Horsehead gone weird, help needed!

[ian straton]

Anyone know what has gone wrong here?

This is a stack of 20x5 minute exposures at iso 400.  The processing has been done purely in pixinsight.  I ran the sub frames through the blink comparator to get rid of gross aberrations,  then through the subframe selector script to check for good quality frames and basically selected the 20 best frames in terms of star shape eccentricity and fwhm having done that I ran the remaining frames through star alignment and image integration and this is the result. 

The stars are these odd bow tie shapes... now each sub frame is pretty good in terms of tracking but there is overall quite a bit of movement between the first and last frames which if you traced it out would be pretty similar to this shape but I would have expected the star alignment to have removed this?

I have used no calibration just the light files. the star alignment Interpolation was left at the default settings of Auto / 0.30 clamping threshold.  Rejection method was Winsorized Sigma Clipping, sigma low was 4.0 high 3.0 (again default settings)..

[ian straton]

and a similar issue with m101 although in this case the tracking error was linear and as you can see the end result looks like the registration process hasn't recorded any translations for the frames?

[pfile]

sometimes with uncalibrated DSLR files, there are so many hot pixels that starAlignment sees only those pixels, interpreting them as stars... and since they are all in the same place on every frame, the alignment is a no-op.

so try re-aligning your files, but look in the star detection section of StarAlignment and increase the noise scales / hot pixel rejection and see what happens. when you look at the console as SA as running you should see some real dX and dY values instead of just a bunch of dx=dy=0...

rob