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mejacobs
member
Reged: 07/25/09
Posts: 43
Loc: Minnesota
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Hi. I'm a relative newcomer here. A few months ago I bought my first telescope. I have it mounted on with a Universal Astronomics Macrostar Deluxe. So far I have been very pleased with the performance, but I have one question that perhaps others who have used alt-az set-ups could answer: When using the scope, especially at higher powers, how much should the alt. and az. axes be tightened? There is some jerkiness (backlash?) when I nudge the scope at higher powers. Is that a sign it's tightened too much? I guess I'm just not certain how much the scope should be kept steady largely by proper balance verses by tightening the axes? Any advice on this front would be greatly appreciated.
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Intes MK-67 6" f/12 Mak-Cass
UA Macrostar Deluxe Alt-Az on Surveyor Tripod
EPs: Agena 38mm SWA, Meade 20mm QX, Zhumell 12.5mm Z Series Planetary, Burgess/TMB 9mm Planetary
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coopman
Carpal Tunnel
Reged: 04/23/06
Posts: 1544
Loc: South Louisiana
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You should try to balance the OTA as well as possible on the mount. I've got a Unistar Light and a Unistar Basic, and I don't recall having any backlash issues with them. If you've got the balance right, I would not think that you should have any backlash, but I'm not familiar with your particular mount. You can call Larry at Universal Astronomics and discuss it with him.
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Regards,
Clay
"The heavens declare the glory of God; the skies proclaim the work of his hands." Psalms 19:1
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sailor70623
scholastic sledgehammer
Reged: 01/12/08
Posts: 944
Loc: Ok.
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The axes (clutches) should be tight enough that the scope doesn't slip while slewing. They could bind if tightened too much. Having the scope balanced will allow it to slew with out having to tighten the clutches too much. Unless you are over loading the mount. But I doubt that.
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Corornado PST
LB 16" & 12"
Z 10"
LX50 8"
8" CPC
ETX127
102&90mm MAKs
80mm Richfield APO
70mm refractor
ETX60
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Tony Flanders
Post Laureate
Reged: 05/18/06
Posts: 3469
Loc: Cambridge, MA, USA
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Quote:
When using the scope, especially at higher powers, how much should the alt. and az. axes be tightened? There is some jerkiness (backlash?) when I nudge the scope at higher powers. Is that a sign it's tightened too much? I guess I'm just not certain how much the scope should be kept steady largely by proper balance verses by tightening the axes?
With any friction-based mount, you basically want as little friction as you can get away with. If the scope is set up on level ground, there's usually no reason to tighten the azimuth axis very much at all, because there's no force pulling it in that direction.
The altitude axis is a judgment call. If you keep it completely loose, then you may have to tweak the balance every time you change an eyepiece, which is more hassle than I'm willing to put up with. But you certainly don't want it tighter than you need.
I'd say the ideal is to balance the scope perfectly for your average eyepiece, then tighten the altitude axis just enough to keep the scope from slipping when it's pointed horizontally and you're in the process of changing EPs, with no eyepiece in the focuser. That's when the scope is maximally front-heavy.
Incidentally, Larry Patriarca is more than happy to help with any problems relating to his mounts.
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Tony Flanders
First and foremost observing love: naked eye.
Second, binoculars.
Last but not least, telescopes.
And I sometimes dabble with cameras.
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tigerroach
sage
Reged: 08/13/08
Posts: 465
Loc: Houston, TX
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With my 4", I balance my mount for the shorter eyepieces, so I can have very smooth movements with little friction when following planets etc. at higher powers. When I whip out the 35mm panoptic for some low-power work on DSOs I have to tighten the altitude bearings a little, but it isn't much of an inconvenience to have some friction at lower power.
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Brian
TeleVue TV-102, Gibralter alt-az mount
Webster 14.5" f/4.3 truss dob *under construction*
Canon 10x30 & 15x50 IS binocs
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mejacobs
member
Reged: 07/25/09
Posts: 43
Loc: Minnesota
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Thanks for the input. I'm probably relying too much on friction and not enough on balance.
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Intes MK-67 6" f/12 Mak-Cass
UA Macrostar Deluxe Alt-Az on Surveyor Tripod
EPs: Agena 38mm SWA, Meade 20mm QX, Zhumell 12.5mm Z Series Planetary, Burgess/TMB 9mm Planetary
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KerryR
Pooh-Bah
Reged: 12/05/07
Posts: 1172
Loc: SW Michigan
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Keep in mind, too, that these mounts need a little break in time for the Teflon disks to 'wear in'. Things'll get smoother over time. Definitely, balance well.
It's sometimes usefull to tighten the central bolt of alt-az scopes that don't use a counter balance weight (or second scope). If the center bolt (of either axis) isn't tight enough, the weight of the scope pulls the one bearing plate too far out of paralell with the other bearing plate, which puts a lot of the weight of the scope on just the outer edge of one side of the bearing suface. The result is a high degree of stick-slip. Too tight, though, and things'll get too sticky. It's OK for the movement to be a little stiff, but you don't want them to stick and then suddently slip (causing over-shoot), or flex other parts of the system before they slip. It can be stiff, but "buttery smooth".
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Kerry
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