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LRGB, how many subs each?

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#1 Calzunen

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Posted 29 January 2022 - 06:57 AM

when shooting LRGB data, should L be 3 times as more as RGB data, is that what "most people aim for? and does bin 2x2 work on asi 1600 for RGB? (I´ve read that binning isnt really worth it on this camera)



#2 pyrasanth

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Posted 29 January 2022 - 07:25 AM

I aim for a ratio of 2-3 subs per each of RGB. My current M66 image is currently at about 3 to 1 and I will try and maintain that ratio moving forward when I take more data.

 

Binning wil increase your SNR and allow you to reach the optimal sampling for the optics you are using. It is a waste of time to over sample and equally under sampling will lose you detail- so there is a sweet spot for all optical configurations based around your optics and seeing conditions.

 

On my C14 I bin my ASI6200 at 3x3 as I know I'm never going to get better resolution than 0.84 arc secs on most nights so it seems mute not to have the extra SNR and the subsequent smaller images that help with the processing. I guess if I do get better seeing drizzling the data will help to recover lost info as I always dither on every sub.

 

Since there is not as much spatial information contained in the RGB data you can bin that to pretty however much you want and then use the higher spatial information of the luminance frame to light up the RGB with the detail intact.

 

I find it easier to be working with mono cameras as they have greater flexibility with regard to binning.


Edited by pyrasanth, 29 January 2022 - 07:31 AM.

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#3 kathyastro

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Posted 29 January 2022 - 08:02 AM

I bin my RGB 2x2 and take shorter exposures than the L.  For a typical session, I will take 10 each RGB frames at 120 sec, and 10 L frames as 300 sec.  Why 10?  Because 8 is the minimum for Windsorized Sigma Clipping and 10 gives me some room if I need to throw out one or two.

 

My total exposure time for a typical LRGB session ends up being 60 minutes of RGB (20 per channel) and 50 minutes of Lum.  Of course, I will go longer if the target warrants it.  Usually, I will increase the number of L subs before I increase the RGB.


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