Overall Rating: 7
Weight: 10 (Trustworthy Vote)
Date: 06/08/2004 02:26:11 pm PST
Link to this vote: http://excelsis.com/1.0/displayvote.php?voteid=354966
>Overall a fairly respectable eyepiece for the money. I was quite surprised. The throughput is very good, coatings seemed good, comfortable to use, and very nice for daytime use too.
>However at night, it's very obvious that it doesn't come close to the 31 Nagler in performance (or the UO 40mm MK-70), especially at the edges, and in faster scopes. While very sharp on axis (I was impressed there), the BW starts to exhibit softness around 50% out from center and continues to get worse towards the field stop. The last 7%-10% is almost unacceptable, and shows astigmatism too, even in an f/7 scope. The eyepiece also suffers from quite a bit of curvature, and there's just no way to make the stars appear to be anywhere close to in focus all the way across the field.
>One thing I did notice is that the eyepiece appeared to be more like a 32mm-35mm rather than 30mm. Several objects appeared to have smaller angular size than in the 31mm Nagler, and I'm not sure the AFOV is really 80* either. The difference between the 82* of the 31 Nag and the supposed 80* of the BW is significantly more than what I expected, and I'd say mine is probably closer to 75* - not much larger than the AFOV on the MK-70. I have not verified this with star timings, but objects just appear to be less magnified than in the 31.
>It's a good value no doubt, and I'd say it's worth it even for daytime use only, where I think it is better suited. But I think there's other eyepieces out there that aren't too much more expensive that will perform noticeably better for astronomical use. I'll be selling mine very soon.
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