Collimation hell with a Meade Lightbridge

I am having trouble collimating my new Meade 12 inch Lightbridge and I can only describe the experience as a kind of hell. It began when I tried to adjust the main mirror on the rear of the optical tube assembly. It was a mistake as I didn't read the instructions and I should have been adjusting the three collimation screws on the secondary insead(not so brilliant thinking). Last evening while testing out a new eyepiece, I tried to use a Meade 1 1/4 inch laser collimator to center the image of the diagonal through the focuser. I centered it and tighten the screws, but every time the procedure is repeated the image of the secondary is still not centeredthrough the focuser. In fact if I replace the laser collimator and try again I find the point of the laser beam needs to be centered on the circle marked on the main mirrors center. No matter hows many times I repeat the process it fails to align.
The next step I loosened all three secondary adjustment screws and tried to start over, but the next thing the secondary turned on axis away from the focuser. Now I really have a mess. Can someone help me? Perhaps someone can supply me with a procedure or direct me to a website. This is collimation hell.

- Stephen

Hi Stephen:

Collimation can be frustrating. Take time to enjoy your scope even if it somewhat out of collimation. And be confident that you will figure it out.

My guess is that your collimator is not collimated itself so that each time you remove it and replace it, you are rotating it and you are adjusting the secondary to account for it's misalignment.

The first thing to do is to check to be sure that your collimator is properly collimated. The easiest way to do this is to place it in the focuser and rotate it 360 degrees and watch to see if the beam stays in one spot or it rotates in a small circle. If rotating the collimator produces a circle then the collimator needs to be collimated/aligned. A second possible problem is that the collimator may be a loose fit in the focuser which also adds to the misalignment.

Unfortunately it seems, at least in my experience, that the collimators made in Asian typically arrive out of collimation and even when collimated by the user, do not stay in collimation. I believe there are websites that discuss how to collimate your collimator, it is probably worth a search.

As far as general collimation help, these are the two sites I like:

Larry Gilstrap's No tools Collimation page:

http://www.piscescs.com/astro/collimat/notools2.html

And Nils Olof Carlin's page:

http://web.telia.com/~u41105032/

Nil's is the inventor of the "barlowed laser technique" that has been a big help to owners of faster Newtonians.

I also suggest looking at Howie Glatter's pages. I have been owned a Howie Glatter collimator now for something close 10 years, he builds the best IMHO and they arrive at your doorstep collimated and the stay collimated. His spec is 15 arc-seconds which is 1mm deviation at 45 feet... IMHO, a top notch collimator is a tool worth owning.

www.collimator.com



Best to you and yours

Jon Isaacs

Stephen, Here's a real good article on how to start and finish the collimation process. It all starts at the top with the secondary ...positioning,turning,tilting....then lastly ends with the primary.
http://www.adur-astronomical.com/collimation/astro%20babys%20collimation%20guide.htm
Good luck, Gerry

Thanks people I appreciate the help. Especially to Jon Isaacs for the advice regarding the laser collimator. Yes, it appears mine is out-of-alignment. I only need to find out how to collimate a Meade laser collimator. Information is almost nonexistant. I notice there appears to be three holes 120 degrees apart in circumference around the body of the collimator tube. Each has hex screw set inside the hole. I take it this is to adjust the laser beam. Someone somewhere must have some information how how to achieve this. In the meantime I will collimate the optics another way.

- Stephen

- Stephen

There is a general misconception that somewhat out-of-calibration laser collimators are useless. That is not true. Even if re-inserting/rotating the collimator yields different results, it can still be used to achieve a “reasonable” collimation as long as the following procedure is followed:

1- Insert the collimator and secure it. It should not be touched along with the focuser throughout the procedure.
2- Adjust the secondary to redirect the laser beam to point to the center of the primary mirror center mark. If there is too much laser glow, you can shine light down the tube to reduce the laser glare.
3- Adjust the primary mirror to redirect the return laser beam to the source

Nothing new about the first 3 steps

4- DO NOT re-evaluate collimation if you touch the laser collimator or the focuser. DO NOT re-evaluate collimation if re-inserting/rotating the laser collimator moves the laser beam away from the primary center.

A slightly miss-calibrated laser collimator does an OK job with the primary mirror axial alignment which is critical to minimize “coma”. It does a poor job in aligning the focuser axial alignment which is not as critical for visual observation.

Of course, as others suggested, using barlowed laser is the recommended method for aligning the primary mirror.

Jason

8) I appreciate all the information that you people on this forum are providing me. So far it seems to be working. I hate to think the $70.00 I spent on the Meade collimation laser was a waste of money, yet all that matters is the telescopes optics are aligned. I have located most problems and are solving them, yet, I have one that is concerning me. It appears one of the top truss lock knobs will not firmly hold the front optical tube assembly on the Lightbridge. I tighten it, but grabbing the scope from the front I can feel it jimmying around. The knobs or the holes in the upper OTA don't appear to be stripped. Is this considered normal? The only thing I can think of that did this is the knobs that come with JMI's transporter kit. I only hope that some metal was not removed. I have been very careful not to cross thread anything.


- Stephen