diagonals 1.25" vs 2"...

[Fozzie]

Afternoon everyone..

I'm sure I've seen a comment on a review of diagonals that stated the smaller format could cause interference with wide field EP'S by introducing a field stop in the focal pathway....

Have I just made this up or is there any truth in the matter that i could restrict the use of say my ES82 EP's in terms of fov by not having a 2" diagonal?

Ta

Fozzie

[CodnorPaul]

If you are using 1.25" EPs then I don't see how it could as the barrel of the EP will be in the way anyway - I would recommend 2" diagonal/EPs though, much more solid feel and take advantage of with wider FOV

[Fozzie]

Yeah thats what i thought.... but im frantically trying to find the review, to prove to myself im not going bonkers..... i fear that it maybe too late though!

[Moonshane]

the main issue is that any gnarly bits on a mirror are always at the edges and if you are close to the edge of your 1.25 diagonal with say a 24mm 68 degree eyepiece than you'd be better with a 2" diagonal. that said whether you'd see the difference I am not sure. there are other things to consider - balance, weight, size, cost, build quality etc but you cannot lose either way really with a decent brand.

[cutepetgroomer]

Myself, I'm planning on getting a hybrid diagonal . I do have an adapter that fits into the current diagonal.. But I do believe. Hybrid will have a better advantage.

[John]

The William Optics 1.25" diagonals and clones (of which there are a few) have a thick collar holding the 1.25" eyepiece tube onto the body of the diagonal. This collar causes a light loss at the edges of the field of view in eyepieces with wide field stops, eg: 32mm plossl, 24mm wide angle etc.

[Fozzie]

The William Optics 1.25" diagonals and clones (of which there are a few) have a thick collar holding the 1.25" eyepiece tube onto the body of the diagonal. This collar causes a light loss at the edges of the field of view in eyepieces with wide field stops, eg: 32mm plossl, 24mm wide angle etc.

That's almost word for word what I remember reading, it was a WO product they were talking about...

so it would impact my low power EP's more....?

[Dave In Vermont]

Although written regarding SCT's and the reason to upgrade to a full 2" visual-back, you may be able to get some good insights from this:

http://www.petersonengineering.com/sky/EO.htm

Clear & Wide Skies,

Dave

[John]

That's almost word for word what I remember reading, it was a WO product they were talking about...

so it would impact my low power EP's more....?

Yes, if the eyepiece has a field stop wider than the collar in the diagonal then those will be affected. Looking at your eyepieces I'd say it's a possibility with the 32mm plossl, and the ES 18mm 82 degrees (if it's a 1.25" eyepiece - I thought it was a 2" ?). The others should be OK. It does not ruin the view but you loose a little of the field of view and it becomes blurred ratherh than sharp around the field edges.

[Fozzie]

Hi John the ES is a 2" ep so not a contender at the moment. .. useful advice I'll keep an eye on ant softness at the edge, see if it bothers me to much and when it becomes apparent... could be useful to feed it back on here!