2x2 bin ?

[Daniel-K]

out last night taking subs and i have always wondered what this was so last night i clicked 2x2 bin when imaging m27 it made the image smaller but more detail ??? what does it really do?

[Stephen]

It combines N by N pixels into one "super" pixel which gather data/light faster, but at reduced resolution

It's useful for LRGB imaging, as the detail is all in the L channel (so you shoot that 1x1)

Then to save time, you shoot the RGB in 2x2 and stretch it to the same scale as the L channel.

[Daniel-K]

ah okies so not worth it for mono?

[Stephen]

ah okies so not worth it for mono?

For the mono/luminescence channel no.

For the RGB components, yes (though may depend on target)

[dph1nm]

Binning reduces the read noise (you only get one dose instead of four). So if read noise is a significant fraction of your total noise then it is worth binning.

NIgelM

[ollypenrice]

Once you have a focal length-pixel size which has you trying to image at a resolution greater than the seeing allows you might well decide to bin everything including luminance. This is routinely done by imagers with big SCTs, RCs etc. Yves and I would be doing this with the ODK 14 but the camera doesn't like binning and throws up artefacts.

At short FLs, don't bin. I recently compared an old shoot of the Sagittarius Triplet (FL328mm) and binned colour with a reshoot unbinned. It's a no brainer. The unbinned is way better.

With yer average CCD camera the price for binning in terms of lost quality becomes very slight at around a metre, depending on pixel size. But there is always a price to be paid till you reach the limit of the seeing. It will show in the stars.

Adding an Ha layer? Don't bin. You will get a nasty mis-match in star size and your halo issues will multiply! (Again, this presumably won't apply to very long FLs though I don't know that from experience.) I know I never bin on a project involving an Ha layer even at a metre of FL.

Olly