Setting up the exposures

Next comes setting up the exposure sequence which includes the type of exposure ie, dark frame, flat frame, light frame or bias frame. This is set to light frame, then the filter that is being used so I set this to Ha (this puts the letters Ha in the file name so that they are easily recognisable later). The exposure settings can be set to incorporate several filters to run one after the other but since I do mainly narrowband with exposures in excess of 10 minutes I usually only do one filter a night before the subject is too low in the sky. I set an exposure time in seconds which for the image here is 1200 seconds or 20 minutes and the binning mode which is 1x1, finally the number of exposures which for this image of IC443 is 12. Also in this dialogue box is a delay between exposure setting, this I set to 60 seconds toi allow for the guiding camera and mount to settle back down after 'dithering' (a system by which the guide camera moves the mount a certain amount of pixels in a random direction after each exposure---this is used to help counteract any chip defects, hot pixels, etc when stacking and combining the  sub frames), under options I set dithering via guider to 'on'. Once this is done I go back to the sequence tab and click 'start' and now the waiting begins, 20 minutes can seem like a lifetime while you are waiting for the first sub frame to download and keeping an eye out for the weather.