but - and this is the point - they all have disadvantages.
Choosing your first scope involves finding one that has disadvantages you can
live with, but none of the disadvantages you can't live with.
The most important advice I can give you is, if you're totally to telescope
astronomy, find a local astronomy club in your area and attend one of their
public star parties. Here, you'll have the chance to look through various kinds
of telescopes and ask questions of their owners. The value of the advice you'll
get from such star-parties is incalculable.
The following are the major issues you'll be facing:
 | Usability - Above all remember that all telescopes in a closet work
exactly the same. The best telescope is the one you'll actually use. |
| Aperture - the refers to the overall diameter of the telescopes.
Some will tout "Aperture Rules" - the bigger front-end, the better - but if the scope's so heavy or cumbersome
that you're hesitant to take the time to set it up, it's not the scope for
you. Aperture is important - very important - but not at the cost of
everything else. The disadvantage is, the larger the telescope, the heavier it
is and the more difficult it is to transport and set up. |
| Optics - You have, basically, three choices: refractor, cassegrain,
and reflector. Refractors give very sharp images, but per inch of aperture are
quite expensive. Cassegrain telescopes are less expensive than refractors, but
have more reflection surfaces, which tend to scatter the light. Reflectors are
the least expensive, per inch of aperture, but they require frequent
collimation (mirror alignment) and, compared to cassegrains, are fairly bulky. |
| Mount - There are two kinds - altitude/azimuth (abbr. "alt-az") and
equatorial. Alt-az means you have control over the scope in altitude
(up/down) and azimuth (left/right). Equatorial, on the other hand, requires
the center-post of the mount point to the North Star. Equatorial mounts are
better for manual tracking, but setting up an alt-az is
much easier than setting up an equatorial mount. |
| Electronics - This refers to the selection, acquisition and
tracking of a 'target'. The simplest is no electronics whatsoever
(manual), whereby you acquire the target, and track it, yourself. No
batteries, no cords, nothing. The next level is "push-to", which has a
computerized object locator. You select your target (through a 'handbox') and
you push the scope until the alt/az difference is zero. You still have to
track the object yourself, though. Then there is 'Go To', and with this you
select an object through the handbox (or, in some cases, a connected computer)
and the scope finds the target and tracks it for you. Obviously, the more the
telescope does for you, the more expensive it gets - but the easier it is to
use. But you also need power (or a lot of batteries), which also means less
attractive transport issues. |
| Accessories - It doesn't stop at buying a scope. In your decision
for that purpose, include the accessories you'll be needing. These are such
things as eyepieces, diagonals, red-dot finders, and so on, and so on. With
most folks, by the time they're done, they will have spent as much on
accessories as on the base telescope. You might think this is equal across the
board, but it's not. Here's an example: A "slow" (f/10 or higher) has a flat
visual field compared to "fast" (f/6 or lower) scopes, which means the slow scopes
don't need the expensive eyepieces that fast scopes do. |
| Visual-Only or Astrophotography? - If you are thinking about
astrophotography, let me just say, get out your wallet. Telescopes for
astrophotography need better optics, better tracking, heftier (expensive)
mounts, and more accessories
than do those designed for visual-only. The point is, don't buy
astrophotography
features you won't (can't) use if you're visual-only. |
This is not an easy decision. And, as I stated above, your best advice comes
from actual viewing through a scope at a star party, or a neighbor's scope, or a
store scope or something - anything. The more you know about scope operation and
what kind of image to expect, the more successful you'll be in selecting one
you'll actually use. The less you know about these things, the odds against you
stack up pretty quickly.
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