Thanks Greg.... that agrees with what I remember. My 18" Obsession shows that "drift" on the
primary too. Good call, and nice suggestion about collimating at 45 degrees.
Greg LaFlamme wrote:
> My 15" f5 also has laser drift when moved from horizontal to vertical but
> in my case it has nothing to do with movement of the primary, its the
> "supply beam" from the secondary TO the primary that shows the error first.
> The red dot will drift horizontally from left to right when the scope is
> moved 90 degrees in altitude about a 1/8" center to center. I believe this
> is caused by slight amount of shear flex in the ota itself (on the long
> axis) but I'm not certain, its a tricky bug to work out and a bunch of
> scopes have this issue. To "cure" it, I collimate the scope while its at
> about 45, this way I split the difference. There is no noticeable difference
> in resolution in my f/5 but maybe it may be noticeable at f/4.5? Not sure...
> I use a 2" Kendrick collimator with a barlowed angled face so I can stay
> back at the primary when collimating it. Every so often I check mechanical
> alignment with a Cheshire.
>
> GML
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Received on Thu Mar 13 18:39:39 2008