Pixinsight Comet Alignment function ?

[MikeODay]

I posted the following question on the Pixinsight site but no response so far - I was hoping that someone here might be able to help ...

http://pixinsight.com/forum/index.php?topic=3980.msg61766#msg61766

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How do I stop Comet Alignment Tool wasting large sections of the sub-images?

The problem:

I have a stack of 186 sub-images of comet 252P that was moving very fast. 

The images are 6016x4016 pixels.   

In image #1 the comet is at 3140,1085  and in #186 it is at 2665,2555.

That is, the comet has moved -475 pixels in X direction and 1470 in y direction.  As such, I would have liked the resultant stacked image to be larger than the individual subs at (6016+475)x(4016x1470) with the center of the comet at (2665-475/2),(1085+1470/2).  I would then crop the center (6016x4016) of the image as necessary and re-combine it with the star aligned image.

Alas, I end up with a stacked comet image that is the same dimensions as the sub, the comet in the location of image #1 and all of those extra pixels above the comet in the later subs cropped away by the tool.

Attached is an example of one of the subs that has been re-aligned with significant loss of information.

Does anyone know how I can force the tool (or another tool) to align the subs without cropping the information in the subs (ie. by enlarging the canvas to allow the alignment to proceed whilst retaining all of the information in the subs).
 

 

Here are more image that show the problem ...

1. star alignment showing incomplete removal of comet path through the centre of the image.

2. resultant comet aligned image

3. simulation of how the final image might look with the current comet aligned image (what I don't want); and

4. simulation of where I want the comet to appear in the final image (with all the information above the comet retained (which currently is not))

Any ideas on how I can achieve it would be greatly appreciated.

Cheers
mike

[MattJenko]

Can't you just use the Comet align method from Harry's site but ensure that the end image you choose is in the location where you want the comet to be?

[wimvb]

I've never used it, but Image Integration in PI has a frame adaption option. Have you tested this?

I would guess that treating the stacking as a mosaic would create a larger final image that you then can crop

Something like this in DSS:

 

Or am I just rambling?

[StuartJPP]

PI's comet alignment assumes that there are no dropped frames in the sequence and that nothing moved except the comet.

I find that this isn't always the case so I will use the comet align/stacking to produce multiple stacks that are spaced equally apart and then stack those images.

I'd prefer it if you could select the comet on each frame, though you can do in the old comet stacking function.

Comet processing can be a bit of a chore to get everything working properly.

[MikeODay]

Thanks guys for all your help and suggestions.

The problem is that the StarAlignment and CometAlignment tools in Pixinsight do not enlarge the canvas to accommodate all of the subs.. This means that if the stars are moving (due to poor tracking for instance) or, as in my case, there is a fast moving object, then the canvas size remains the same while the images are progressively aligned so that they 'fall off' the canvas.. (please note that the FrameAdaptation option in the Comet Alignment tool seems to relate to image intensity rather than image size).

The solution was to first use the Pixinsight Crop tool to enlarge the canvas size of each sub by an amount equivalent to the number of pixels in X and Y directions that the comet moved between the 1st and last subs.. I then applied the CometAlignment tool to these enlarged sub images..  

Here is the result I achieved ...

 

Cheers

Mike

[Scooot]

Maybe you could use the FFT registration script, you can choose which sub you use as the reference frame? You'd still end up with one aligned image but at least you could pick which one. I use this to stack my moon images taken with my dob on my EQ platform with which I always get a little bit of drift across the fov.

[MikeODay]

Thanks Richard.  Using the Crop tool worked for me.  Does the FFT script enlarge the canvas to fit all subs?

 

Cheers

Mike

[Scooot]

8 minutes ago, mike005 said:

Thanks Richard.  Using the Crop tool worked for me.  Does the FFT script enlarge the canvas to fit all subs?

 

Cheers

Mike

I don't know for sure but I don't think so. The resulting image looks to be the same size as each individual sub.

[MikeODay]

Thanks Richard.

Cheers

Mike