Making Flats in Sharpcap

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DanK
Posts: 83
Joined: Sat Dec 28, 2019 9:58 pm

Making Flats in Sharpcap

Post by DanK »

Robin:

I am finding it impossible to make flats with my flats panel from Germany. The messages I get are : "too many pixels under...", "try to get more pixels above 20% saturation" followed by "too many pixels are saturated".

Adjusting the exposure slider doesn't seem to help...there seems to be no happy medium between one contradictory message followed just the opposite.
I am limited with how much I can vary the brightness of the panel by but whatever it is isn't good enough for Sharpcap.

There has to be a better way than what I see with SC and the way it makes flats. Too fussy--next to impossible!

Dan Kahraman
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Re: Making Flats in Sharpcap

Post by admin »

Hi Dan,

if you are getting both warnings at the same time then it means that parts of the image are above 80% brightness and other parts below 20% - that indicates pretty strong vignetting near the frame corners (a factor of 4 dimmer or more), which is always going to make flats hard to work with since the size of the correction in those areas is going to be large.

In that situation you need to judge the histogram for yourself - really aim for nothing above 90% brightness as you may run into sensor non-linearity near saturation. On the other hand, you want the darkest areas to be as bright as possible, so turn up the brightness until you are just getting some bits of the image touching 90% brightness levels. You may still find that correction in the very dark corner areas is not quite perfect, but you will have done the best you can.

cheers,

Robin
DanK
Posts: 83
Joined: Sat Dec 28, 2019 9:58 pm

Re: Making Flats in Sharpcap

Post by DanK »

Yes I am getting both warnings simultaneously and the panel I have doesn't have enough of a variable output. With the other panel I have I can adjust the led intensity and get the histogram give me the OK signal. Adjusting the Gain and Exposures don't provide me with the proper optimal control for getting the OK.

I have to fix the other panel and its flimsy nature makes it ill suited for use as a Flats panel.

Dan Kahraman
DanK
Posts: 83
Joined: Sat Dec 28, 2019 9:58 pm

Re: Making Flats in Sharpcap

Post by DanK »

What should the histogram look like? Where should the "mono" peak be?

Dan Kahraman
DanK
Posts: 83
Joined: Sat Dec 28, 2019 9:58 pm

Re: Making Flats in Sharpcap

Post by DanK »

Just fixed my variable light output LED (soldered connections). This LED gives me the control I need to get the OK histogram from Sharpcap when I am trying to capture flats.

Keep my fingers crossed.

Dan Kahraman
DanK
Posts: 83
Joined: Sat Dec 28, 2019 9:58 pm

Re: Making Flats in Sharpcap

Post by DanK »

Robin:

I just noticed the white line and the other ones have a number associated with them. The white line value at G=100, E=1.998 sec had an ADU of ~8400 which is close enough to ((2)^14)*0.50...so I will go with that. Currently making my darks which will take much longer.

Dan Kahraman
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