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Sharpstar 140PH Optical distortion issue Sharpstar AL-140PH · Jeko Jekov · ... · 5 · 121 · 2

jekovj 0.00
Jeko Jekov
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Hello Sharpstar Users,

The screenshot represents IC63. Two sessions, one in 2022 the other in 2023. The image train is the same: Sharpstar 140PH, reduced to 670mm with a dedicated reducer, spacers, Asi6200mc. The first picture includes Optolong L-extreme filter, the second one is with Optolong L-ultimate. The second image shows quite a distortion around bigger stars. I believe it is not caused by the filter as for the last 6-7 months i got this problem regardless the camera or filters. So far I tried Asi2600mc, Asi6200mc, Asi294mm, L-rpo filter, 6nm mono filters, L-extreme, L-ultimate and the end result is quite the same. So, obviously it is an optical issue that appeared at certain point of time and I would be very thankful if someone can share any expirience and a way to fix this.
Thanks and cheers to All!

Jeko








Screenshot 2024-03-08 123400.jpg
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andreatax 9.89
andrea tasselli
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If you mean the image on the right then does it show on any very bright stars or just Gamma Cassiopeiae?
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jekovj 0.00
Jeko Jekov
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On any star above a certain radius…
M33 for example with the same configuration but with L-pro
If you zoom in the bigger stars are all Saturn like



IMG_0666.jpeg
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andreatax 9.89
andrea tasselli
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Ok, got it. The one possible explanation is that you have striae in the glass of one of your objective's lenses. Normally the cast glass blank is heat-treated to allow stress in the glass to relax and to avoid striae but sometimes this does not happen (for a possible number of reasons) and these stresses remain and slowly relax in time causing the insurgence of such defects (striae).

Now, to avoid all doubt you should test the sciope with no extra glass between the lens and the camera, except for a IR Cut filter. Bright star (mag. 2-3) at the center of the field (sensor) for your typical exposure time. See if the effect is still there. If it is then the issue is in your scope objective, otherwise it is elsewhere.
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jekovj 0.00
Jeko Jekov
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Thank you for the info. Bad news after allsmile
I have been using this scope for more than 2 years and it provided a lot of wonderful images. All of a sudden a misalignment appeared and there is no way to fix this except of replacement?…
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