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on 8/13/04 9:43 AM, Robert Gainer at robert_gainer_2@HOTMAIL.COM wrote:

> Frank,
> I have thought about what you said and still don?t under stand it. So I set
> up this morning and preformed this little test. Please explain to me where I
> went wrong in my design for the test. First I want to describe the setup for
> this experiment. I arranged this so that I could take the shot though the
> open door of my office. The sextant used was my Cassens & Plath. I believe
> this instrument to be accurate. I set a stand on a tool cart and locked the
> sextant into it. Then I measured the angle between the top of the spire and
> the edge of the roof on a building that is about 7,000 feet away. This
> distance was measured from the town-zoning map. All the measurements were
> done with my 4-power scope. With the sextant still locked in position I
> released the scope and shimmed the bottom of the post with a 1/16? thick
> spacer. This put a noticeable misalignment in the scope. I also did this a
> second time with the spacer at the top of the post and saw no difference in
> the measured angle either way. Next I put the sextant at a 45-degree angle
> and set the index arm so that the roof was an unbroken line on the horizon
> glass. I repeated the use of shims to misalign the scope both up and down
> relative to the frame. I still see an unbroken line on the horizon glass.
> Unfortunately its overcast and I can?t see any other target that is further
> away. I am sure the effect of a misalignment increases as the angle does,
> but I expected at least a small jog in the image.
> All the best,
> Robert Gainer
>
>
>

>Robert,

Unless I missed a message, it looks to me like no one replied to your
posting.  As I read it, it seems your shimming (bottom or top of post) only
serves to tilt the scope upwards or downwards - not left or right so as to
be unparallel to the frame, which is what this is all about.
Ken Gebhart

   

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