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Old 29-08-2020, 08:52 AM
Startrek (Martin)
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Creating Flats in APT

Appreciate some advice in making flats in APT
My camera is a new ZWOASI2600MC ( full well 50,000e )
Telescopes 6 and 8 newts
APT CCD Flats Aid
Target ADU ?
ADU range ?
Starting Exposure ?
Minimal Exposure ?
Max exposure ?
Binning obviously 1x1

NB: I realise your focus has to be spot on

Thanks in advance
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Old 29-08-2020, 09:49 PM
Startrek (Martin)
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Did some testing tonight using the APT flats aid , a white T shirt and a small portable led flood light
Not a great result but Im getting to understand whats required to achieve good flats

Has anyone used an illuminated drawing or Tracing panel. The illumination on these tracing panels looks fairly even compared to a commercial led lighting panel

Office works have one in A3 size (400 x300 ) with 3 adjustable brightness settings for under $100 and it would cover the objective of both my 6 and 8
newts

Comments welcome !!
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Old 29-08-2020, 10:17 PM
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xa-coupe (Jeff)
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I've got one of those panels, and I''m wary of it as it seems to be made of a lot of little cells to reflect the light .. I'm not sure if this will show through. I have thought of putting a sheet of paper of it to diffuse it too. Also worth mentioning that they have a cyan colour cast that you may need to fix. Someone got a studio lighting gel to fix it.
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Old 29-08-2020, 11:20 PM
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luka
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The little cells will be completely out of focus and do not matter.
Also the colour cast should not matter, as long as emitted light has all 3 main components (RGB) to go through the Bayer matrix of the OSC sensor.

By the way, I tried "cheating" with the A4 panel on 8" and it was just not big enough. Just.

You can find the panels cheaper on ebay, A3 for under $50.
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Old 01-09-2020, 07:47 PM
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The_bluester (Paul)
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I have an A3 panel controlled by an Arduino board.

Martin, I have not sorted flats yet on my 2600 as I have not had enough time to fiddle yet. I reckon somewhere around 20 to 30K will be the ticket on 0 gain, not sure on 100 gain. The ASI294 was very twitchy to do flats on and needed long flat exposures but I am hoping to get away with one second or less with the 2600 and to be able to use bias frames rather thsn dark flats as my imaging software (Voyager) is apparently very good at doing auto dawn and dusk flats, even to the point of dithering the mount in case of some stars still showing up (So they integrate out of the master flat)

Last edited by The_bluester; 01-09-2020 at 08:01 PM.
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Old 01-09-2020, 09:08 PM
Startrek (Martin)
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Paul
I capture some flats last night using an A3 led sketching panel which has touch control adjustable illumination
I fashioned a piece of cardboard cut a hole the size of the OTA and sprayed it Matt black then attached it to the panel with a 20mm stand off surround
Manually slew the scope vertical in non tracking mode and sat it on top
Took 15 at 20,000 ADU, 25,000 ADU and 30,000 ADU ( HDR gain 0 )
Flats turned out ok but one corner of the frame is not uniform. The 20,000 ADU seemed to be the best of the three settings
I used these flats in my NGC 104 Tuc 47 image posted today in Beginners AP
Definitely corrected the vignetting and 2 faint dust motes
Cheers
Martin
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Old 02-09-2020, 12:28 PM
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The_bluester (Paul)
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When did you shoot them? I know that flats are a very good way to find light leaks that you did not know about if you shoot them in daight.

There were some bolt holes that look to be blanked off at the inside end in my SCT but if I shot flats in light conditions you get some really interesting patterns! Some foil backed tape solved that.
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