Comet imaging simple trick

[NickH]

So..

1: Image the comet (e.g. Garradd) in the star field region (e.g. near to M71), using suitably shortish exposures to ensure the comet doesn't move too much during a single sub frame

2: Wait a night

3: Image the same star field, without the comet

4: Using software, subtract the starfield image from the starfield + comet image

5: This will leave mostly just the comet (some tweaking will be needed)

6: Use a median combine on the comet images to virtually remove the star trails from the comet image.

7: Blend and composite the comet back into the star field from night two.. having both images up (one sub of comet in starfield alongside your blend image) to ensure the comet is correctly positioned

[Dave]

Nice one Nick.

A great insight into how we could all get the most from our images.

Dave

[Freddie]

Doesn't DSS have options to do this in one go?

[NickH]

Most apps will do a dark subtract method on this, DSS's one stop shop doesn't work all that well, not when you want to stack and track on the comet and them composite it back in..

[martin_h]

Doesn't DSS have options to do this in one go?

Yes it does, but ive found the stars come out a bit soft...

http://stargazerslounge.com/imaging-widefield-special-events-comets/160081-comet-garradd.html

[NickH]

As I said...doesn't work "that" well.. :-)

It's an approach we're trying in reverse for images of the comet Elenin cloud with Faulkes. effectively trying to remove everything "but" the cloud...

[Dave]

I have had some success with DSS comet stacking and registering both stars and comet, but it produces very variable results.