fine azimuth adjustments for polar alignment
Posted 21 November 2012 - 08:36 AM
does anyone have hints on how to do really fine polar azimuth adjustment?
i think the typical azimuth bolts are 1/4" - 20tpi or similar. If the polar base is 5" in diameter, one turn of the azimuth bolt would be 1.15 degrees, so the typical 1/4 turn would be about 0.3 degrees or 18 arc-minutes.
Given that, how can one get a really close alignment to the pole?
secondly, often the mount base binds, so when you turn the azimuth bolt, the base doesn't rotate. when you turn it some more, it then rotates (by a large amount).
so these two issues make a really good polar alignment difficult.
any ideas? is there some material one can put between the mount and its base to lessen friction and make azimuth adjustments smoother?
Posted 21 November 2012 - 09:24 AM
Posted 21 November 2012 - 09:25 AM
Posted 21 November 2012 - 02:20 PM
Is there some material one can put between the mount and its base to lessen friction and make azimuth adjustments smoother?
Here you go: UHMW sticky-backed material. A friend and I tried this stuff and it made a *world* of difference. It's almost as if the AZ was on roller bearings - it made that much difference. And that's with the mount tightened down hard before making the AZ adjustments.
Posted 21 November 2012 - 10:52 PM
is there some material one can put between the mount and its base to lessen friction and make azimuth adjustments smoother?
I used a bar of soap and rubbed it on the tripod head where the mount base sits. Now with the mount tightened as much as I can, adjusting the azimuth is almost too smooth! Works great, cheap, clean, doesn't attract dust and when it wears off, do it again.
Posted 21 November 2012 - 11:01 PM
Posted 21 November 2012 - 11:52 PM
The UHMW is probably the posh solution, styrene is the low-end one and the soap is the lowest.
Will try the soap first. :-)
Posted 22 November 2012 - 11:33 AM
Posted 22 November 2012 - 11:53 AM
Removing any loose paint, smoothing the upper surface (lower too but that can be quite tough to do), and adding plastic/synthetic "bearing" or a little lubricant all help the situation, sometimes dramatically. But you need to be careful about adding anything in between ... it should be as thin and strong as possible or you may experience some tilt before the center bolt is fully snugged down.
On heavier mounts like the CGE and CGEPro there is a different setup to attach the electronics pier to the base of the mount. It has much more surface area and usually only requires a very thin film of suitable lubricant (grease) to maintain the ability to move in azimuth without binding or tilting. On the original CGE the cam style Az adjustment bolt doesn't offer a very fine movement capability, but there is a 3rd party solution that adds a fine screw type of adjustment (from TPI Astro).
Posted 22 November 2012 - 12:47 PM
i figure before blowing a huge (for me) wad of cash on a Mach1 or Tak to fix my declination guiding issues, i should just try to get a perfect polar alignment so i don't need to guide in declination.
this has proved troublesome because of the rough azimuth adjustment.....