Quote:
Originally Posted by ngcles
Rod, just a thought about the 31mm T5 with your 'scope.
At f/5, the 31mm T5 will give you x82.6 magnification with a field just on 1 degree -- _but_ the exit-pupil will be just on 6.1mm. A bit on the marginal side I'd reckon unless you've got "teenage eyes".
I've got a 26mm T5 instead (mainly for that reason) but, had I tried the William Optics 28mm UWAN before I purchased the 26mm T5, I would have bought the UWAN. It is a wonderful eyepiece (equally good as the Nagler I think) with the same apparent field as a Nagler design, appears to be just as sharp and contasty but somewhat cheaper and would have provided a slightly larger true field.
They also make a 16mm UWAN, but I don't think it is as good as the 16mm T2 or T5 (I've got the T2).
Matter for you, but seriously consider the 28mm UWAN before you outlay the cash on that 31mm T5 -- slightly smaller true field I know, but, the 5.5mm exit-pupil makes it a bit more comfortable to fit it all in your iris and a lot more comfortable on the credit-card.
Best,
Les D
Contributing Editor
AS&T
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Thanks for your thoughtfulness, Les, in making those suggestions.
At that focal length, I will be using a Paracorr which whatever Ep I get. As I understand it, the effect of the Paracorr is to transform the 31 Nagler into having an actual focal length of about 26.35mm. I am assuming the exit pupil is similarly adjusted, and would end up being about 5.2mm?
I have used RB's 31 Nagler in the Mary Rose, and the view was stupendous. But I will certainly look out to try a 28mm UWAN before parting with my cash. I seem to remember trying Joe's at Kulnura one time, and while it performed well in his SCT, at the faster focal ratio of my scope, it deteriorated very badly at the fringes (not just coma).
As I still have many years of observing ahead of me, I don't mind shelling out a bit more for my EP's. Spending $800 on a 31 Nagler ends up costing me 40 cents per week over the next 40 years.
