Just bought a new 5’’ Meade telescope. When setting up during cold nights is it necessary to let this instrument adjust to the ambient temperature to get sharper images and if so how long does it take? To all you astronomy experts, HELP!!!
How long cooldown takes depends on the type of scope you have, the temperature it’s stored at, and how cold it is outside.
You don’t say specifically what type of scope you have, but from what you’ve said I’m going to assume it’s one of the shorter enclosed types like a Schmidt or Maksutov as opposed to a large truss-based scope like a Dobsonian. The type you have can take a long time to cool down. If you’ve got a Maksutov, depending on if you keep it inside the house or in a cool garage, you might be looking at 90+ minutes for cooldown.
Lighter scopes with thinner mirrors take less time. If I had to throw out a number, I’d say minimum of an hour, but like I said, there’s a lot of factors that go into that number.
I think the best way to figure things out is to just use your scope. Start with a 60 minute cooldown, then pay attention when you’re using it. Does the image seem to suddenly get clearer after you use it for 20 minutes? Then maybe it needs longer to cool down. If you don’t see any difference depending on how long you use it, then you’re letting it cool down enough.
Ditto Athena. You can also do things to have your telescope better prepared. If there is some way to store it or hold it a little while in an environment at the temperature you expect to observe in, that helps.
You can also comprehend what is happening much better if you put in a high powered or short focal length eyepiece, aim at a bery bright star, and adjust the focus way wrong to turn the star into a disk (which will probably have a hole in the middle). This disk is an image of your telescope system, painted with that one star’s light. You will probably see vivid waves circulating around. If you hold your hand in front of the telescope you should see a perfectly clear sillhouette of your hand, with waves of heat rising from it. This will all look different if you are aiming straight up versus near the horizon. Anyway, it is these waves that are making your viewing a little blurry when the telescope is at the wrong temperature, and this method lets you view the problem more clearly to understand it better.
“bery bright star” is a highly technical term involving quantum field theory, and if you aren’t into higher math, there’s no way you are going to get this one.
That being said, if you substitute a “very bright star”, the method will also work.