|
Flat calibration with 1.25 filters
Hi
used sky flats and bias to calibrate a single sky flat taken at a different time from the calibration flats.
without flat calibration, there was 30% drop from the centre to the darkest corner (right hand image below). After calibration, the test image was flat to better than 1%. The noise was (naturally) greater in the darker corners, but not excessive.
At f4, I can live with the 1.25 filters - but they work best if they are as close as possible to the chip.
|