Collimating my 200p

[Hypernova]

I had my scope checked last night while at the local astro club meeting and the laser collimator this guy was using suggested that my scope was off in it's collimation. They offered to help collimate it next time round but the next meeting is in a months time so I thought I might have a crack at it myself. I've had a look through astro baby's guide and have a couple of questions, which is the best type of collimator to buy, astro baby used a cheshire but the people at the astro club told me to just buy a laser instead also what kind of tools do I need? The scope is a 200p dob.

[John]

The problem is that laser collimators themselves need to be in good collimation to be accurate - many are not so show false results. The best test is on a star - defocuss the star a little and it should turn into a doughnut shape (ring doughnut !) with the dark shadow of the secondary mirror in the middle. If the secondary shadow is right in the centre then the collimation is good, if it's off a bit to one side or another then collimation adjustments are needed. Because of the issue with innaccurate laser collimators a non-laser cheshire eyepiece is often the best tool.