Quote:
Originally Posted by Shiraz
these are some of the best references out there Bert - thanks.
the ideal exposure calculators provide "optimum" sub exposure time (read noise = 5% total), but not the overall exposure needed for a given object. Do you have any ideas on what overall SNR is required to get a "good" image?
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It purely depends on how 'bright' the target is. A low signal to noise will record bright stars in seconds. As objects get dimmer the signal to noise needs to be far higher. This is so that the dim signal is larger than the noise. If it is not, it will never be recorded!
If the signal is just above the noise then the integrated sampling time needs to be very long to improve the ratio of S/N.
As in all of science it is the signal to noise ratio that is the only dogma for evaluating data.
We must never forget though that one human's noise can be another human's signal. Even then the measuring system must differentiate between the two. I changed man to human for Jocelyn Bell who really was the 'man' to discover pulsars and was ignored in the Nobel Prize!
Bert