Binning of rgb data

[newbie alert]

Hi guys, could anyone explain the reasons of binning the rgb data as I've only tried it once..it just seemed to reduce the frame size( I suppose by a factor of 4) can't see the benefits, I'm sure there are but can't quite see it myself yet

[vlaiv]

Yes, binning will reduce pixel count in height and width. People do it with RGB data because of following:

- Larger pixel surface (4 adjacent pixels joined) will gather more light. It enables you to achieve almost x2 SNR in same imaging time versus regular pixel size

- Human eye/brain is less sensitive in variations of color than it is in variations of brightness (luminance)

This enables you to get color data in less time and still have acceptable quality of image. Larger pixels means that you will probably be under sampling so you wont capture all the sharpness that you possibly could, but that is in color data - and eye/brain won't be bothered too much as most of sharpness that it can see will come from luminance data due to way our vision works.

[Dragon_Astro]

So if luminance is captured 1x1 and colour binned at 2x2, would astro software match all the stacked subs, size wise?

[vlaiv]

Just now, Dragon_Astro said:

So if luminance is captured 1x1 and colour binned at 2x2, would astro software match all the stacked subs, size wise?

Should be able to do if such feature is implemented - it's really nothing special, subs are interpolated when alignment is performed, you can upsample RGB data in the process of resampling.

If you are using software that does not have this feature - you can do it yourself. Take calibrated RGB subs and enlarge them x2 in some other software. Use nice resampling method like Lanczos or Spline resampling for that. Be careful not to use software that can't handle 32bit data - you want your subs to keep all the information.

[ollypenrice]

If you bin your colour you simply resize it to the pixel dimensions of your luminance data in Photoshop or any number of other graphics programs.

Should you bin your colour? It depends on your imaging scale to start with. If you are close to the seeing limits of your sky while shooting unbinned then binning colour might make sense. But, even then, it depends on how you process. I never bin colour because I often want to use it separately in processing. RGB stars without luminance are often better than LRGB stars - provided they are not binned. And I may want to use my RGB data to rescue over-exposed cores in bright galaxies, for instance.

There's another reason I don't bin colour as well: I find it's a mess. I don't know why and I won't insist on this point because, having tried it and found I didn't like it, I stopped doing it rather than trying to get to the bottom of it!

Olly

[carastro]

I always bin my colour data as I get limited time in a dark location and in any case there is too much cloud around in the UK, so it enables me to complete any image more quickly.

I re-size the frames in Registar, but I think there are a few other programmes that will do it too.  

Carole 

[DaveS]

AstroArt5 will resize your frames too, though as yet I've only done the occasional experiment.

This will almost certainly change when I get the ODK12 and 16200 setup, 1x1 gives a slightly iffy 0.62"pp, 2x2 a more sensible 1.22"pp.

[newbie alert]

11 hours ago, vlaiv said:

Larger pixels means that you will probably be under sampling so you wont capture all the sharpness

Thanks Vlaiv, I'm already undersampling with my current setup atm

[newbie alert]

Thanks for all replies , appreciated..

[ollypenrice]

11 hours ago, DaveS said:

AstroArt5 will resize your frames too, though as yet I've only done the occasional experiment.

This will almost certainly change when I get the ODK12 and 16200 setup, 1x1 gives a slightly iffy 0.62"pp, 2x2 a more sensible 1.22"pp.

This will be interesting to hear about. Yves and I intended to bin the colour and maybe the luminance from his ODK14 but the camera wouldn't do it. It produced artefacts at the edge of the stars so the experiment ended there.

Olly