Master Calibration Frames Questions

[sreilly]

I have just installed an Alnitak Flat-Man XL panel in my observatory and was wondering what approach people are using to create their master frames. Mainly interested in the number of bias frames used to make the master and why as well as for the darks and flats. In the past I've generally used 5 flats, 10 darks and 20 bias frames when creating my masters but now that I have a high quality EL panel taking flats using ACP has become quit painless as I can do them any evening regardless of weather so the number of frames isn't a time constraint. I also use a rotator so I take east side and west side flats although I intend to do some experimenting to see if they are different at all. The only way I know to do this is use a master east frame to flat a master west flat. If the doughnuts disappear  that I think it may be safe to think this is  a proper line of thought. Any suggestions or am I missing something here?

The darks and bias frames are also able to be done on nights not good for imaging and my thought here is to create a more update library. Taking lots of calibration frames shouldn't be an issue as you can make the masters and then delete the individual frames saving only master frames. I'd likely save these master frames with data they were used on such as the object they were used to calibrate in one folder with the folders of those nights data in sub folders. There might be some redundant master frames over time but at least not near as many frames as all the individual used to make them. Does this make sense or do you have a better solution?

Thanks,

Steve

[sreilly]

OK, quick test of using a west side flat on an east side master doesn't work at all. I guess I was wrong about that so now I need to pay more attention to when the mount flips during the processing run. As this is done automatically when using ACP with my AP1200 I'll need to look at the starting exposure times and side of pier in the fits header window. Guess I was trying to make this too easy.

-Steve

[Nocturnal]

Hi Steve,

it's pretty simple. Take as many calibration frames as you can afford. I regularly use 100 flats and 100 bias frames. The more frames the better the SNR and the better the SNR the less noise they add to your lights during calibration. Where you put the limit depends on how much effort the result is worth to you. We all have different breaking points

You were not doing yourself any favors using only 5 flats in the past. Most likely you'll be pleasantly surprised how much better your images get when you take tons of them. Once you have 100 flats simply do a test where you calibrate with 5 flats and with 100. See if the difference is noticeable to you.