Collimation question, over tightened? with pic

First, I am a total newbie- and my pic is a drawing from ms paint.

I have a meade 127ed f/9 with collimation screws. I was getting star patterns that looked like
0)))) when in focus, so after a few hours of figuring out how to adjust it with an artificial star I made out of a pinhole and an LED headlamp at 50 yards, it went away. My views dont have comet tails anymore once the scope cools off. What i have resembles the attached image, which I drew up in about 5 seconds in PAINT. Is this from centering? overtightening? cheapo eyepieces? I get this with my TMB planetary 6mm.

Anyone happen to be in NH and wants to tutor me?

Regards;
Keith Garrett
Wolfeboro NH

Attached Image:

Everything that looks cross-like points towards astigmatism, but you should provide a much better picture for us to be able to say anything. Can you see diffraction rings? If not, your pinhole is too large. Defocus to 2-3 rings and draw them carefully.

Dmitri

Keith:

I've the same issue with a Meade 102ED I recently picked up. What your drawing describes is astigmatism. Note that the red and blue break out at 90 degrees from each other. I bet that the inside and outside of focus star images at high power (150X or more) with 4-5 rings are elliptical and at 90 degrees to each other too. Also if you check with a Cheshire you'll see the "dots" rather widely spaced. Using the collimation screw pairs on the front of the cell to overlay the dots in the Cheshire view yeilds the coma o))))

The ED element needs to be recentered.

What you need to do is collimate with the Cheshire first then carefully remove the three small screws buried on the OD OF THE RIM of the cell close to the collimation screw pairs. Once removed you will have access to another screw in each hole. These are the centering screws. I would back off each of those by say an 1/8 turn. Then, watching the coma image, gently adjust the screws to remove the coma then re-insert the outer screws and gently tighten them to the recentering screws. This locks the inner screws into position.

I dug up the instructions on the yahoo group but have not yet tried it with mine. Looks fairly straight forward.

Good luck

Jeff

I have a meade 127ed f/9 with collimation screws. I was getting star patterns that looked like
0)))) when in focus, so after a few hours of figuring out how to adjust it with an artificial star I made out of a pinhole and an LED headlamp at 50 yards, it went away. My views dont have comet tails anymore once the scope cools off. What i have resembles the attached image, which I drew up in about 5 seconds in PAINT. Is this from centering? overtightening? cheapo eyepieces? I get this with my TMB planetary 6mm.

Was the scope completely cooled down when you did the test?
Were the outdoor temperatures stable or dropping? It might be
possible to make a pattern like this with stratified air in
a horizontal tube (together with the normal refractor issues).
Even if the scope is outside for a long time, there can be issues
if the outdoor temperature is dropping more than 1 or 2 degrees/hour.

You can test for problems in the eyepiece simply by rotating
it. Assuming the star is in the middle of the field, most problems
eyepiece problems of this type will rotate with the eyepiece.