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M51 with PD Camera 31/1/2015

Roger Samworth


Today I am re-sending an image I sent last week, but I am still a bit blown away by the fact that the PD video camera managed to capture such structure in M51

M51 is a bit special because of Lord Rosse's observation in the 1800s, of course. Rosse's drawing of M51 was the first occasion on which a spiral form was recognized in a nebula. The drawing was made in April 1845, and circulated at the June meeting of the British Association for the Advancement of Science. Bear in mind that it was done with his 72" reflector!


I thought it might be interesting for the Group to see the stages I went through to get the final image - although by no means do I pretend to be an expert imager!


a) is a raw single frame from the PD camera. The camera internally has stacked 1024 1/50th sec. frames to get this.

b) is 9 of these frames stacked in Registax5 (I usually prefer Registax5 to 6), and a dark frame subtracted.

c)  is the image processed in Registax, then cropped, flipped vertically to get the orientation right and re-sized.

d) is with the image similarly processed using GIMP2 (a freebee image processing package)

e) is with the image procesed in Registax plus a bit of tweaking in GIMP.


Which of the processed images is better is somewhat subjective.




Pictures below are same as those above accessed via links:

m51 Rosse sketch
Rosse 72 inch telescope
a m51 raw camera
b m51 registax5 9 stack
c m51 registax5 processed
d  m51 gimp processed
e m51 registax5 and gimp processed
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