Re: collimating with a Cheshire

This is my favorite site, complete with very clear pictures as to what you
should see in your Cheshire.

http://www.fpi-protostar.com/bgreer/collim.htm

I don't think this link provides good instructions for collimating, and in
fact is isn't meant to do so. From the site:

"This web page is not intended to be a comprehensive overview on how to
collimate telescopes. It was created to only look at one smaller issue; what
should a properly collimated telescope look like when diagonal offset is
incorporated. If you are searching for a more complete step-by-step site,
see Mel Bartel's or Nils Olof Carlin's comprehensive collimation pages.
Also, Andy's Shot Glass has a well-illustrated guide, though it might take a
few minutes to download"

and:

"I have received a few e-mails from telescope owners stating that it is not
important to offset the secondary mirror in Newtonian telescopes. I
completely agree! I re-read this 1997 webpage, and I can see where one could
interpret this as an encouragement to implement offset. That was not my
intention. I only wanted to confirm to myself what the view down into the
optics would look like if the secondary was offset."

Forget the offset of the secondary! The cheshire will work, but you need to
mess around with it to figure out which reflection is which. I think the
laser is more intuitive, but either will work. You seem to be hung up on
collimation, and it shouldn't be this hard. Center the secondary in the
tube, and under the focuser. Rotate the secondary until it looks round. Tilt
the secondary until it points directly at the center of the primary. Tilt
the primary until the reflection of your eye/crosshairs/laser returns to its
source. Close is good enough - by the time you can tell that your
collimation could/should be better you will have gotten better at it. If you
are anywhere near collimated and your views are very disappointing then
collimation isn't your problem.

Dennis


.

Relevant Pages

  • Re: Laser versus Non-Laser Collimation
    ... > offset v. nonoffset collimation: ... > "In other words, if you do not offset, the only implication is that the ... > primary mirror will not be pointed exactly down the center of the tube ... > for two types of views down the focuser tube when checking out my ...
    (sci.astro.amateur)
  • Re: Laser versus Non-Laser Collimation
    ... Vic Menard's collimation page ... "In other words, if you do not offset, the only implication is that the ... primary mirror will not be pointed exactly down the center of the tube ... for two types of views down the focuser tube when checking out my ...
    (sci.astro.amateur)
  • Re: Laser versus Non-Laser Collimation
    ... > collimation techniques. ... That may be helpful but note that as you said, offset is a one-time ... reflection of the secondary will be centered in the reflection of the ... not only will the optical axis not be parallel ...
    (sci.astro.amateur)
  • Re: Laser versus Non-Laser Collimation
    ... Larry, your drawing, when compared with Olof Carlin's, nicely ... illustrates the key difference of offset and not-offset collimation. ... secondary mirror is not centered, ... This is "offset" collimation. ...
    (sci.astro.amateur)
  • Re: Laser versus Non-Laser Collimation
    ... > Larry, your drawing, when compared with Olof Carlin's, nicely ... > illustrates the key difference of offset and not-offset collimation. ... Actually, the image shows a slight offset, though perhaps not noticeably ...
    (sci.astro.amateur)