Collimation

[PSALM19.1]

Hi, anyone prefer one type of collimator over another? Thinking of an Orion laser from Bintel for my 8" dob. :question:

[AG Hybrid]

A laser collimator is fine. As long as the laser in the collimator is...collimated. Most will swear by a sight tube with cross hairs. This is called a Cheshire eyepiece. Both are relatively affordable options. You can jury rig your own sight tube with a eyepiece cap and small hole in the center. Works alright too.
Tutorials can be found around the web.

If your willing to spend more money there are options. I use a 2" Hotech Laser collimator and its fantastic. About 30-40% more expensive then your standard laser collimator though. There are more options again that people will swear by however. I'll let them try and justify purchasing a $300+ collimator, because I cant.

[glend]

The GSO laser collimator can be collimated itself (it has axis adjustment screws). Some laser collimators cannot be adjusted, better check with the supplier before you buy one. There is an Article in the Projects and Articles section on how to collimate your laser collimator - worth reading and doing.

It's pretty simple, just make a small jig to hold the collimation tube (can be as simple as four nails arranged in a criss-cross cradle in a a small board), and aim it at a target about 5 metres away and mark the spot on a target piece of paper then rotate the collimator tube about 90 degrees in the jig and mark again and so on as you turn it in a circle on the jig. If the spot doesn't wary much (say they are all in a 10-15mm circle) then consider it good enough. the smaller the grouping the better. If they are outside of that boundary you can adjust the laser with the screws on the unit and try again.

[barx1963]

Technically ( as I understand it) a Cheshire includes a 45deg cutout, as opposed to a sight tube that is simply a tube with a hole at one end and crosshairs at the other. Most Cheshires (eg http://www.bintel.com.au/Accessories/Collimation/Orion-Collimating-Eyepiece/418/productview.aspx ) incorporate a sight tube as well.

A good guide to collimation I have ised is here http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide .htm This is a small Newtonion done without a laser.
On my scopes I always noticed that the best results were achieved using a Sight Tube/ Cheshire but to check it each time I used a laser.
Cheaper lasers are often out. My old GSO one was fine in my old 12" but in the 20" produce a noticeable error compared to the cheshire. I now have a Howie Glatter one and it is lovely, bit exxy but!

Malcolm

[Asterix2020]

I just received my CatsEye Collimator Set today. Very interesting going through it all. The problem with laser collimators is they can indicate the scope is collimated when it's not. Have a look at http://www.catseyecollimation.com/, especially the information down the bottom left of the page (scroll down).

[PSALM19.1]

So I guess if you had a laser collimator, after using it I could do a star test to confirm it was ok?

[Asterix2020]

The star test is the ultimate test. But I find it hard to know what to adjust if it indicates a problem.

[daik]

I have the orion laser collimator, and I've used it a number of times on my dob. I find it is actually quite good. Mind you my dob has a quite dirty and damaged mirror so if the collimator is a little off I would not discover it. Given the price of it I think it is a good buy.