Vixen GPDX Polar scope

[Hal 9000 (Phil)]

Does anyone know how to rotate the reticle inside a vixen gpdx polar scope as I would like to try to set polar alignment. I can see the 3 grub screws which i asume is for the initial alignment to the mount.

Hal 9000

[The Mekon (John Briggs)]

Phil,
you do not rotate the polar scope. You rotate the whole RA axis. Can be done with the scope on or off, but as the scope sometimes ends up upside down, best done with it off. Really not necessary though as you can estimate the position of the SCP by looking at where sigma octans is in the field. You easily can get to within 15' of the SCP this way, which is good for visual and short focal length astrophotography. To get a better alignment you may need to drift align, even if the pattern is properly aligned.

[Dennis]

Hi Phil

Generally, out-of-the-box, there should be no need to rotate the illuminated polar alignment scope (PAS) reticule, at least that was my experience on my previous GP and GP-DX mounts.

From memory, all I used to do was roughly align the mount using a protractor (to set the rough altitude) and compass (to set the rough azimuth). This usually placed the 4 stars of the Octans “trapezium” in the field of view of the PAS. I then released the RA clutch to rotate the RA axis so the reticule roughly aligned with the Octans stars and then clamped the RA clutch and fine tuned the polar alignment using the mount altitude and azimuth fine adjustment knobs on the mount.

Cheers

Dennis

[marki]

Don't undo the grubscrews as you will knock the polar scope out of alignment and have to reset it to get anywhere near polar alignment. As suggested below just leave the scope off and rotate the RA axis or better still use alignmaster.


Mark

[Dennis]

If you have adjusted the 3 grub screws or think that the RA axis and the optical axis of the PAS are misaligned, all is not lost. You can align these axes quite easily in the daytime.

See the attached screen print from the Vixen manual.

Cheers

Dennis

[Hal 9000 (Phil)]

I believe the reticle has moved or been moved as I am unable to set the correct position as shown by the 4 octan stars. Does the recticle have to be in a starting position prior to starting a new polar scope to mount alignment or can that be rotated to any position. Once the polar scope is aligned do I then rotate the RA head until I get the polar stars close and use the ajustnebt bolts to center.

Phil

[marki]

1. Put octans in the FOV
2. Rotate the RA so the 4 stars are roughly aligned with the outline on the polarscope.
3. Use the ALT/AZ adjusters to put the 4 stars in the circles.

If you polar scope is properly aligned you are done bar drift alignment if you want to go the whole hog. All the indexed dials are for the Northern Hemisphere and don't work down here so it doesn't matter where they are. Still think alignmaster is more accurate and a whole lot quicker e.g. 3 iterations and you are taking good clean subs with autoguiding (takes about 5 mins).


Mark