L to RGB ratio

[rubecula]

So far I've been taking all images at 600sec binned 1x1.  For NB targets I've recently gone out to 1200sec exposures.  We get so few clear nights here in England that I'm wondering if I'm not making best use of the time available when it comes to LRGB imaging.  Say I took 20 x 600sec luminance binned 1x1, what would be the appropriate settings for RGB frames?

Thanks

[carastro]

I don't know what the recommendations are but I do my RGB half the length of the Luminance but bin x 2 and I do half the number of RGB to Luminance.  You would need software capable of re-sizing the RGB to do binned though.

Carole 

[vlaiv]

I don't think there is simple answer to that question.

Topic is rather complex and depends on the way you process your images among other things.

To see what is acceptable level of noise in particular color - we need to examine how people perceive difference in color based on how "distant" colors are in physical world.

For example - look at this chromaticity diagram with error contours:

Colors inside ellipses are roughly the same visually (same level of difference across the surface of the contour) but sizes / diameters of these error contours are not the same and depend on color itself.

It looks like we are the least sensitive in errors in green but we react strongly to errors in blue.

This suggests that noise in blue should be the least and eye can tolerate errors in green the most.

I've written above just to point out how complicated the topic is - I did not even start to consider relationship between luminance noise and chrominance noise and how do we perceive each.

Bottom line - maybe try out couple of approaches - same time spend on each of LRGB, twice more time for L than for R, G and B combined, binning of color and so on and just use the one you like the most, as there is no definitive answer of what is the best way to do it (maybe there is, but I don't think we know it yet).

[rubecula]

Thanks Carole & vlaiv.  Forcast is for clear skies tonight so I'll try 20 x 600 for L and 10 x 300 for RG&B