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Luminance or no luminance

Started by ddoctor, 02/15/2007 06:24AM
Posted 02/15/2007 06:24AM Opening Post
hi group,
question on when it helps to have luminance data. specifically, with my set-up, no binning yields an image scale of about 1.04 arc sec, 2x2 about twice that. i would imagine the seeing here in the northeast us is rarely good enough to go without binning in my case. so that is why typically when imaging i am binning 2x2. so the questions are:
1) if the seeing does not support 1x1, is it even worth your time to try to accumulate the 'high res' data.
2) should you take luminance at 2x2 and rgb at 3x3?
thanks for your time,
dave
Posted 02/15/2007 08:56AM | Edited 02/15/2007 09:30AM #1
>>2) should you take luminance at 2x2 and rgb at 3x3? >>

It's all about signal to noise. That is fixed, regardless of binning, and is primarily a function of aperture.

Some say there is no gain to binning except for reduction of download time and small reduction of download noise. You can try this experiment. Try a 10 second shot binned 1x1, then 2x2. Then take the 1x1 binned image and resize it to half size to equal the 2x2 binned image. Is the signal to noise the same? I suspect it would be for non-ABG cameras, but in ABG cameras there might be an advantage to the binned image.

A similar issue arises whether or not to telecompress to attain more signal with a faster F-ratio. If it's true that signal to noise is constant and varies only with aperture, then there would be no gain by telecompressing. In fact, you lose some resolution if you compress too much. My own criteria for compressing is to use it only to achieve a wider field, if the object does not fit at prime focus.

Rolando