Re: Laser versus Non-Laser Collimation

From: Larry G (no.one_at_nowhere.com)
Date: 03/02/05 

Date: Tue, 01 Mar 2005 19:45:09 -0600

On 28 Feb 2005 19:33:17 -0800, canopus56 <canopus56@yahoo.com> wrote:

> Larry G wrote:
>> Contrary to widespread myth, it is not necessary to "offset" the
> secondary
>> for proper collimation.
>
> Larry, your drawing, when compared with Olof Carlin's, nicely
> illustrates the key difference of offset and not-offset collimation.
>
> In your collimation eyepiece barrel drawing at -
>
> http://www.vvm.com/~piscescs/collimat/images/Diagonal_Offset_2.gif in
> http://www.vvm.com/~piscescs/collimat/NoTools2.html
>
> the reflection of the secondary mirror is more or less centered and the
> secondary mirror is not centered, toward the primary. This is
> "non-offset" collimation.

Actually, the image shows a slight offset, though perhaps not noticeably
so at first glance. For most newtonians, offset is a matter of a tenth of
an inch or so, for scopes in the 6 - 10" range. Repointing the primary
to intersect the diagonal a bit more toward the focuser is a much easier
adjustment to make, than to actually reposition the diagonal.

Cheers,
Larry G.

Relevant Pages

  • 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: Collimination Non Problem (I hope)
    ... I had the same concerns about the collimation of my 8". ... but the reflection from the inside of the ... my drawing, the offset was to the left in the picture), and they said ... They said the offset ...
    (sci.astro.amateur)
  • 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)
Quantcast