My take on AR2781

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Fabio_Imm
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My take on AR2781

Post by Fabio_Imm » Fri Nov 06, 2020 2:32 pm

Hello, finally this morning the clouds moved away and I had some time to image the sun.

Daystar Solar Scout SS60ds
Basler aca2040-35gm (full disk image)
Basler aca1300-30gm (detail view)
Genika + Autostakkert + Registax 6

As you can see, I am still struggling with Newton rings.
5ccw__2020-11-06.png
5ccw__2020-11-06.png (462.79 KiB) Viewed 175 times
2020-11-06_T.png
2020-11-06_T.png (960.12 KiB) Viewed 175 times
Higher resolution images in my Flickr repository

Clear skies

Fabio



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rsfoto
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Re: My take on AR2781

Post by rsfoto » Fri Nov 06, 2020 4:07 pm

Hi,

Very good images and details. Yes, Newton rings can be a nuisance ...


regards Rainer

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Alto
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Re: My take on AR2781

Post by Alto » Fri Nov 06, 2020 4:15 pm

Newton has a lot to answer for!

Good shots though....


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Doesn't mean I know what I'm doing, though!

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Carbon60
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Re: My take on AR2781

Post by Carbon60 » Sat Nov 07, 2020 7:55 am

Nice images Fabio. The only solution I know of to defeat NRs is to tilt the camera, although some cameras are more of a challenge than others. My Basler acA1920-155um is quite forgiving, but my acA2440-75 poses more of a problem. Have you tried this approach?

Stu.


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Fabio_Imm
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Re: My take on AR2781

Post by Fabio_Imm » Sat Nov 07, 2020 8:36 am

Hi Stuart,
Thank you for pointing that out: a tilt adapter is on it's way.
Given your experience do you think that I need one tilt adapter for every camera? (e.g. each camera requiring a particular tilt angle)

I noticed too that certain cameras are more forgiving than others and they all come with their pros and cons: the aca2040-35gm is lovely with this setup as it provides a full disk view at the prime focus. However in post-processing I noticed quite substantial fixed pattern noise (a sort of checkering) when using very low exposure times... I should try to take a calibration frame as well.

One thing that puzzles me when dealing with Newton rings in closeup shots using a flat frame (FF) with my setup: if the FF is taken using a diffuser in front of the lens without touching focus, the results are much better. If the FF is taken by defocusing then the results are crappy as in the previous picture. At least with my setup, it seems that defocusing (without changing the camera-etalon relative position) alters the rings max-min pattern rendering the flat field useless.

Cheers

Fabio



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Re: My take on AR2781

Post by EGRAY_OBSERVATORY » Sat Nov 07, 2020 12:10 pm

Thanks Fabio for your excellent examples of NR's, which I know is quite frustrating - from my past images and one particular image yesterday (posted) where to add my TeleVue 2.5X Powermate, simply wrecked the close-up image of a spiked-prom.

Using a cheaper Revelation 2X Barlow, didn't show any NR's of other images - tested. I ran out of time to do a direct comparison of the published image with the 2X item, due to low Sun-light below an obstruction.

Best Wishes
Terry



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