CDD Inspector Help... What am I looking at?

[AndyUK]

I've been trying to pin down some collimation and focuser alignment issues over the last few weeks - First of all came collimation and then I managed to align the focuser (I think!). However, although I was much happier with the star shapes, I also wanted (want) to check the secondary for any slight rotation. I know that a collimation cap will help with this, but just over 2 weeks ago I downloaded a trial of CCD Inspector... and I thought I'd better try it out before the trial expires. So, using my last session image set I loaded them in and got these screenshots... but having done so, I find I don't know how to interpret them . Can anyone help, please?

1. Base Image Screenlist

2 - Field Curvature Map (1)

3 - Field Curvature Map (2)

4. Collimation vs Date/Time

5. Curvature vs Date/Time

6. X Tilt vs Date/Time

7. Y Tilt vs Date/Time

8. Vignetting

I'm sure these are all telling me something and there's something I need to adjust (the vignetting graph and colour gradients on the curvature maps are a bit of a giveaway?), but it would be very useful if I knew exactly what I should be concentrating on adjusting and what these should look like if everything was adjusted correctly...

(Thanks!)

[MartinB]

CCD is a great tool but it should come with a health warning, if in doubt compare what the data is telling you with what you see in the subs to decide whether the data provided by CCD is a concern or not.

You have a nice flat field and this amount of tilt isn't going to cause any problems with your images. In my experience anything through to turquoise is ok.

Your collimation error is reasonably small and I would stick with it rather than starting to make trickier collimation adjustments to the MakNewt, you could well end up worse off.

You can be happy with these results.

CCD inspector is a very useful tool for monitoring what is happening with your subs, esp for deciding if a focus adjustment is necessary. The FWHM monitor will present a graph of data for each sub so that you can soon see if the focus is drifting off.

Measuring all you subs in CCDI is also useful to help you home in on subs to reject.

[AndyUK]

Thank you very much Martin - You don't know what a relief that is to me (or perhaps you probably do!). I think I was expecting to see more of a "classic" gradient on the curvature field maps (with central point darker than edges) and to see the curve on the Vignetting graph more even, ie spanning -100 to 100...

However, as you're saying that I can be happy with these results, then I'm VERY happy...!