Is it ok to reuse flat frames?

[Jerry Barnes]

I’ve read one of the advantages of a cooled camera is having a library of calibration frames instead of taking darks once the clouds come over of it starts getting light.

But I wondered if that’s true for flat frames as well? 

Or perhaps only true if there isn’t any dust on filter or sensor and also that the camera doesn’t move in relation its orientation with the light frames.

After reading a recent post about missing flats I’ve started to think I should take them each time and before I disturb anything.  Maybe even buy a light box.

[Stuart1971]

Flat frames are a snapshot of the imaging train to show all the imperfections, like dust and any vignetting, so as long as nothing has moved from one session to another, so it’s all in the exact position it was when the flat frames were taken, then yes, but if anything has moved, even the focus then no…👍🏼

Edited October 11, 2021 by Stuart1971

[ONIKKINEN]

I dont think focus is all that important as long as its roughly same. Check this video out, Cuiv makes a few fair points.

 

I will say that i took flats for a while only after getting back home and sometimes on the next day. I had marked the camera-focuser point with tape to recreate the same rotation and left the focuser as it was when shooting.

 

Currently i take flats every time since it is pretty easy with a light panel. The dedicated astro light panels are hilariously expensive so i bought a 20 euro tracing tablet from amazon. Works just as well with 10% of the price.

[The Lazy Astronomer]

Ditto what's already been said. Leave the imaging train in tact, and you can reuse flats for a little while. Eventually you'll get some new dust motes or they'll move a bit and you'll need to reshoot the flats, but fortunately that's a job for the daytime/cloudy night.

[Jerry Barnes]

Thanks both, plenty of cloudy nights to update my flats!