Meade lx65 8" (ACF) vs Celestron 8se

[HappySkeptic]

We are thinking about getting a telescope again. I've pretty much got it narrowed down to either a Meade lx65 8 ACF or a Celestron 8se. Anyone with experience with both have a preference one way or the other? I'm leaning towards the Meade because of the Advanced Coma-Free (ACF) catadioptric-variant optical path.

Here is a good discussion about them Cloudy Nights

I'm not an expert on either of these, but yes I would go for the ACF.  Celestron has their Evolution HD or Edge HD, but they are more expensive (but I understand that they are very good!)

For the price, I would go with the Meade.  If you are willing to pay more, you have more options.

Also realize that you are going to need eyepieces, and good ones are expensive. Also, consider what you are going to do about dew (heaters, tube extension, 12V hair dryer).

BTW, I've never owned a catadioptric telescope. I currently own a large refractor and a large Dobsonian.

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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.

Thank you for taking the time to write the book. I really do appreciate it.

I already understood some of what you wrote like how to calculate magnification. Even the part about to much magnification being a bad thing. What I don't understand is how that applies to real world viewing. For example what is too much for one of these scopes for different objects the moon, Saturn, Jupiter, and Andromeda?

As far as photography goes I have a decent FX format Nikon, but I was also looking at one of the Celestron 5MP imagers. I think they are limited to like a 30 second exposure though so I'm not sure which way I want to go yet.

I was also looking at one of the Celestron Eyepiece and filter kits. They run about $170 retail and come with:

32mm Plossl Eyepiece - 1.25”
17mm Plossl Eyepiece - 1.25”
13mm Plossl Eyepiece - 1.25”
8mm Plossl Eyepiece - 1.25”
6mm Plossl Eyepiece - 1.25”
2X Barlow Lens - 1.25”
#80A Blue Filter - 1.25”
#58 Green Filter - 1.25”
#56 Light Green Filter - 1.25”
#25 Red Filter - 1.25”
#21 Orange Filter - 1.25”
#12 Yellow Filter - 1.25”
Moon Filter - 1.25”

on top of the eyepieces that come with the telescopes. From what you said I'll probably want to upgrade later, but I'm hoping that will be enough to get us started.

If you stay with the hobby, you will probably sell that eyepiece kit and get something better.  You might want to go into an astronomy shop and ask about eyepieces.

Honestly, you only need 3 eyepieces to start.  A 30mm to 40mm for low power.  Then something in the 17-22mm range for medium power.  Then something smaller like 10 or 13 for planets and perhaps globular clusters.  You will use the low-power when finding object, and then bump up to the medium power to do most observations. 

A planetary eyepiece is really only good for planets and sometimes a tight globular or planetary nebula.  You could use even more magnification on planets -- like that 6 or 8mm, but most nights it will just look like a fuzzy mess because of atmospheric seeing (or your telescope not being cooled down yet).

Eyepieces come with different apparent field of view (AFOV).  This is where the expense comes in.  Wide AFOV eyepieces let you see more of the sky at the same magnification.  I am an AFOV junkie, but my eyepiece collection costs a few ounces of gold.  Large AFOV can be a bad thing if the eyepiece is an old cheap design.  You will probably want to go with something in the 55 to 70 degree range.  Smaller is just too small.  Larger and good quality may cost too much (unless you limit yourself to just a few eyepieces).

Some colored filters can help with planetary detail, but if they are poor quality, they will be useless.  These filters serve no other purpose (well, a moon filter can be useful, but I've never bothered).  I wouldn't bother with them.

Here is some telescope math.

Exit-Pupil = eyepiece-focal-length / f-ratio.  Your f-ratio is 10.  So,

Exit-Pupil = eyepiece-focal-length / 10
Eyepiece-Focal-Length = 10 * Exit-Pupil


Low Power Exit Pupil = 3.5 -> 6 mm .   That means 35 to 60 mm eyepiece.  In reality, choose 30 to 40.  Anything that has a large field-stop and is over 30 mm is good.

Medium Power Exit Pupil = 1.8 -> 3.5 mm.  That means 18 to 35 mm eyepiece.

High Power Exit Pupil = 0.5 to 1.8 mm .  That means 5 to 18 mm eyepiece.  Something like 5 to 8mm is only for planets. Really, 5 is too high a power on anything but the best optics with excellent nights of seeing.  A compromise of 10 to 13 mm might be slightly low for planets but still nice, but could be useful on some star clusters.

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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.

If you haven't done astronomy before, I would join a local astronomy club, or go a star party (wrong time of year for that, though).  Most new telescopes don't get used more than a few times, because the owners can't find anything in the sky, or the telescope doesn't give them the views they hoped for.

These are fine entry-level scopes.  You should be able to see a lot with them.  But I hope you have realistic expectations, and want to explore.  These can connect you to the universe when you get to know what is up there.