Stacking stacked files

[Eddy Timmermans]

Hi,
Is it possible to stack stacked files ?
I made a stack of 74 images last week and another onze last night of 120 images.
Is iT possible to stack these two again or do I need to start all over again using all 194 images ?
Same thing for the calibration frames.
Do flat frames need the exact same focussing as the lights or is an approximation enough ?
I noted the marks on the focusser at 6.8.
Thx for any feedback .
Eddy

[Warhen]

Eddy, If both stacks are good and adequate pixel rejection performed, you could simply add the two masters, or average them with greater weight to the 120 stack using PixelMath.

Regarding focus, ballpark should be sufficient. If the system is focused at infinity, and the majority of dust donuts are a few millimeters from the sensor, it should be fine!

[Eddy Timmermans]

I tried to clean the flip mirror on my dslr, so I suppose making flats now won't make a difference