For ASI183 From Shiraz, original Excel from Steven Bellavia: here revised version: here in google drive comparison of different approach for ASI 1600: Steven has made the excel for ASI071, ASI1600, ASI183, ASI2600, ASI294, ASI533, ASI6200 with some minor adjustments, these should be useable on QHY, Toucam and other alternatives cloudynights cloudynights 2 LHiRES ESO VISTA Exposure calculator Gemini howard group mirametric online SNR calculator