18 Nov 2020 AR2783 and prominence

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Fabio_Imm
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18 Nov 2020 AR2783 and prominence

Post by Fabio_Imm » Wed Nov 18, 2020 3:18 pm

After ten days of rain, finally a sunny day!

Seeing was mediocre, with the usual whitish haziness.
SS60 Quark etalon on an 80ED scope
Basler acA1920-155um

Image2020-11-18_T1 by Fabio Immovilli, su Flickr

Also captured my first prominence :hamster: , found it an the northern limb, just opposite to AR2783

Image2020-11-18_P2crop by Fabio Immovilli, su Flickr

Concerning proms, which is the best approach to picture them: long exposures with low gain or max gain with short exposure?

Cheers
Fabio



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eroel
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Re: 18 Nov 2020 AR2783 and prominence

Post by eroel » Wed Nov 18, 2020 3:30 pm

Fabio:
You got the Sun in spite of bad seeing, so the session was a success.
Regards,
Eric.



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Re: 18 Nov 2020 AR2783 and prominence

Post by EGRAY_OBSERVATORY » Wed Nov 18, 2020 3:32 pm

Thanks Fabio.
I tried to capture the spot in WL with Baadar film, without success due to thin-clouds

Terry



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Re: 18 Nov 2020 AR2783 and prominence

Post by JochenM » Wed Nov 18, 2020 4:09 pm

Not bad at all considering the conditions, Fabio.

Regarding your question; I always try to keep the gain low (and of course that means slightly higher exposure times). More gain = more noise, which I find always shows in prominences.


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Re: 18 Nov 2020 AR2783 and prominence

Post by Fabio_Imm » Wed Nov 18, 2020 6:01 pm

Hi Jochen,
Thank you for the info.
I asked, because in today's imaging session I tried two different settings resulting in similar histogram:
a) 150 ms exposure, low gain
b) 50 ms exposure, max gain
After stacking and post processing I found no difference between a) and b) in terms of noise (maybe it got averaged out by the stacking?)
but b) was noticeably more crisp in details.

Anyway, this was just a single quick test, I'll investigate further under better seeing conditions.

Cheers
Fabio



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Re: 18 Nov 2020 AR2783 and prominence

Post by rsfoto » Wed Nov 18, 2020 7:25 pm

Hi,

Very good.


regards Rainer

Observatorio Real de 14 San Luis Potosi Mexico

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Re: 18 Nov 2020 AR2783 and prominence

Post by yltansg » Wed Nov 18, 2020 9:34 pm

Hi Fabio,

You should also try different gamma setting.

Alfred



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Re: 18 Nov 2020 AR2783 and prominence

Post by MapleRidge » Thu Nov 19, 2020 3:55 am

Nice images of the AR and prom Fabio...well done !!!

Brian


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Re: 18 Nov 2020 AR2783 and prominence

Post by Montana » Thu Nov 19, 2020 12:09 pm

Wonderful images :bow :hamster: the prom is fabulous :hamster:

I would answer the same as all the above. It is a question of testing in your system, you want as low gain as you can get away with and as quick an exposure as you can get away with. You have to balance the two out. Every prominence is different so difficult to always use the same method each time. For each prom I usually image a range of gain vs exp and see which comes out best. Also, like Alfred said, play with the gamma too. Increasing the gamma can also make it easier to see the prom and lower the exposure, but be cautious! the more gamma you add the more white haze you get and the more stacking artefacts you get. I only change this marginally as I have learned the hard way :)

Alexandra



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Re: 18 Nov 2020 AR2783 and prominence

Post by Fabio_Imm » Thu Nov 19, 2020 6:40 pm

Hi Alexandra,
Thank you for your suggestions.
I noticed that below a certain amount of gain I was losing details (or dynamic resolution), even if by increasing the exposure the hystogram was similar.
Time for more experiments :)
Actually I never touched the gamma slider during acquisition: I was under the impression that it could always be corrected in post-processing.

Cheers
Fabio



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