Quote:
Originally Posted by barx1963
I could be wrong but if there is a built in barlow in the focuser drawtube, wouldn't that get in the way of the cheshire? At least it would with my cheshire!
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Even if the built-in barlow gets in the way, a cheshire eyepiece would work brilliantly in Mick's larger scope.
There is another way,
, always is, isn't there. It involves getting your hands on one of the old Kodak film canisters with its cap in place. If you make two holes, about 3 - 4mm in diameter, smack bang in the middle of the cap and the base of the canister, slip it into the focuser (it happens to be exactly 1.25"!), you've got yourself a very rudimentary collimator. It will work brilliantly for the positioning of the secondary mirror (it's what I use with my 17.5" dob), but its primary mirror collimating capability isn't as good as it doesn't have the crosshairs, but it will still do a significant improvement on what you've got. What a laser will improve upon from a cheshire or the "canister method", is splitting hairs. Very good though if you've got one, which I use too.
There are several sites that give very good instructions on collimating newtonians with cheshire's. Do a google search on "collimating a newtonian",
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