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All of the optical polar alignment scopes, like the Losmandy one, or the Orion Atlas one, have a small diameter fragile, round glass plate, having the markings etched on (photo lithographed out of a Chrome metal layer, like used in the semiconductor industry for litho mask layers).

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That small glass disk is held in place in the polar scope by 3 very tiny setscrews at 120 degree separation around the perimeter circle.??

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The setscrews must not be screwed in tight on the glass, because the glass will chip, or worse, will crack.??

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If one setscrew is very loose, the glass disk will move, just as you report.? So I think this is the cause of what you are seeing.? As the mount revolves in RA, gravity is shifting the glass "reticule" plate around until it falls on to the bottommost 2 setscrews.

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Your job when setting up your polar scope is to very carefully:

1. Remove your scope and counterweights and counterweight shaft.

2.? Shift your DEC axis shaft til the scope porthole is fully open.?

3. Point your RA at a distant landmark point. I use a faraway treetop tip.??

4. Carefully tighten in a setscrew til the glass plate does not shift was you rotate the polar scope around in a circle.? Not too snug! Don't want to crack the reticule glass!

5. Look at the center cross or marker on the reticule. You want that center mark to remain

? ? a. Centered in the rotating reticule

? ? b. Move the AZ and Elevation to get that center for on the distant landmark point.?

6. To do that, you will have to:

? ? a. Loosen one setscrew

? ? b. Tighten one or both of the remaining setscrews.

7. Once you are done, the reticule is centered in the rotating RA axis shaft.? Leave the polar scope in place and/or mark it's orientation on the RA shaft. If you rotate that polar scope location, you will likely lose the centering of the reticule (because the machined RA axis is not perfect optically).

8. Now move your mount back to approximate polar alignment.??

9. Use a simulation of the Polar Scope View to know where Polaris should be seen through the polar scope. (The EQMOD software has a polar scope simulator for this.? Generally, Polaris is 180 degrees reverse from the sky she you'd see with Stellarium or other sky chart.)

10. Use the drift alignment method to perfect the RA alignment before deep sky imaging.??

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(You might want to download and read the description of the polar scope adjustments in an Orion Atlas mount manual.)

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Hope this helps,

Michael

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On Fri, Jan 10, 2020, 1:33 PM Nels Johansen via Groups.Io <nhbj6=[email protected]> wrote: