Removing or Lessening Star Trails

[jdonald]

I have PI 1.8, crashes a lot in Color Saturation but thats a different issue.  I find myself using CS6 a lot more because of the plethora of tools in PI I have no idea what each does. 

What I want to do is fix minor trailing in my image, all I need to do is shift it 1 or 2 pixels, how do I accomplish this in PI?  Or what tool in PI do I play with?  My guess is starmask to start but I am lost from there.  Maybe something in MT?

This is the image in question:


M35_ISO1600_40x120s_1hr20m by AstroJeff, on Flickr

Thanks,
Jeff

[Carlos Milovic]

If the image is still in the linear stage, you may try to use the deconvolution process. Use the DynamicPSF process to create a synthetic PSF that matches the trailing of your stars, and then load that PSF as an external image in the deconvolution process window.
The MT process is another alternative. Just draw a line that matches the drift. Since this is hard to do for small drifts and non orthogonal angles, try using more than one way (ways are an option in MT), so the averaged line resembles more your drift. Other than that, just play with the settings. Try small amounts and several iterations, or large amounts and just one iteration.
You may use the StarMask to protect other objects or very faint stars. Also there are two threshold parameters in the MT process that may help.

[jdonald]

Thanks Carlos, I was playing around with the MT tool and this is what I came up with:


M35_ISO1600_40x120s_1hr20m1-Noels by AstroJeff, on Flickr

Is it better?  I used erosion and a 2 box diagonal in the direction of the trailing.  I kind of see bubble artifacts but not sure if I am just seeing things or not.

[Carlos Milovic]

Did you use the Erosion operator? There are some strange haloes around some stars... try a smaller amount, and also try ATrousWavelets to sharpen a bit the stars. You may try iterations between MT and ATW to achieve a better result. Try to be conservative, and prevent artefacts.

[jdonald]

What do you think of this? Make sure to go into lightbox mode to really see the details:


M35_ISO1600_40x120s_1hr20m by AstroJeff, on Flickr