Setting up a Vixen GP mount - couple of questions

[davidrandell]

Hi everybody,

I am commissioning an old (green livery) Vixen GP mount that I have and have a few questions about setting this up. So any help would be welcome, thanks.  The first question is about the Vixen polar-finder's reticle. This had become loose and needed to be re-seated after initially trying to adjust and align it with the rotational axis of the mount. Is there a default orientation of this reticle wrt the polar finder housing or does it not matter? The other question is about the (black) RA and Hour ring and (siver-grey) date ring. Both of these appear to be locked together and the only way I can rectify this is to partly unscrew the polar scope form the mount, then turn the one dial relative to the other before re-inserting the polar scope. But when re-inserted and gently tightened up I cannot turn the silver-grey Date ring independently wrt to the RA and Hour ring. This does does not seem right to me; is it?  Thanks.

David R

[BinocularSky]

33 minutes ago, davidrandell said:

I am commissioning an old (green livery) Vixen GP mount that I have and have a few questions about setting this up. So any help would be welcome, thanks.  The first question is about the Vixen polar-finder's reticle. This had become loose and needed to be re-seated after initially trying to adjust and align it with the rotational axis of the mount. Is there a default orientation of this reticle wrt the polar finder housing or does it not matter? The other question is about the (black) RA and Hour ring and (siver-grey) date ring. Both of these appear to be locked together and the only way I can rectify this is to partly unscrew the polar scope form the mount, then turn the one dial relative to the other before re-inserting the polar scope. But when re-inserted and gently tightened up I cannot turn the silver-grey Date ring independently wrt to the RA and Hour ring. This does does not seem right to me; is it?  Thanks.

David R

Hi David, it's been a very long time...

Your reticle question is probably best answered with images; you can download a GP manual as a PDF from http://psygr.belxm.servertrust.com/v/vspfiles/images/GPMounts.pdf or, if you prefer it without watermarks, as individual image files from http://arnholm.org/astro/gpmanual/

The hour ring is fixed unless you slacken the locking screw above it - you would normally lock it to 0h for polar aligning and slacken it for observing, if you were using it as a setting circle. When you rotate the polar axis, the date ring should rotate with it (i.e. it should be locked to the polar axis.)

Is that any use?

[davidrandell]

1 hour ago, BinocularSky said:

Hi David, it's been a very long time...
Your reticle question is probably best answered with images; you can download a GP manual as a PDF from http://psygr.belxm.servertrust.com/v/vspfiles/images/GPMounts.pdf or, if you prefer it without watermarks, as individual image files from http://arnholm.org/astro/gpmanual/

The hour ring is fixed unless you slacken the locking screw above it - you would normally lock it to 0h for polar aligning and slacken it for observing, if you were using it as a setting circle. When you rotate the polar axis, the date ring should rotate with it (i.e. it should be locked to the polar axis.)

Is that any use?

Well well... Yes it has been a very long time! Happy New Year to you! 

Yes your post was useful thanks.

The issue with the reticle was not recentering it, it was the fact it can be positioned throughout the 360-degree range wrt the polar scope housing. I just wondered if there was a default orientation that Vixen tend to adopt, because  if not, when the polar scope is screwed into the mount that reticle can then appear to be in any arbitrary orientation.

Dave

 

 

[BinocularSky]

5 hours ago, davidrandell said:

 

I just wondered if there was a default orientation that Vixen tend to adopt, because  if not, when the polar scope is screwed into the mount that reticle can then appear to be in any arbitrary orientation.

Covered at the top of p8 of the pdf manual.

[pete_gamby]

If I read this correctly, you want to know how to check the alignment of the reticule within the scope, not the alignment of the scope with the mount?

If that's the case then these are the instructions we have had from Vixen:

1) Look at a distant building or a four-sided figure through the polar scope and fit the straight-line reticle in the field of view of the polar scope to a perpendicular line of the building by turning the polar scope.  Do not turn the setting circles simultaneously.  Turn only the polar scope tube part by pinching the eyepiece barrel with fingers.

2) Set the time setting circle so that the "0 hour" on the time setting circle goes to the top by watching the bubble level.

3) Turn the date setting circle so that the "01h20m" on the date setting circle matches the "10th October" on the date setting circle.

4) Loosen the set screw on the time meridian indicator ring and turn the ring so that the white line matches the "0" on the meridian offset scale.  Then, tighten the set screw.

Hope that makes sense!

Cheers, Pete

[davidrandell]

On 09/01/2017 at 10:01, pete_gamby said:

If I read this correctly, you want to know how to check the alignment of the reticule within the scope, not the alignment of the scope with the mount?

If that's the case then these are the instructions we have had from Vixen:

1) Look at a distant building or a four-sided figure through the polar scope and fit the straight-line reticle in the field of view of the polar scope to a perpendicular line of the building by turning the polar scope.  Do not turn the setting circles simultaneously.  Turn only the polar scope tube part by pinching the eyepiece barrel with fingers.

2) Set the time setting circle so that the "0 hour" on the time setting circle goes to the top by watching the bubble level.

3) Turn the date setting circle so that the "01h20m" on the date setting circle matches the "10th October" on the date setting circle.

4) Loosen the set screw on the time meridian indicator ring and turn the ring so that the white line matches the "0" on the meridian offset scale.  Then, tighten the set screw.

Hope that makes sense!

Cheers, Pete

Hi Pete,

Thanks for your detailed reply, much appreciated -  but  that was not the source of the problem. The problem turned out to be  mechanical one. Basically when I locked the RA ring at "0" using the small RA ring set screw on the top of the casing and rotated the head in RA the Date ring did not turn. So it was impossible to set the correct orientation of the reticle for a given date and time to do the polar alignment. What had happened was that the three grub screws used to secure the RA ring nut lock has loosened meaning that when you turned the head in RA the Date ring was not turning as it should. I removed the polar scope assembly and RA ring and RA set screw then was able to access the three grub screws to tighten these up. Its fine now.

Dave