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How do you get your flats?


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I've ordered  a couple of those LED tracing panels from Amazon (15 quid a pop) because I was tired of using an iPad as a flat panel.

However... these tracing panels are edge-lit and have a significant blue cast. I'm not sure how much effect it has on the quality of the generated flats.

Anyone have experience or better alternatives?

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Last night I just took sky flats. One of the few pluses about conditions this time of year is that you can use the late evening light. Rest of the year, I use an LED tracing panel with a sheet of Perspex taped to it.

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I use an LED tracing panel with three brightness levels. I always put three sheets of white paper over it to help diffuse the light.

Never ever had any issues with my flats using this, whichever filters I'm using. The key is to make sure you hit the correct ADU value for your particular camera.

For example, my 294MM I always aim for an ADU of around 26000. Works like a charm.

Pete.

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The ADU value should be around 1/2 of ADU Max. For 16-bit sensors, the ADU Max is 65535, so 1/2 of ADU Max should be e.g. 32,000-33,000, while 30,000-35,000 is also good. The best way to check what is your ADU Max is to clip all pixels which means e.g. a 60s exposure with the scope lit by the panel or a day sky. Some programs inform about the ADU value of the picture. 

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  • 2 weeks later...

I did a t shirt flat (literally a white t shirt on the front of the scope that was pointed at the evening sky). results seemed identical to the tracing panel with 3 sheets of paper, although ASTAP didn’t complain about the color temperature of the t shirt flats…

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