Any benefits of using a 2" diagonal with 1 1/'4 eypieces (w/adapter)

[mlb585]

This is my first post here so be gentle. =) I currently own a Celestron CPC 800 and only use 1 ¼ eyepieces. I was going to upgrade my diagonal to a Televue Everbrite, William Optics or Orion model and I was pondering where or not I should get a 2” diagonal w/ 1 ¼ adapter instead of a 1 ¼ diagonal. In the future I may go to 2” eyepieces but for now I am sticking to the 1 ¼. Is there any real benefit of using a 2” diagonal (w/adapter) when only using 1 ¼ eyepieces? I didn’t know if there was really going to be any other benefit other than the ability to go to 2” eyepiece in the future. Does using a sizing adapter cause any issues in the future with filters or any other add ons like barlows? Thanks in advance for your help!

[Peter Drew]

A 2" format could be beneficial fo photographic purposes assuming you needed to use the diagonal for some reason. As far as eyepieces are concerned, if the field stop is less than the aperture through the diagonal then there is no advantage with the larger unit. The 2" diagonal should come with a 2"-1.25" adaptor so you could have the best of both worlds.

[mlb585]

I just realized that I would have to get a 2" visual back for the SCT scope as well if I want to go with a 2" diagonal. It sounds like unless I am really going to 2" eyepieces soon, maybe the 1.25 diagonal would be the best fit (and less expensive). Does anyone think the benefits outweigh the costs when going to 2" eyepieces (for mostly viewing and some light astrophotography)?

[John]

If you are going to upgrade you might as well go to 2". I use 2" digaonals with my scopes and have a mix of 1.25" and 2" eyepieces. When you do consider filters 2" is the way to go as well so that you can use them with the larger format eyepieces, when you get them. You can use a 1.25" barlow like the Celestron Ultima in the 2" diagonal - I think they are designed to be used that way.

[alfingido]

I just realized that I would have to get a 2" visual back for the SCT scope as well if I want to go with a 2" diagonal. It sounds like unless I am really going to 2" eyepieces soon, maybe the 1.25 diagonal would be the best fit (and less expensive). Does anyone think the benefits outweigh the costs when going to 2" eyepieces (for mostly viewing and some light astrophotography)?

You wont need a 2" visual back for a 2" diagonal if you get one with an SCT fitting. It will screw directly to the rear cell.

If you specifically need the 2" visual back, then you can get one and a push fit diagonal, but you will increase the weight on the rear cell.

You may well find you want some 2" ep's in the future, you may as well get the 2" diagonal. They look pretty impressive too!

Allan

[brantuk]

Hi mlb - I just upgraded to a 2" diagonal (with rear cell fitting) to take 2" ep's. It came with a converter so I can still use my 1.25" 's as well.

I specifically did this to accommodate binoviewers and maximise light gathering.

I'll be trying out some recently purchased 2" ep's (40,30,12mm) as soon as the weather clears with both my scopes. I'll let you know how I get on with the cpc.

Cheers

[ollypenrice]

As soon as I read that you were using an SCT I knew I'd be recommending 2 inch. You have a long focal length and are, therefore, very 'boxed in' in terms of field of view. To see wide, and there is so much to enjoy that way, you will need 2 inch EPs. I have a 35mm TeleVue Panoptic which is adorable. An expensive 1.25 diagonal would not be a good investment in my book.

Olly