Comet Lulin
Comet Lulin
Comet Lulin, a LRGB picture taken with Canon 20Da, ISO800 and WO FLT-110 without field flattener for FLT used. Total exposure time ~ 90min. Dark and flat frames used. Filter: 2" IDAS LPS. Guide via Meade 16" LX200ACF, FR3.3 and DSI-II Camera. Picture taken 27/28-Febr-09.
The BG layer consist of 5 pictures: 5*30sec which are tracked on the comet kernel and which are aligned and stacked (average combined) on stars. The FG, comet layer, consist of 38 pictures: 10*60sec; 12*120sec; 15*180sec; 1*600sec; which are tracked on the comet kernel and which are aligned and stacked (median combined) also on the comet kernel.
Median combine remove the star tracks. The FG, comet layer is then masked together with the BG layer via APS CS4; thereby integrating the best/relevant information from the two layers.

Published versions in S&T archive,
http://media.skyandtelescope.com/images/Lulin-FinalMIX-LRGB-1000.jpg
http://media.skyandtelescope.com/images/Lulin-LUM25_RGB-BG30-1000-SR.jpg
Comet Lulin.