Cheshire eyepiece and RC 8"

[The universal]

hello great wise ones,

I've had my fill of reading today so I thought I'd ask a specific question.

no instructions came with my scope so after googling I've found a PDF for the astrotech rc

it advises to use a cheshire eyepiece to collimate.

so far so good, have the eyepiece in and everything looks good. the black dot is in the centre of the bright disc which is surrounded by perfectly concentric rings, however, the physical brass crosshairs in the cheshire are close but do not line up perfectly with the central black dot, and the central black dot is not bang on in the black ring that is physically stuck to the secondary mirror

the astrotech PDF doesn't mention the cheshire crosshairs and it also doesn't mention the black ring that is stuck to to secondary. it just says to centre the black dot in the bright disc while making sure everything else is concentric.

I'm dying to check out a real star but that isn't looking likely tonight

any words of wisdom

[Leveye]

[richyrich_one]

Hi

Just collimated my dob and I was puzzled by the cross hairs being out of focus.

What you are looking for though is the RELECTION of the cross hairs in the mirror which should be clear and sharp. Line that up with the centre spot on the primary and you should be good.

What I found useful was to make sure that the cheshire was rotated so that the cross hairs are oriented differently to the spider vanes so you know what you are looking at.

Recommend reading this: www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

[The universal]

thanks for the advice, really appreciate it