Michelle rightfully said:
You can align with only a laser and be completely off on your
collimation. That is because the laser only works to make sure that
you can reflect the light beam back on itself. It doesn't check for
proper alignment of the optics.
-------------------------------------
I'm going to quote Jamie here: Sing it bruddah!
I rented one of the Johnsonian carbon fiber scopes a few years ago for
a backpacking trip into the Sierras, and
I experienced this. Those scopes had a lot of flexure that could not be
eliminated. I did use a laser to collimate, but I also checked
collimation before I left my house with the mechanical tools from
Tectron. They did not agree.
As a matter of expediency, I took the laser that came with the scope,
and could adjust the secondary and primary onsite to get the center
spot reflection all the way back to the laser in the focuser.
Nonetheless, when looking at Double Cluster, I found I could roll
through focus in the field from top to bottom. It was a real lesson in
how a single reference point that the laser provides does not, in any
way, guarantee collimation across the field.
There are simply too many variables to allow a single reference point
to correct for. Gluing the primary does eliminate one of the potential
variables.
-b.
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Received on Thu Mar 13 20:19:38 2008