Signal to Noise Calculator

[MarkS]

My (Microsoft Excel) spreadsheet for calculating Signal to Noise Ratio is here:
http://homepage.ntlworld.com/the_shelleys/photos/MDS_SignalNoiseCalculator.xls

I hope it's reasonably straightforward to use.

The main conclusions (for which I do not claim originality) are:

1) For the same exposure length, the S/N of a very dim target can be improved by a large factor by moving to dark skies
    However, for a bright target, S/N is high to begin with and little can be gained by moving to dark skies

2) For a single long exposure, the camera read noise makes very little difference to the S/N achieved.

3) Under dark skies, the read noise has a huge effect on the length of sub-exposure required to achieve the required S/N after stacking
    However, under heavy light pollution, increasing subexposure time has a very marginal effect.

4) The camera dark current is a critical limiting factor for achieving good S/N for a dim target in the Summer

5)  Note that a more sensitive CCD would increase target brightness and sky flux simultaneously (in measured electrons/minute)
     Improving the F ratio (e.g. by using a focal reducer) would have a similar effect.
     Doing either has a big effect on the S/N achieved

[Fay]

Mark, I think when you were born, you was given Einstein's brain!!!!!!!! Wow!

Fay

[Mike]

Mark, I think when you were born, you was given Einstein's brain!!!!!!!!

Ugh !! Surely it would be all decomposed and gross by now?

[Rocket Pooch]

John and I we're talking about this last week on the phone, that's why its less important to have lots of darks under highly light polluted skies and more important to do them when the sky is clear, also flats are handy.

There a conversation for the Bull on Thursday!!!

[Fay]

That sounds promising

[Ian]

our conversations are usually full of bull...

[mickw]

I think I'd better start drinking now 

[Fay]

Thank God for you, Mick, I thought I was going to have to pretend to be clever!!!!!