How long can you keep Calibration frames

[JohnDeathridge]

Hi all question for you on how long you can safely keep and use calibration frames please.

Dark frames I thought reading various posts that you can store a set of master darks for about 3 months correct? Obviously they must match light frames exp etc.

Flat frames ?

Bias frames I have seen that generally modern cmos do not require or are not recommended.

Dark flats some people I have read seem to use both these and darks ?

[Carole]

I am afraid I kept my previous darks for 2 years!!!

Flats I re-use if I have not moved the equipment.

Bias I don't use, dark flats I don't use.

Mine are Atik EX CCD chips. 

Carole

[The Thing]

Hi John,

CCDs I believe were more prone to change of hot pixels etc. If you dither exposures then a lot of the issues with hot pixels and noise patterns are reduced if not eliminated. I use the same darks for a good few months. I have cooled CMOS cameras and even at just -5c there is very little noise, I redo the darks when the fancy takes me, I have a sequence which produces a whole set from 10s to 4 minutes, so I can set it off overnight and have a folder full in the morning.

I use the NINA Flats wizard every session after a bout of moving donuts caused by shifting dust. It produces flats and darkflats (I put a dark slide in the filter drawer). If you put the target name in at the top the files end up in the same folder as your subs, very convenient.

I don't use BIAS frames although my QHY294 OSC camera lets you record the overscan (unused edges) of the CMOS so you effectively get a Bias record for every frame, this helps with CMOS as the bias value can vary every frame.

Hope that helps.

[JohnDeathridge]

Really appreciated all learning a lot can be at times frustrating but that's what makes it fun