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Please help me star test this scope

Started by gy60356, 06/13/2007 01:54AM
Posted 06/13/2007 01:54AM Opening Post
Forum Member

Join Date: Apr 2002

Location: Morgantown WV, US

Posts: 129

Hello Group,

I did a star test for my refractor yesterday with a ToUcam. The ones on the top are with a green filter and the ones below are without any filter. Each image is a average of approx. 150 frames. No additional processing was applied to the image. Now, I really need your experts' comments on the optical quality of this scope 8)

Clear Skies,
Gu

Attached Image:

gy60356's attachment for post 37489
Posted 06/13/2007 06:10AM | Edited 06/13/2007 06:14AM #1
I would say it is a "good" lens. The green patterns
are very slighly out-of-round indicating some weak
astigmatism (maybe 1/8 wave PTV) or slight pinch.
The center and edge of the right pattern are a little
bright indicating a little zones or spherical.

The color images show a funny vertical wave running through
near the center of the lens -- perhaps some striae or
irregularity in the glass.

Lots of chromatic aberration. Looks a good achromat of
moderate F-ratio.

You can have great fun trying to model this stuff with
Aberrator. Here is a quick try. Not perfect, but
does show some of the basic features. 96% Strehl ratio
perhaps? Could probably pin it down better with
images nearer to focus.

If you've still got the raw images, you could try running
them through a Roddier test. What lens is this?

Attached Image:

m87's attachment for post 114722
Posted 06/18/2007 02:06PM | Edited 06/18/2007 02:09PM #2
Yeah, yeah, yeah, a lot of talk but does he have a nice scope? I agree with John and would say yes. I see nothing that jumps out as a problem. Sure, there does seem to be some subtle stuff going on but, overall, it appears, at least to me, to be a decent lens.

Gu:

Do you get sharp images, both stellar & planetary? If so, be happy!

Jeff

"Don't sweat the petty things and don't pet the sweaty things" 8O