I added a new feature to the Gain and Sub-Exposure Calculator Spreadsheets for ZWO Cameras.
You can now choose a filter and it will auto-populate the wavelength and bandpass.
This is what is available in the drop-down list, but I can add more:
Ha 12 nm
Ha 3 nm
OIII 12 nm
OIII 3 nm
SII 12 nm
SII 3 nm
So far the spreadsheet is available for the following ZWO cameras:
071, 183, 294, 533, 1600, 2600 and 6200
The link to download a copy of the spreadsheet for your use (no edit permission):
Note that if you have a One-Shot-Color (OSC) version of any of these cameras, pick the Green Filter.
I am currently working on several QHY cameras. I will let you know when those are complete. They too will have this new filter drop-down list feature.
Same notes as before, but posting here again:
1. Much of the theory and equations came from Jon Rista, Frank, Craig Stark, and others (Thank you!)
2. I recommend to only use the main (first) sheet. Blue boxes are for user entry, everything else is calculated for you. If you don't want to use image data to calculate the sky background and camera dark current, just enter those values directly to the best of your ability, but it will remove the calculation. Instructions how to restore it or on the spreadsheet.
3. The "Transmission Efficiency" of the entire optical system is likely the largest potential source of error. Play with it until your data matches a hand-held SQM, or known sky brightness value. I find 0.5 to 0.7 works for me.
4. The common thinking is you want a Swamp Factor of around 10. However, with narrow-band, especially at darker sites, this becomes impracticable.
5. I arbitrarily fixed the "object signal" to 22.0 magnitude/square arc-second. This is to compare imaging an object from two different sites, with different sky brightness, so as to have an apples-to-apples comparison. If you actually know your object's brightness, change the "22" in that equation to the desired value. This will only affect SNR calculations.
5. It is just a guide. No precision was intended. The camera specifications were obtained by eyeballing the graphs that ZWO posts on their website, or from users who submitted data using SharpCap, etc. Feel free to contact me with better data, if you have it.
7. Offset (Bias) values seem to vary, and the values I have chosen are just a guide. ZWO often divides by 5 for some reason. i.e., multiply the ZWO offset by 5 to get the camera ADU's (But not always).
8. These spreadsheets are not all that different form the Gain and Sub-exposure tables posted on other CN threads and should have similar results as running SharpCap's Smart Histogram, live in the field.
Special thanks to Nik Coli, and John Upton, who have been running these spreadsheets on their 183, 294 and 1600, and finding and fixing all my errors.
Edited by StevenBellavia, 30 January 2021 - 09:09 AM.