Collimating a GSO RC8

[Carl]

Astronomy Technologies recommend the use of the Cheshire 1.25" collimation eyepeice for collimating the 8" RC Astrograph.

I've seen them for around $30-$40 in OZ and online, the price sound a little cheap. Will this collimator be accurate enough for astro imaging or is there a better mid priced alternative that wont break the bank?

Regards
Carl Rainer

[Paul Haese]

I wouldn't just use this Carl. I think the better option is to collimate while the imaging camera is in place. Making sure to re-center after each adjustment. The collimator might get you close but not perfect.

[Tandum]

If you typed your question into google you would have found Moon's website and his procedure (http://deepspaceplace.com/gso8rccollimate.php) which works fine..

[yusbot]

do you know how did he get the blue screen with the crosshair in it?
what program is used?

[glend]

Carl your entering an area of possible frustration, as the RCs are not like newts that can be straight forward to collimate. As a RC08 owner that is still learning I can offer a few pointers:

Do not try to adjust the primary, this can get you into a cycle that leads to making it worse. The Cheshire can be used, but a good laser collimated (which has been collimated itself and verified on a bench test, is very useful. There are many online tutorials on collimating RC08s and you coukd also download and print the Astro-tech RC08 manual. Astro-tech and GSO are the same scope.

Good luck.

[SamD]

I've had an RC8 for a bit over a year now. My basic Cheshire eyepiece is useful to get collimation good enough for deep sky imaging (ie nebulae/clusters). My Cheshire eyepiece seems to be at least as good as or more accurate than using the LiveView method. As long as collimation is quite close to perfect, I find that in practice, seeing is the dominant contributor to star FWHM, and that any eggy stars are down to bad tracking, not collimation.

The only thing I've needed more accurate collimation for is planetary imaging (using a 3x barlow). For this, I've found that a Cheshire eyepiece alone is not really accurate enough. Instead I use MetaGuide to make the final tweaks to the secondary with my imaging webcam and barlow in place. It was a bit of a struggle to get used to using MetaGuide at first, but it now seems a fairly quick and reliable method.

The good news it that my (carbon) RC8 seems to hold collimation pretty well, which is one less obstacle to good imaging.

[SamD]

Whoops, the original collimation question from Carl is ancient !


CCDInspector by CCDWare does field curvature maps based on star profile analysis across the field