New eyepiece or new telescope for wider FOV ?

[Captain Harlock]

So I have nearly managed to save enough for a C8 CGT, and if all goes to plan I should pull the trigger by the end of this month.

I currently have 3 EPs I like a lot : SW Nirvana 7mm, 16mm and 28mm.

However, even with the 82deg FOV of the 28mm, I should have a rather restricted FOV because of the relatively long focal length of the C8.

I was planning to get a good EP for wide FOV (about 40mm).

The thing is, a relatively good quality one costs at least £280, which is pretty much more than a SW 8" Newtonian.

Even on the 2nd hand market, it would be cheaper to buy a Newtonian telescope than a 2" 40mm EP.

It looks like getting an Explorer 200p would give me much more flexibility and options than a 40mm EP.

My mount is a Giro Ercole, so I would even be able to mount both scopes side by side.

Am I missing something, or is it really a no-brainer ?

Many thanks,

Hugo.

[Captain Harlock]

Sorry for the typo, I meant SCT not CGT 

[nicoscy]

At 40mm the only eyepiece with a 1.25" format is the venerable Plossl with 43 degrees AFOV.

Swap the visual back for a 2" visual back and diagonal and you can use eyepieces yielding up to about 1.4 degrees TFOV, like this:

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p2333_TS-PARAGON-ED-40mm-2--Superweitwinkel---68-Grad---6linsig.html

This eyepiece gives you a low 50x magnification and a nice 4mm exit pupil. Price with shipping should be EUR 160 = GBP125 and at your scope's f10 focal ration should perform like a champ!

And to save you some money: If you use a focal reducer, this increases the aberrations of the eyepieces and at 1.25" gives you the same benefit as going to 2" visual back. If you stick the reducer with a 2" back you will have severe vignetting so best to avoid.

And you are not missing something. It depends on the objects you want to view. I would generally go with an 8" Newt over an 8" Cassegrain and enjoy twice the field and newts can handle magnification quite well. Of course you have to know to collimate but that is fairly easy to do. 

But the SCT has a smaller footprint so again, it depends on how much space you have for storage, what objects you view, how wide do you want the FOV to be e.t.c...

[Moonshane]

my approach is the same as yours. it's cheaper to buy a second / additional scope than a wider field eyepiece.

[John]

Even with a 40mm or 50mm eyepiece you won't see much more sky with the C8 than the 28mm Nirvana will show. It's just not a wide field scope. As Shane suggests an 8" F/5 newtonian tube would cost less (used) than another big wide field eyepiece and would show you twice as much sky as the 8" SCT does.