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Subject
M31
Date
October 2003
Telescope or Lens
Vixen ED102SS
Mount
GP DX
Camera
SXV H9
Filters
TT RGB and NIR blocker
Total Exposures L 5hrs 40 min R 80 min G 80 min B 80 min
Sub exposure
8 Frames each 2 x 20 min
8 frames each 1 x 10 min
8 frames each 1 x 10 min
8 frames each 1 x 10 min
Binning
Luminance 1x1 RGB 2x2
Field of view and resolution
Approx 1.2 x 1.75 Degrees. 2 Arcsec / Pixel
Comments  
This mosaic of the Andromeda galaxy, M31 was imaged over several sessions between the beginning of October and December 2003. It comprises of 8 frames and a total exposure time of 9 hours 40 minutes. I do not feel that this effort is as good as the Veil Nebula mosaic. I had some difficulty getting the data for this image due to bad weather, work and local light pollution from a nearby golf driving range that does not turn off its lights until 20:30. When I gathered the Luminance data, M31 was well positioned from my location meaning that I could get a couple of frames per session before it got too low. The colour was a different matter. Bad weather and the march of time meant that I had to take 10 minute exposures so that I could get the RGB data while M31 was still reasonably high. The short colour exposures coupled with some slightly hazy skies and gradually lower position means that there were some significant gradients to deal with. I could not get as good a match as I would have liked and there is some evidence in the top left corner of a join that I just could not shift. There are also some differences at the lower right. Moral of the story (stating the obvious) is to take longer exposures if possible and try to get the best images with respect to position, light pollution and sky conditions, or at least try to minimise the difference between frames. It is easier to eliminate gradients that are unavoidable if you have better data to work with. Processing was with Astroart for basic calibration and RGB combining. The mosaic was compiled in Adobe Photoshop with the colour and luminance done separately and then combining the finished luminance and RGB images.