Flats

Discussions of Electronically Assisted Astronomy using the Live Stacking feature.
festoon
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Flats

Post by festoon » Mon Feb 04, 2019 3:52 pm

I seem to be having a problem getting flats to work. I'm using a Atik 414EX with sharpcap 3.2 for near time imaging using the live stack function.
The first attached file is a screenshot before flat taken
raw.PNG
raw.PNG (855.17 KiB) Viewed 184 times
The second shows the histogram setting up the flat
setupflat_1.PNG
setupflat_1.PNG (344.74 KiB) Viewed 184 times
The third shows after the flat is applied
Capture_flat.PNG
Capture_flat.PNG (502.9 KiB) Viewed 184 times
I would also attach the image flat file but is saying image too large when I try and upload it (2.75Mb)
Is there something I am doing wrong? Thanks :)

BlackWikkett
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Re: Flats

Post by BlackWikkett » Mon Feb 04, 2019 5:19 pm

Hi festoon,

I notice in your capture format you have .ser format selected. Click the auto button this will you to change the output format. Change this to .fits and try again.

-Wikkett

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admin
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Re: Flats

Post by admin » Mon Feb 04, 2019 6:56 pm

Hi,

The output format you have selected shouldn't be a problem as the flat capture process will automatically change the output format to the one that it needs. If you could share one of the flat frames with me (perhaps upload it to a site like dropbox and then share a link) then I will have a chance to have a look and see if I can work out what is going wrong.

Cheers, Robin

festoon
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Re: Flats

Post by festoon » Mon Feb 04, 2019 8:42 pm

Thanks guys for the help :)
Here a link to the flat file
https://drive.google.com/open?id=1hLS6d ... gHiCZcq3AA
Let me know if it doesn't work.
You can see the same thing in the file, which makes me think its part of the flat acquisition process

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turfpit
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Re: Flats

Post by turfpit » Mon Feb 04, 2019 9:19 pm

Festoon

This is a flat taken with my Atik 314E (mono). Home made EL panel which hangs over the end of the scope. 25ms exposure was the setting to get the histogram just left of centre ~40%.

Dave

Atik314E-flat-0.025s.JPG
Atik314E-flat-0.025s.JPG (62.02 KiB) Viewed 161 times

festoon
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Re: Flats

Post by festoon » Mon Feb 04, 2019 9:29 pm

Thanks Dave..I'd say yours looks very good :)

festoon
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Re: Flats

Post by festoon » Tue Feb 05, 2019 2:09 pm

Also here is a link to the raw image that is used to create the flat....so if I understand correctly this is averaged 10 times to create the flat
https://drive.google.com/open?id=1Il0gf ... WjCmEkqcVl
I dont see the diagonal band in this

festoon
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Re: Flats

Post by festoon » Wed Feb 06, 2019 9:09 am

Did a few more investigations on this last night.
To begin with, I tried using Astro Live, and performed a flat capture on this (10 averages), which worked fine, and after applying the flat, none of the effects shown in sharpcap occured, and the image was lovely and flat afterwards.
I was also able to use the saved flat file from astro live and apply it in Sharpcap successfully.
This implies it is not the camera which is the issue, or the way the flat is applied to the image in sharpcap, but it implies the issue lies with how the flat is acquired in sharpcap.
One thing I did notice, in Sharpcap, when capturing a flat frame, is when you choose number of frames to average to be 10 - it seems to count up to 11 and not 10. I thought this was rather strange. I don't know if this is connected, but thought I should mention, in case it helps.
Thanks again for your help :)

Astrogate
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Re: Flats

Post by Astrogate » Wed Feb 06, 2019 5:51 pm

I have noticed the same issue with the flat counting procedure (not sure if dark does the same) and thought that something is strange about this behavior.

Chris

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Re: Flats

Post by admin » Wed Feb 06, 2019 7:35 pm

Hi,

The capture of an extra flat frame is deliberate (and the same happens when capturing darks too). This is because the end-user might press the start button just after they have put the flat frame illumination (or covered the sense of the darks) so the first frame that comes through from the camera after that point in time may have been started before the user clicked the button and therefore not be correctly illuminated. To avoid problems like this SharpCap takes an extra frame and discards the first frame captured.

Hope this helps, Robin

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