…continuedChoosing Your First Telescope
Kicking the Tires
You can't test a telescope's optical performance properly in a store, and many of the best telescopes are sold by mail order anyway. So you should ask the vendor to spell out return policies (preferably in writing). Make sure you'll be given enough time to try a scope out under the stars and the opportunity to return it for a refund. (If you buy the telescope mail order, expect to pay for shipping if you return it. In addition, being asked to pay a "restocking fee" is only fair if you want the privilege of being able to test-drive and return a telescope that's not actually broken.)
Once you get the telescope, new or used, scrutinize everything about it in daylight. The mount should be stable enough to remain standing even if someone bumps into it in the dark. Give the scope a gentle tap while viewing some distant target. Does the view jump around only a little, then stabilize? Good! But if it hops around for several seconds or more or if the view moves so much when you hold the focus knob that you can't focus well it'll be endlessly frustrating. Finally, you should be able to move the telescope easily and smoothly (whether by pushing the telescope's tube, turning a knob, or switching on an electric motor) without jerkiness or a backlash problem.
Assessing the telescope's optical performance is harder for a newcomer to visual astronomy. But even an inexpensive telescope should pass the following nighttime tests.
Point the scope at a starry region in or near the Milky Way. Use a fairly low-power eyepiece. Stars at the center of the view should focus to points without any flares or colored halos. (Flares or halos may appear at the edge of the field of view, but they shouldn't be prominent until at least halfway out.)
Now get aimed at a fairly bright star and switch to high power. Focus the star, then turn the focus knob just a little one way, then the other way. The out-of-focus images that you see when you turn the knob one way, then the other, should be nearly alike. This is a strict test; rare is the telescope that passes it perfectly. But if the either-side-of-focus images are quite obviously different from each other, the optics are poor and the views will never be as sharp as they should be. (Eyeglass wearers with astigmatism should keep their glasses on for these tests.)
Finally, examine the Moon: it should look crisp, not hazy, and it shouldn't produce distracting ghost images (the result of inadequate coatings somewhere in the optics).
Keep in mind that perfection is expensive, and that a lot can be seen with less-than-perfect equipment. (It's the only kind I've ever owned!) Be patient with your new telescope and with yourself. At the same time, don't be afraid to ask for help! As time goes on, the wonders of the heavens will become familiar friends.