Comet Lovejoy/2014 close up.

[ChrisLX200]

Aquired last night Jan 16th 7:30pm, first chance at imaging for weeks! This is an LRGB 6 x 120s per channel, NP127is+0.8x reducer, Atik490EX.

ChrisH

[admin]

Wow... That's nothing short of spectacular. There's amazing detail in that tail!

How did you process this, if I may ask? Which tools did you find helpful?

[ChrisLX200]

Wow... That's nothing short of spectacular. There's amazing detail in that tail!

How did you process this, if I may ask? Which tools did you find helpful?

Thanks Ivo. It was a struggle I must admit, I'm not used to doing comets (my first!). To start with, each channel was processed seperately in terms of stretching, deconvolution, and noise reduction, and the stars were removed using the 'Heal' function. StarTools' mask selection got the stars OK even though they were all short streaks. I should have grown the mask a little more though. That left me with the 4 channels LRG and B containing a comet head, comet tail, and no Stars! A bit of head scratching later and I had to resort to PixInsight's 'DynamicAlignment' to register the comet head for each channel and these were then saved as registered files. Then I used the LRGB function of StarTools to composite the channels into a colour image and process as normal.

The problem with this very fast moving comet was the choice of imaging startegy, whether to go with LRGBLRGBLRGB etc., or LLLLRRRRGGGGBBBB etc. I figured if I went with the first option then each channel's exposure would be spread over the total exposure time, any detail would therefore be smeared. The problem with the second option was that, with the comet tail being a dynamic thing, there would be an issue with registration of the details in the tail (not the head of course). I went with the second option but that's why the tail is a bit of a rainbow of colours... You can see the real difference in the tail for each stack in the image below.

Perhaps a OSC camera would be better but there's no free lunch - the OSC is a lot less sensitive so longer exposures would be required. Tricky things to capture are comets!

ChrisH