It's been discussed before, but...

[revbarryb]

Just ordered my first goto SCT (C8SE). After LOTS of reading here and elsewhere, I'm STILL not sure whether to get .63 focal reducer/corrector,  or a more expensive 2 inch star diagonal. Leaning towards the fr/c... but I have some NICE 2 inch eyepieces. I fully admit that I don't fully understand all the optical physics I've read in these discussions... and it seems there are knowledgeable folks advocating both ways for sharp visual observing. I own an 8 inch dob, a 5 inch Newtonian, and a 4 inch Televue apo frac (where the 2 inch eyepieces really shine) ... but the goto 8 inch has long been a dream. So not to put too fine a point in it,  how do I get the MOST out of it?  Thanx in advance for any replies!

[PXR5]

My theory is if you already have the 2"ers then go that route.

 

(As you probably already know, 2"ers don't play well with the FR/C)

 

I had sold all my 2"ers by the time I got my C8 so I went with the FR/C. 

The only disadvantage is the 2" EPs will add more weight to the set up.

 

Edited July 27, 2022 by PXR5
Speling

[Louis D]

Unless you're strictly using the TV APO straight through, you already have a 2" diagonal, so I don't understand the comment about buying a 2" diagonal.  They don't have to be expensive, though, if you want to keep one with the SCT.  I picked up 3 used GSO 2" 99% dielectric diagonals from Cloudy Nights classifieds to keep with various scopes for about $70 each.

You will need a 2" visual back if the SCT doesn't come with one.  They're about $25 to $35.

I would try the 2" eyepieces because there are some fine 2"ers at shorter focal lengths as well the longer widest field ones.  The 12mm and 17mm ES-92s are two I can think of right off the bat.  The 21mm Ethos also comes to mind.

[revbarryb]

Thanks for the input.  I did wonder about trying the TV diagonal on the 8SE. And yeah, still need the appropriate visual back. Some of what I read mentions that the 2" diagonal may prevent pointing the scope near the zenith. But it's worth a try... and just sliding the OTA a bit more fisted fwd in the mount.  I know it'll be a learning process! I currently have a 2" 15 Nagler, a 32 Erfle, and a 40 widefield

[Cosmic Geoff]

 

5 hours ago, revbarryb said:

and just sliding the OTA a bit more fisted fwd in the mount. 

You should slide the OTA as far forward in the clamp as it will go anyway.

I am a sceptic as regards using the f6.3 focal reducer and 2" eyepieces with the C8 SE in a visual role. You will note that I have one...

The focal reducer is really intended for imaging, in which role it excels. If you want to buy a 2" visual back, 2" diagonal and use your 2" eyepieces to get a wider field of view that's up to you.  But you already own wider field instruments, so why bother?

I very rarely use my telescopes in a visual wide field role.

[Louis D]

3 hours ago, Cosmic Geoff said:

I very rarely use my telescopes in a visual wide field role.

Because a lot of big, heavy eyepieces are 2" only as I pointed out above.  For instance, all of the ES-100 and ES-92 eyepieces are 2" only.