Treatment of comets

[-Amenophis-]

Hello,

I'm trying to image comet C / 2017 S3 using my CCD G2-4000.

This is a first for me because I do not know what to start at the technical level of shooting.
Although the comet is low on the horizon and I shot at 4:00 am (dawn was present). I tried to shoot to get out the first difficulties and the first questions.


  - The tracking is done on a star? or on the comet?

  - The exposure time ??


I left on a tracking on a star and 300s of pose.

So here is 1 pose of 300s in Luminance (without treatment).



I did the same with each RGB color layer.


From what I understood there are 2 alignments to be done (separately) to get an image of the comet with punctual stars.


  - Alignment on the stars

  - Alignments on the comets

 
Mix both to get the final picture.


So, I did both alignments. Left alignment on the comet and right on the stars (do not look at the image processing but just the shape):



I can not go further.

I think that it would have been necessary to make a complete shoot LRVB but making the autoguiding on the comet, not on a star.

So next night, I'll try:


  - Sidereal tracking: LRVB 300s for the stars

  - Comet Tracking: LRVB 300s for Comet


What do you think ? How do you shoot? and tracking ?

Thank you very much for your help.

Thomas

[pfile]

tony cook is pretty good at comet processing and he has written a tutorial here:

https://www.astrobin.com/151422/?nc=all

rob

[-Amenophis-]

Thank you but it's for digital camera...
it's the same for CCD and each filter ?

[Terestron]

I am having a issue understanding how to combine as well. I am shooting using a Mono CCD.  I took R, G, and B subs about 5 ea.

I must be missing a step, when I do combine I get a elongated comet that starts out blue and ends with red.  I am not grasping the work flow for combining the RGB subs.

From the tutorials it looks like they are starting out with a RGB image already. 

Can some one give me the work flow for R, G , and B subs? 

[pfile]

well, generally speaking you need to prepare 2 images; one that's registered on the stars, with the comet rejected thru pixel rejection in ImageIntegration, and another that's registered on the comet. there's a process called CometAlignment that will do that - you mark the start and end positions of the comet (in the first and last frames) and then based on the interval between frames the process interpolates the comet position, thus determining an X-Y offset for each frame. when you integrate these frames, you need to reject the stars as outliers.

then you have to combine the star master and the comet master together. this plus the rejection settings are the topic of tony's tutorials.

as for OSC verses mono+filters, i don't think that changes much - you need to load them all into CometAlignment and identify the comet positions. then i suppose you should integrate only images from each filter together and then eventually combine those images into a single RGB image of just the comet, and proceed as though you were using an OSC.

rob