Quote:
Originally Posted by BruceG
Hi all, I was helping a good friend with his new RC8 on Monday evening and we found the first images not as amazing as we were expecting.
Below are the first images left to right tarantula with a CLS clip filter (taken from a very LP affected site), 10x90 sec subs and only a few darks with a spectrum modified 450D at 1600 ISO, the same target with Ha filter with 180 sec subs firstly in colour and then the same data in B&W, Finally an enlarged section of the first image to show the bloated stars with red and blue fringing.
He is using the Orion 50mm mini guide scope and starshoot autoguider camera. The focal length of the guide scope is 145mm and the RC8 is I believe 1600mm. Do you think the issue is poor guiding with the guide errors causing the fat stars or do you think it is an optical issue? The PHD2 graph was not too good and PA could also be improved.
Any insights or steps to investigate the issue will be greatly appreciated.
Bruce.
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GSO+Canon - 0.66 arcsec per pixel (ASP).
Miniguide+SSAG - 6.7 ASP
6.7/0.66=10.15
That's about the edge of the envelope. You should look for a ratio under 10. If it was a mono chip instead of a DSLR you could bin it 2x2 which would help a lot.
If the PHD graph (measure in ASP) is bumpy you need to improve the mount alignment. You didn't say what the mount was. That could be important too.