How DO you measure SNR in your images????

[Merlin66]

I know the theory and how to "calculate" the approx SNR, but how DO you actually measure the SNR in your astro-photographic images????

[Gina]

I don't   I just take what comes and try to make the best of it

[JohnC64]

Gut feel is to take multiple subs and do some sort of deviation on the values for a single pixel.  For  guided(and aligned) images, the signal should always be the same.  So any deviations must be linked to the noise

Interesting  question!

Found a paper here that describes the calculations required

John

http://www.phys.vt.edu/~jhs/phys3154/snr20040108.pdf

[JamesF]

In FireCapture there is a noise estimation feature named after Emil Kraaikamp(sp?) of AutoStakkert!2 fame.  I assume there must be a discussion of it on the interwebs somewhere, but I've not found it yet.

James

[glappkaeft]

In the online help (http://www.cyanogen.com/help/maximdl/HID_VIEW_INFORMATION.htm) for Maxim Dl it says:

The following measurements are made inside the aperture after first subtracting the average value in the annulus (between the middle and outer circles): [....], Intensity (sum of all pixels within aperture less background), and signal-to-noise ratio (SNR). SNR is calculated as the ratio of intensity to the standard deviation of the background times the square root of the number of pixels

[ollypenrice]

Good question, Ken. The links look promising. At the moment I just look at the image and decide I need more data. However much I've already got. 

Olly

[glappkaeft]

Good question, Ken. The links look promising. At the moment I just look at the image and decide I need more data. However much I've already got. 

Olly

There is no such thing as too much mount and too much data...