Cheshire Collimation

[Rakanishu]

Just a few questions on using only a cheshire to collimate my skywatcher 200p (is it possible with just the cheshire or do i need a small film canister with a hole drilled inside?)

Also throughout collimation should the focuser be fully extended or wound all the way in? Does it matter at all?

Thanks

[valleyman]

You dont need a film canister, and the focuser should be right in

[Rakanishu]

Thanks Valleyman

[Ganymede12]

That's handy for me too because I picked my 200P up yesterday! Thanks!

[umadog]

Just a few questions on using only a cheshire to collimate my skywatcher 200p (is it possible with just the cheshire or do i need a small film canister with a hole drilled inside?)

If the film canister also had a reflective inner surface then it would, in fact, be a Cheshire. Such a tool would be used to adjust primary tilt. What is typically called a Cheshire is a combination tool comprised of a sight-tube (the long bit with the cross-hairs) that is for secondary tilt and a Cheshire (that is reflective and does primary tilt). See images: http://www.physiol.o...tionLinks.shtml

EDIT: so if you have the combo tool you have the film canister.

Also throughout collimation should the focuser be fully extended or wound all the way in? Does it matter at all?

Most focusers aren't perfect and change slightly in tilt as you rack in and out. As a consequence, it makes the most sense to collimate with the focuser racked to roughly where your high-power eyepieces come into focus. It's at high powers where you'll notice misscollimation most. Collimating the fully extended or fully retracted positions may lead to unusual focuser tilts as the tube is often touching a stopper at those positions.

[sam mayo]

this is handy getting a chesire nxt week

[Moonshane]

what Umadog said.

also I tend to alternate thumb screws so the 2" is opposite the 1.25". I feel this evens them out more centrally. broadly try and replicate what the scope is like in use as this is where the eyepieces will actually be.

[pat]

On the comment about the focuser rocking. I find a sweet area where the focuser doesn't rock. Poistion rubber rings on the eyepiece barrel. So when the eyepiece is focused it is within that area or space. Pat