Meade lx65 8" (ACF) vs Celestron 8se

[polymath257]

Another question is what you intend to use your scope to do. The focal length on these points to looking at small objects like planets or planetary nebula as opposed to galaxies or the broader nebula like Orion or Eagle. Make sure this is what you want from your scope.

I was looking at these two because they were the biggest mirrors in my price range. The thought process there was more light = more desirable. I wanted to us it for both planets and larger objects, but this sounds like neither of these are good solution for that.

Yes, larger objective=better is true all other things being equal. But there are trade offs. The larger focal length will produce higher magnification for a given lens. This has good aspects and bad aspect.

Planets and planetary nebula are small in angular size. Close by galaxies, like most of those in the Messier catalog, tend to be *large* in angular size. But, while planets tend to be pretty bright, galaxies tend to be dim and 'cloudlike'.

If you magnify a planet, you get a larger image which *often* means you see more detail (see below). if you magnify a galaxy, you get a larger area of haziness that s just as dim. If the galaxy in question is already large (like Andromeda or the Whirlpool), this is NOT an advantage. You will generally see more at lower magnifications, which have a wider field of view.

Next, magnification has its own issues. The problem is that we look through an atmosphere and that atmosphere often has a lot of turbulence in it. This is known as 'seeing'. A high magnification only magnifies that turbulence and you don't actually get to see more.

In general, don't expect to use a magnification above 350x except *very* rarely. The seeing just usually doesn't allow such to be useful. Oh, but when it does!

When I go out to observe, I generally stay in the 100x to 200x range of magnification, only pushing above that if the conditions are excellent.

In practice, this means that, unless you have been to a star party and seen what a telescope can do, you are likely to be disappointed at first in your views of planets. Jupiter is easy and fun. Saturn's rings are easy. But getting details in the clouds of Jupiter takes very good seeing. Seeing the Cassinni division in Saturn's rings is usually going to be possible, but don't expect detail in the clouds of Saturn.

Mars is HARD. Period. You can see a polar cap and maybe some vague dark markings. Don't expect anything else. Even in professional telescopes, it is hard.

Next, are you planning to do photography? if so, make sure your mount is absolutely stable and you have a quality camera that can take time exposures. Without photography you are very unlikely to get many colors from nebulae (other than a blue-green). i was able to see color in the Orion nebula using a 'yard scope' (36" mirror), but that was what it takes visually.

Finally, and this is a*very* important, what are you spending on your lenses? I would plan to spend as much on them as the scope itself. The wider the field of view, the better (but you will pay for 82 degrees!). Don't do anything under a Plossl. Get a variety of sizes and watch what the magnification will be from each.

To find magnification from a lens, take the focal length of your scope (2300 in the cases you are considering) and divide it by the focal length of the eyepiece. So, if you have a 25mm eyepiece, and a 2300mm focal length, the magnification will be 2300/25=92x.

Eyepieces below 5mm are usually difficult to use: they are narrow. A *very* high quality eyepiece can overcome this to some extent by having a wider field of view. Expect to pay for this luxury.

Sorry to make this a book. There are a lot of variable and beginners make a lot of mistakes. If you can (and I know COVID may not allow this), find a star party and look through some scopes. That is the best way to find out what is possible and what you want to see.