9 replies to this topic

[39cross]

I recently acquired a Vixen Custom-D mount as I was looking for an easy to use alt-az mount.  It seems pretty well made and easy to use in azimuth mode, but altitude mode has me sort of puzzled.  I can't find a manual on the web that might explain how to adjust this, so I'm hoping the kind folks here can help me.

 

There is a limited amount of adjustment for the AZ axis using the worm gear. My plan was to set the worm gear at the bottom of the range, and then tighten the axis bolts at an angle high enough to cover the likeliest lowest part of the sky I'd look at, and hope the slo-mo control would give me enough travel to go up as high up as I'd wish for.  To my surprise, after mounting a 100cm refractor, I was able to tilt the scope up and down without using the control.  But not too surprisingly, at a high enough angle the scope would start to slide downwards.

 

I was able to loosen the outer acorn nut, which I assume is there to keep the inner nut from slipping outward.  I tightened up the inner nut to the point where the mount will not move up/down unless the slo-mo control is used.  However - I'm not really sure what the intent of Vixen was.  Should the nut tension allow the scope to be pushed up and down? In which case, it seems you run the risk of having it slip.  Or should it be moved up and down only using the worm gear?

 

Thanks,

Rick

[Terra Nova]

I had Vixen Custom-D mount about twenty or so years ago and liked it a lot at the time. I had built up a lot of experience over the years using the Mayflower model 814 mount and a Unitron 114 mount, and like the Custom-D, neither one of those had 360° gearing on either axis but instead, had to be reset every 20 to 30 degrees of arc. My pattern was to note the direction I was looking and how the stars were moving (rising or setting) and then set the tangent gear low (or high) accordingly.

 

As far as locking that acorn nut on the altitude axis, isn’t there a friction bearing in there? I thought I remembered one. If not, maybe add one cut from gasket fabric?

Edited by Terra Nova, 16 July 2023 - 11:00 AM.

[39cross]

Thanks Terra!  Did you carry a wrench with you to loosen the nuts and readjust the azimuth?  Or did you adjust the gearing as appropriate, and then move the scope up or down by hand?  There is a washer on the inside of the two nuts, is this the friction bearing?  I think I can probably adjust the tension so I can manually move the scope tube up and down without it sliding on me, but I'd like to confirm that's how it's supposed to work.

[jkmccarthy]

39cross --

 

Not too long ago there was a discussion thread here -- https://www.cloudyni...ment-wont-hold/ -- regarding optimum tuning of the friction in the altitude axis of a Vixen Custom alt/az mount, that might be helpful ?   I realize your mount is the Custom-D (deluxe?) version, with the counterweight to offset the weight of the OTA around the altitude axis, and thus allow for heavier OTAs.   But echo'ing what Terra Nova stated above, my understanding is that the optimum adjustment of the altitude axis' acorn-nut and jam-nut is where there is more than enough friction to hold the OTA at any chosen altitude (and allow fine-adjustment using the slow motion flex-cable), but not so much friction that it becomes difficult to change the altitude pointing manually by pushing-down / pulling-up on the eyepiece end of the OTA (i.e., without fear of bending the tube in the process!).   By finding the "sweet spot" between too little friction and too much friction on the altitude axis, and then holding stationary with one wrench the inner nut (closest to the mounting) so that ideal friction adjustment is maintained while you tighten with a second wrench the outer (acorn) nut *hard* against the inner nut, you should be able to use the Custom alt/az mount at night without needing to have wrenches on-hand to loosen and re-tighten the altitude nuts as you change OTA position in the sky by manually moving the telescope from the eyepiece end, without having to 'slew' the telescope in altitude using the slo-motion tangent arm mechanism.

 

Perhaps marcyc can add to this thread her first-hand experience with her Custom-D -mounted Vixen 100M ?   What size OTA do you have mounted atop your Custom-D alt/az ?   Is the supplied counterweight close to being the right weight to balance the OTA on the mount at high altitudes ?

 

Hope this helps,

 

        -- Jim

[39cross]

Thanks Jim, that explains all I need to know to make the adjustments. In my research on the Custom-D I never came across that thread, thanks so much for the link.  I'll readjust the mount accordingly and see if it holds.  I am trying it with a 100mm refractor (f/7.7).   I don't think I need to use the counterweight, but I haven't gotten there yet.

[39cross]

Finally had a sorta clear sky last night so I had a chance to try the mount - post-adjustments - on the moon and it worked very well. I have a Vixen ED103S mounted on it, no counterweight required.  It makes for a nice light grab-n-go combo.  Tonight promises to be better so I'll give it more of a workout.  However it seems very promising now.

 

Terra and Jim, thanks again for your replies!  Perhaps in the future someone will stumble on this thread and it will help them out.

[Terra Nova]

Thanks Terra!  Did you carry a wrench with you to loosen the nuts and readjust the azimuth?  Or did you adjust the gearing as appropriate, and then move the scope up or down by hand?  There is a washer on the inside of the two nuts, is this the friction bearing?  I think I can probably adjust the tension so I can manually move the scope tube up and down without it sliding on me, but I'd like to confirm that's how it's supposed to work.

Never carried a wrench, just reset/adjusted the gearing on either axis whenever either one ran out of thread.

[Nightflight]

Hello folks, I saw a reference to this old thread in another post. Just one more datapoint re. adjustment of a Vixen Custom alt/az mount:  I also follow Jim McCarthy’s excellent instructions above to get to the proper tension set point.  I recently disassembled the alt pivot assembly on my Custom mount and cleaned out the old grease, including a wipe down of the two nylon washers on either side of the alt pivot. I regreased with Tribology Tech-Lube T-777-2 BG, reassembled, lightly oiled the through bolt, then threaded on the jam nut and tightened it until the scope moved smoothly and did not  slip/fall backwards or forwards anywhere in the alt arc. Once I got to that point, I then held the jam nut in that same position with a thin wrench, and tightened/ torqued the acorn nut to 45 ft/lbs.  The mount works beautifully with my Vixen 80M, and I have never needed to add any extra lock washers or other hardware to it.  Cheers!

[deSitter]

Hello folks, I saw a reference to this old thread in another post. Just one more datapoint re. adjustment of a Vixen Custom alt/az mount:  I also follow Jim McCarthy’s excellent instructions above to get to the proper tension set point.  I recently disassembled the alt pivot assembly on my Custom mount and cleaned out the old grease, including a wipe down of the two nylon washers on either side of the alt pivot. I regreased with Tribology Tech-Lube T-777-2 BG, reassembled, lightly oiled the through bolt, then threaded on the jam nut and tightened it until the scope moved smoothly and did not  slip/fall backwards or forwards anywhere in the alt arc. Once I got to that point, I then held the jam nut in that same position with a thin wrench, and tightened/ torqued the acorn nut to 45 ft/lbs.  The mount works beautifully with my Vixen 80M, and I have never needed to add any extra lock washers or other hardware to it.  Cheers!

I just got this mount in a SGW find and I immediately ditched the two nuts. They will be replaced by a big M12x1.75 through-hole clamping knob - no grease on the washers or axle at all. The idea of relying on the stock configuration was just not something I would ever get used to. Here's the knob, for anyone wanting to try it.

 

https://www.amazon.com/dp/B0CLQP55QM

 

-drl

Edited by deSitter, Yesterday, 11:24 AM.

[grif 678]

Just make sure that before you do all the adjusting, that the OTA is in the right place in the tube rings. When I had mine, I would move the scope to being close to the altitude that I would be viewing. Leaving it at  that altitude, I would move the OTA back or forth in the tube rings so that it balanced without tightening the altitude tension. That way there is hardly any pressure on the altitude adjustment when using, making it turn easier with your slow motion cable. Just a tip to ave on the wear and tear of your mount. If you have the OTA either to far back or forward, it puts added pressure on the tension screw when you move it against the weight of the tube.

Billy