Starlight Xpress SXVF-H36 - Manual (Page 12)

Handbook for the SXVF-H36 Issue 1 August 2007
12
Warm pixels in a small portion of the raw image
The isolated nature of the warm pixels in an SXVF-H36 image permits you to use
several different methods of removing them from your raw images. Subtracting a dark
frame is the most commonly used means of removing the warm pixels, but is not
necessarily the best or most effective method. This is because of the increase in
readout noise that dark frame subtraction entails and the need to accurately match
your darks to the light image. If you average many dark frames together to create a
‘master dark’ the readout noise will be much reduced (by the square root of the
number of averaged darks) and so this is one way to improve the situation, but it
needs a lot of imaging time to be devoted to gathering the required dark frames. Some
software (such as Maxim DL) has the ability to scale dark frames to match your light
frames accurately, without the need to have equal exposure times, so a ‘library master
dark’ can be used many times over and this will save you much time. The SX
software does not currently do this, but you can subtract a matched dark frame by
using the ‘Merge’ option.