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Old 20-05-2021, 10:56 AM
Emuhead (Andrew)
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Different gain (or exposure lengths) per filter?

Hi all,

Different gain (or exposure lengths) per filter?

Is this standard practice or not recommended?
My Ha is always clean & bright, and Oiii & moreso Sii usually not even close. Trying to avoid noisey data, and sure i could just take more Oiii & Sii subs, but is there any reason i couldn't just increase the gain and/or exposure lengths for Oiii & Sii, then linear fit all 3 stacks later?

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Old 20-05-2021, 02:28 PM
Imme (Jon)
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I use 3nm O3/S2 and 5nm Ha filters and basically always use shorter sub length for Ha to get similar signals across the board
I prefer not to change gain as when i find something that works i stick with it.

Just remember if you change sub length on a single filter then darks will need to be adjusted accordingly
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Old 20-05-2021, 04:41 PM
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An interesting question. I always use the same exposure lengths but yes the Ha is usually the strongest by far. That means turning it down in Photoshop with a hue/saturation layer. Turning down the lightness slider.

I think its just adding too much complication. Especially with CMOS cameras.
You've already got to match gain and offset as well as temperature and exposure length plus same binning. Yet another change is going to lead to mistakes and waste.

If you use QHY 268 or 600 cameras you also add the readout mode as another variable. Its too much in my opinion.

I do Ha in 1x1 and O111 and S11 in 2x2 binning. That evens it out a bit.

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