Further to my
previous thread here, I have bitten the bullet and swapped out the focuser on my FSQ106 with a new FTF3515 from Feather Touch. A very nice piece of hardware it is (if a tad expensive!). The improvement in the data quality is huge with what now appears to be a nice flat field as measured by the tools in Pixinsight and examined visually.
I am, however, still having difficulties with star alignment when registering the images taken either side of the meridian so there is definitely something awry with the data. I've tried RegiStar and Pixinsight and both give me the same (bad) results. That is that the bright stars do not quite line up in the registered images. Blinking back and forth shows the bright stars to be not aligned. If I take this data through the full image integration and channel combination process I know that I will finish up with coloured flares around the stars which is not good.
There is a
link here to a Dropbox folder which contains pre and post meridian flip images. I have saved the raw and calibrated subs in *.fits format and *.xisf format.
The attached images show the output from the aberration inspector script and the FWHM eccentricity script in Pixinsight. These indicate that the data is clean and the field is relatively flat with no obvious tilt or field curvature. If I take the time to peer very intently at the brighter stars in the images I can maybe see some slight elongation that is different in the pre and post flip images but it is very small and I am needing to zoom in to 200% to pick anything. At the end of the day though, there is something in this data which is causing the brighter stars in a registered image to not line up.
I'm working on the assumption that I may still have some residual tilt that my eye and the PI tools are not picking up. This being the case, I would like to hand over this data to my learned colleagues on this forum to see if anyone wants to forensically analyze this data and see what can be found.
Thanks for looking,
Rodney