Collimating

[Joesdob]

Hi I just recently joined the group. I have been into astronomy for quite some time and finally took the leap and purchased an Orion XT8 Dobsonian. I know collimating is a very important part of this and I was hoping I could bring it to someone and you teach me how to do it in person? The videos on YouTube can be confusing and after spending the money if someone would be willing to show me how it would be greatly appreciated! Thank you in advance for your responses.

[SEmert]

Hi Joe, welcome to the group. I'm sure many of us can help out. I can volunteer, but I'm sort of on the wrong end of town for you (NE corner of the Cities, in White Bear Lake), so unless someone closes reaches out, just send me a PM and we can figure out when and where to link up.

Do you have any of the collimation tools yet? Typical you need a laser collimator, and a sight tube/cheshire is also good to have. Also, for the laser either one that has the Barlowed laser collimator adapter or if you have a Barlow lens that can be adapted to the purpose, a target mask can be made for essentially no cost. If the YouTube videos didn't point it out, Barlowed laser collimation increases accuracy of collimation using a laser collimator by a large percentage.

[BradNasset]

Welcome! Attached is a graphic I made some time ago that might help. Nothing to be afraid of.

Generally the secondary is pretty close when new. Here is a pretty basic method for the secondary: Get your eye in the center of the eyepiece hole, and see if the mirror looks centered. Often you might be able to see the three little clips holding the mirror in place. If in doubt just leave it alone- better to be close enough than mess it up. This is a bit trickier than the primary mirror- the three adjustment screws put pressure on a "center bolt" so if you loosen one screw you just need to tighten one or two of the other screws. (think of 1/8 turns or less for adjustments) The secondary mirror collimation is likely ok from factory. (Plenty good enough to get started)

Next, to collimate the primary mirror, point the scope at a bright star, and dial the star in and out of focus- back and forth. If the fuzzy bands around the star are oblong like an egg, loosen all three of the lock screws, then fiddle around adjusting the mirror (one screw at a time, maybe 1/8 or 1/4 turn) until the fuzzy rings are round and the star is in the center of a perfectly round donut. You are now collimated! Start low power, then go up a bit for fine tuning.

Steve has the real-deal plan, but this may get you started.

[Joesdob]

Thank you!!

[Joesdob]

Thank you!!