Re: Collimation Question

Jeff,

If the cap (which is some kind of sight tube) and the laser do not agree,
the problem is often, that the diagonal is slightly tilted to one side (to
the left or to the right or rotated to one side. If this is the case, your
secondary can look centered in the cap, but the laser will not fall on the
optical center. When you then adjust the secondary to make the laserspot
fall at the center, the secondary doesn't look centered any more in the cap.

--
Jan
http://members.ziggo.nl/jhm.vangastel/Astronomy/
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"Jeff Turkstra" <turkstra@xxxxxxxxxx> schreef in bericht
news:gg08ih$glc$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
For the past few years I've used the laser collimator (an Orion
"LaserMate Deluxe") that came with my Dobsonian to align the optics. In
a quest for better collimation, I resorted to the collimation cap that
also came with the telescope. (It's basically a piece of plastic with a
tiny hole in the center).

The problem is when I use the collimation cap, the laser ends up about
an inch off the center of the primary. If I use the laser, the view
through the collimation cap isn't what it should be. In particular, the
reflection of the primary is off to the left.

I've spent some time reading a few sites on the web, and I've concluded
that what I really need is a good Cheshire and sight tube. This,
however, costs money.

Assuming that my only two options are the collimation cap and the laser,
which one would you choose?

My suspicion is that the laser itself isn't collimated, but when I place
it in a stationary V, point it at a wall, and rotate it, the point
appears to stay in a fixed location on the wall. So maybe it is.

I guess the real test will be the next time I get a clear night.

Anyway, I was curious if anyone else had an opinion on the matter. Thanks!

- Jeff


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