CCDInspector vs MaxSelector

[SupernovaF1]

Hello all.

I have had some troubles in the last observing night with elongated stars. I think I have found what a couple of weak spots that I fixed (namely unprecise backfocus and both flattener and guidescope not very tight).

On the meantime I was having a play with CCDInspector and I was quite impressed by it, but even more impressed with its price.
I am convinced soon I will buy the PixInsight license after a very satisfactory trial, but on the meantime I decided to give Maxpilote's MaxSelector a try as it's now free.

I was surprised by seeing a significant different for the same picture. Not only in distribution but in curvature and tilt percentages as well. 
Does this match anyone else's experience? 

I think I will stick with MaxSelector as I will soon buy PixInsight (the FWHMEEccentricity script is good enough for quick check IMO).

Find an example  below. Its a 300" guided exposure with Red filter of the Elephants Trunk Nebula.
ZWO ASI 1600 MM-Pro & Altair x0.8 flattener/reducer & SW Evostar 80ED on a SW EQ6-R Pro.
Guiding error was ~1 arcsec. 

CCD Inspector

 

MaxSelector

 

 

See below a negative of the stars on the Absolute Bottom-Right corner magnified at 210%

 

And here the (much worse) Top-Right corner:

Edited November 22, 2020 by SupernovaF1

[han59]

It is pretty sharp image and full of stars. I'm interested to try it in the ASTAP inspector to compare. Can you share the full resolution in FITS format?

Han

 

[SupernovaF1]

Thanks @han59 Unfortunately, I think I have accidentally deleted them with MaxSelector!!
The same has occured with other set of pictures but thankfully I had a backup of those. Not sure how that happened to be honest. 

I repeated the same experiment with another set of pictures, this time M33. 

I have found that with CCDInspector, Tilt in Y axis has been greatly reduced from previous nights and the aberrations more concentrically distributed, which is encouraging.
The difference in tilt and curvature percentage is significant, plus the plot distribution. Thought it seems to be indicating that the periphery has indeed more curvature.

 

Edit: For completion here is the FWHM and eccentricity distribution in Pixinsight.
I used the same arcsecds per pixel in all 3 software: 1.63"/pixel for my SW 80ED with 0.8x flattener on a ZWO ASI 1600 (3.8microns pixel size)

 

Out of curiosity, repeated the CCDInspector plot for 10subframes.

And here the negative of M33:

 

This time the top left corner doesnt look as great (Zoom120%.)

 

And the bottom left very acceptable (Zoom120%)

I Attached the FITS file for thesubframe 001 (analysed above). Hope its helpful
Thanks!

 

M_33_Light_Blue_300_secs_2020-11-22T21-06-32_001.fits

Edited November 25, 2020 by SupernovaF1

[han59]

Thanks for the image. I have analysed it in (my) ASTAP using the same image orientation.

The values are difficult to compare. The average HFD is 6.6 or 10.8"which is comparable with the CCD inspector value. In ASTAP the tilt and curvature are expressed in delta HFD and not in %. The tilt is delta HFD 0.23 equals 0.12*1.63"=0.19". The curvature so the difference between center and outer areas is 0.7 HFD equals  1.12". The strange thing is that all stars are oval as also indicated by the PI image.  Must be optical imperfections.  The star ovality will skew the measurement.

 Maybe it is possible to partly correct by adjustment. The center is better then the out regions as indicated in the second plot but that is for any telescope.

Han

Later, I made a mod (not released yet) excluding the saturated stars. Saturated stars give a higher value then normal. The second plot indicates the worst corner is right top followed by left bottom, right bottom. Let top is the best.

HFD values for each star:

HFD

HFD plot. Darkest areas are the lowest HFD values. For each detected star one grayed area.

Edited November 27, 2020 by han59