Collimation Craziness

Well I've dove into the world of reflectors recently. My newest toy is an orion 6lt ota on a starfinder eq mount. Its a 6" f/8 reflector which i know means you don't have to be exactly perfect on its collimation but I like to be as precise as I can. Heres my problem, I've collimated it 3 times using just the provided hole in the eyepiece cover deal and I get it all perfectly lined up like all the diagrams I see on the internet. But then I stick in my laser collimator and the dot hitting the primary is a inch right of the donut and the return beam barely hits the diagnol on its way back. Now if I do the laser collimator way first and align the beam using the secondary collimation screws to the donut on the primary than use the primary collimation screws to make the return beam come back into the hole of the collimator. I take it out and put the collimation cap back in and it doesn't even look close, the circles don't match up and I can only see 3/4 of the main mirror!! I havn't had time to test it under the stars (rain forcasted for the next week I was just wondering if anybody had any idea what the problem could be or what I might need to try and do to make them match! THANKS A LOT!!

Thomas Shmalberg (reflector/collimation newbie),

"Keep Looking Up"

I'm pretty new myself. Here is what I would consider:

1. Is the laser collimator properly aligned. I have a howie glatter model and its pretty rugged. Some models are more misalignment proof than others.

2. I always align the secondary to hit inside the donut on the primary first, then align the primary. I may go through this step 2 or 3 times before both the secondary and primary appear aligned.

3. If you are using a rack and pinion focuser, there may be some play in the focuser. The further I focus out (run the tube out) the worse the alignment seems. Use the laser with the focuser tube mostly in close. Also the focuser may have some up and down, left and right play. Can you wiggle the laser collimator around a bit in the focuser?

4. I thought when I bought the laser I would rule the collimation world. Not so. The puny $20 cheshire sighting tube with crosshairs gets it closer, to just a tweak of a turn on a collimation screw. Suprisingly accurate. I'm constantly off more with just the laser alone.

5. Have you checked the angle of the focuser to the OTA. Just a 1/4 inch of 90 degrees can through you off considerably. The focuser alognment should be the first on the ota checked, otherwise, the scope just won't collimate very well. And frustration sets in.

Hope this helps

David Roberts

May I suggest just being patient and waiting for a clear night.... collimate with the laser then test on a star.. If test is good then you will know for sure... Unless you test on a star the rest is just theories and guess work.

Mark V

1. The focuser may not be perfectly square to the tube.

2. The secondary may not be perfectly square to the focuser. (Check this visually, and if you can see anything wrong asume it's just fine for an f/8 system)

3. The laser may be out of adjustment (and with an f/8 system is more likely to cause problems than to fix them.

The first thing I would do is a star test, once you've go the concentric circles the optics are in line with each other. The go back and shim the focuser until things line up better. then check the views and do another star test (which should not have been changed by fiddling with the focuser).