BW-Optik 30mm 80˚ Ultrawide
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.

Overall Rating: 7
Optics:7 Value:9
Weight: 10 (Trustworthy Vote)
Date:
By:
Link to this vote: http://excelsis.com/1.0/displayvote.php?voteid=354966

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>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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