2 inch or 1.25 diagonal

[Steve Clay]

I've collected my ED80 and its a cracker. It's the outfit so has the 2 inch dialectic diagonal. However, all my EP's are 1.25. It's got the adapter. My questions are: 

Will it be better to use the 2 inch diagonal with my 1.25 EPs

Get a descent 1.25 diagonal for use with my ep's

Or does it not matter either way.

I can't really stretch to new 2in EPs

Cheers

Steve

 

[RT65CB-SWL]

I prefer to use a 2" star diagonal than a 1.25" with my 're-modded' ETX105.

Edited November 23, 2019 by Philip R

[johninderby]

Doesn’t really matter. The 1.25” is lighter and has a shorter light path than the 2”. 

With an ED80 though would just use the 2” that you have.

Edited November 23, 2019 by johninderby

[cloudsweeper]

All my 'scopes have 2" diagonals, and all EPs are 2" or have semi-permanent self-centring adaptors.  I just find it easier to be able change all the EPs over this way.  Why 2" EPs? - wider field at lower powers.

Doug.

[Alfian]

If using a 2" diagonal, with 1.25" adapter, doesn't create any issues (balance?) then  there is no reason not to use it. Personally I've found on 'scopes used in the past that having a 2" diagonal to use just one "lower power"EP to give wide field views, when the rest of my EPs are 1.25" is a lot of extra weight for just one eyepiece. I now find that a 1 .25" diagonal and EPs is adequate for my particular setups. 

[ScouseSpaceCadet]

The diagonal you have is a sturdy dielectric with a compression ring to hold eyepieces. I use an ED80 diagonal (it was going very cheap and I was looking for a dielectric) with my Startravel 120 scope, the views are great, the eyepieces are secure and not marked by screws. It looks nice as well...

Unless you're trying to shave a few grams in weight off the setup, there's no reason to change it. Also it gives you the option to try a 2" widefield EP in the future.

 

 

Edited November 23, 2019 by ScouseSpaceCadet

[johninderby]

The Skwatcher dielectric 2” diagonal isn’t the best but still a reasonable performer. A WO or a Revaltion quartz will nave a bit more contrast though. 

[wookie1965]

I use a Altair dielectric diagonal in my Meade which was used in my Tal I have bought a 1.25mm for the Tal not had chance try it with this weather but have checked collimation with a laser.

I still want a good 2" diagonal for the Meade and put the Altair back in the Tal.

I have been looking on the second hand market but not come across one at a good price yet.

just having to buy a battery for the car £78 going have wait until after Christmas now.

[John]

As you have a decent 2 inch diagonal you might as well use it. You never know, you might come across a half decent 2 inch eyepiece at a bargain price sometime and want to see what those wider vistas look like. A good quality 1.25" diagonal will probably cost you £50 and that would get you a nice used Aero ED 2 inch eyepiece

 

[joe aguiar]

Agree with all since it came with it use it.

That's what I do on all my scopes have 2 inch diagonal. 

Joejaguar 

[Louis D]

On a refractor, it doesn't matter much which size you use so long as the front of the focuser tube doesn't have to be racked in so far that it starts to cut off part of the light cone.  Aside from using a binoviewer with a really long focuser tube, this usually is not an issue.

On catadioptric telescopes that focus by moving the mirror, the smaller ones are often designed to work best with the optical path length of a 1.25" diagonal, and moving the mirror to accommodate the additional path length of a 2" diagonal can add some minor spherical aberration in SCTs and possibly something similar in Maks.