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On Tuesday night/Wednesday morning I took my first shot with my new ASI2600MC Pro through a Vixen SD81 with a dedicated flattener and reducer. This is the result. https://www.astrobin.com/7lbfzq/#share-modal Most importantly, I'm delighted with it. That's what counts. I'd like to learn more though, so I've looked at a random individual frame using Pixinsight Abberation Inspector, and it shows this.  The same process on the stacked image shows this...  To my eyes, the stars in the top left and top right seem to be pointing away from the centre, but the stars in the bottom corners look ok. Is that tilt? I then converted to greyscale, and ran FWHMEccentricity thing on a single frame (I'd read if you'd had a merdian flip, this would be best) and got these maps...   To me, they just look like rainfall maps for where I live. Anything obvious I could do to improve things or should I just leave well alone?! The main reason I ask is the ambiguity about the spacing distance required by the flattener/reducer. Vixen say one thing, their diagrams say another! If that was wrong though, I'd expect the stars to stretch in all the corners. I am, however, dim. Thanks for looking. |
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| Another option for detecting tilt is ASTAP (Astrometric STAcking Program). There is a function in the Tool menu called CCD Inspector that computes a tilt map for you. The results I have gotten from it personally have anecdotally correlated to what I think I can see visually. I admit I also have never quite understood PixInsight's eccentricity maps either. |
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| THere is slight tilt toward the left side, which can be corrected by adjusting the tilt corrector on the ASI camera. A slight increase in spacing might also be adviseable, to the tune of 0.1-0.2 mm. |
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| Thanks both. I guess adjusting it depends entirely on the orientation of the camera to the scope. I’ve been fiddling this afternoon so everything is in a different configuration. I’ll take another look next time but things should be more standardised now! |
