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David,
I image in 3 colors, almost necessary given that Jupiter at my latitude
is not getting any higher than 43 deg. I collimate in red, not just
because of minimizing the turbulence, but the atmospheric dispersion
separates the colors so much at 35 deg that a white image is a mini-rainbow, almost impossible to collimate in average seeing. One should collimate an SCT at an approximate elevation one does imaging. Your dob probably is not so particular as you dont have mirror flop. SCT's are a nice
engineering compromise, but a newtonian should give better images in general.
People have had problems squaring up their cameras, especially if the 1.25
barrel is undersized. A single layer of thin tape solved that issue for me.
The last thing I do before inserting the camera is check collimation with a
short fl eyepiece. Any tilt would of course have focus implications. Probably as important, the ccd should be at the same 'center' you were collimating. On my setup the planet on CCD is no more than 30" away from my crosshairs.
Indeed at low elevations, the RGB shift in Registax is necessary for color ccd's. However if separated out into 3 colors, Maxim DL's align will automatically zero out the dispersion.
I'm glad the exp PSF is working for you. Any telescope with a central obstruction will see the airy disk fall off faster than a gaussian. The Maxim DL exp is not as sharp a singularity as posted by janoskiss, but the profile needs to be determined -- at some point when I have time, I'll plot it out.
On some images the gaussian will be better. It's a strange thing, but night to night an image will yield to a different method. Some images like VC decon for reasons that are a mystery to me. It will take a lifetime to figure all this out!
I'm going out now to set up. Temperature here is 109F (43C) even as the sun is setting! I'm not sure the optics were designed for this!
Glenn Jolly
Arizona, USA
My usual image train:
C11 / JMI NGF-CM / 3x Meade imagemate / Sirius RGB filter wheel / DMK 21BF04
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