M13

M13. I stretched the original Tif using DSS. Hardware details: Camera: Nikon D200. Telescope: SW Evostar 120 with Baader UHC-S filter. Mount: AZ-EQ6 guided using a ST80 synguider. Image details: Lights: 30 x 3min at ISO 800, Darks: 20 x 3min at ISO 800, Lights and darks separated by 1 min intervals. Flats: 40 x 1/40s at ISO 800, Bias: 30 x 1/8000 at ISO 100

Date of capture 05/03/2016. Conditions: Clear sky with moderate cloud, often interrupting the imaging. Seeing was ok (but target was quite high). The guiding seemed ok on the night but quite a few images showed slightly elongated stars :-(. Possible bad calibration (too aggressive). The wind was very light so that was not the issue.

Processing was done in DSS. I am trying to improve the handling of colour. I increased the saturation by 20% and aligned the colour channel histograms until the dark signal at the edge of the image (the darks were not quite cancelling the dark signal) was the same as in the original photos. This seems to work quite well (note to self!).