Refractor Collimation

I am trying to collimate a 6 inch achromatic refractor (has adjusting screws at the objective). I've been trying to use stars, but seeing hasn't been great (or my optics are terrible). Trying to use a star at zenith to improve seeing makes it impossible to get at the adjusting screws without a ladder. I've read about people using a cheshire eyepiece to collimate a refractor. Will this yeild a good collimation, or is it akin to a "rough" eyeballing on a newt? Can a laser collimator be used? How? Any recommendations on what type brand (cost is somewhat a factor). Any info or links appreciated.

Also, I am not sure if the focuser assembly is dead on. Question: If an object is centered in the EP while using a diagonal ($99 WO - love it), and the diagonal is rotated about the axis of the scope in the fosuser, should the object stay centered or is it expected to move? Objects move significantly in mine, at high power, they can move outside the field of view. Intuitively, I believe it should stay centered. The only explanation I can think of is that the focuser and/or diagonal are out of alignment with the objective light path (in which case, I guess all attempted collimation is kind of futile).

Comments or advice appreciated.

Thanks.

Alignment is quite easy with a Cheshire eyepiece, especially on a bright, sunny day. Put a cover over the lens. Put the Cheshire in the focuser without a diagonal. Aim the 45 degree reflective surface of the Cheshire at the bright, blue sky (away from the Sun, please!). If you look through the Chesire you will see some reflections. They shold all be nice and concentric. If not, adjust the lens until they are. Most achromats are corrected for coma, so careful alignment with the Cheshire should be all you need.

Tony & Alan:

Thank you. I found the older thread. Great help.

I'm guessing, square the fouser first, then collimate?