Re: Balance Procedure


Joe Zeglinski
 

Thanks Jeff,

I had forgotten about the large initial worm stress, with no OTA. I
suppose if it can (and must) survive that, then the normal imbalance is no
issue at all, in comparison. I had some concerns about operating the mount,
and not rebalancing on meridian changes, if something of the size of say a
large SBIG camera were hanging out there. Shifting weights so often, to
protect the worm drive, would be a hassle. I'm also relieved, that the servo
motors have a safety trip point protection circuit against this as well.

I see from your comparison of the 600GTO and 1200GTO mounts, that I made a
very good decision in purchasing the AP900, in this regard.

Thanks for the added reassurance. The AP900/1200 are one heck of a nearly
bullet-proof mount.
Joe

----- Original Message -----
From: "Jeff Young" <jey@adobe.com>
To: <ap-gto@yahoogroups.com>
Sent: Wednesday, April 25, 2007 11:10 AM
Subject: RE: [ap-gto] Balance Procedure


Joe --

I accidentally balanced my 600E GTO once without diagonal or eyepiece.
When a 2" diagonal, 2" Barlow and T4 Nagler was added, it produced
intermittent stalls when slewing (but not when tracking). I'd guess it
was about 40 in-lbs out of balance.

I never re-balance my 1200 GTO with equipment changes. I might go from
no eyepieces in either SCT or refractor to a heavy T5 Nagler in each
with a Barlow in one. These weights are much farther out on the moment
arm, so I'd guess we'd be looking at more than 100 in-lbs of inbalance.
I've never had this mount stall.

Lastly, when I load up my scopes on the 1200, I load the c-weights
first. This leaves the mount temporarily some 2,500 in-lbs out of
balance.

Cheers,
-- Jeff




________________________________

From: ap-gto@yahoogroups.com [mailto:ap-gto@yahoogroups.com] On
Behalf Of Joseph Zeglinski
Sent: Wednesday, April 25, 2007 3:22 PM
To: ap-gto@yahoogroups.com
Subject: Re: [ap-gto] Balance Procedure



Hi Roland,

This is good news - I was becoming concerned about
"meticulously"
rebalancing the counterweights, every time I crossed the
meridian. Indeed, the
AP900 is a superb design, and even more so, from what you say
about the
rebalance issue.

One question:
You use the phrase "8 lbs out of balance", do you mean 8
inch-lbs?
Being "out of balance" with an 8 lb camera overhand at 6 inches
is different
from the same weight overhanging 2 feet away. Could you be more
specific about
the "moment arm" on the OTA imbalance you are describing?

Actually, it would be interesting, if someone there could do a
bit of
testing in this regard, on various "moment-arm measurements",
before you would
consider the AP900 or AP1200 seriously out of balance, for the
expected
performance. For that matter, before you would consider possible
damage to the
worm gear. That might provide a good rule of thumb which could
be applied to
any OTA overload situation, to specific AP mounts.

I suppose one might say that the imbalance on any mount has
reached a
maximum, if the clutches won't hold, but some might torque down
the clutches
too tightly, even with a wrench, in order to avoid having to
shift the
weights.

Thanks for any further info,
Joe

----- Original Message -----
From: <chris1011@aol.com <mailto:chris1011%40aol.com> >
To: <ap-gto@yahoogroups.com <mailto:ap-gto%40yahoogroups.com> >
Sent: Monday, April 23, 2007 1:04 PM
Subject: Re: [ap-gto] Balance Procedure

In a message dated 4/21/2007 8:52:34 AM Central Daylight Time,
drichey@sandia.net <mailto:drichey%40sandia.net> writes:


What's the procedure for rebalancing. If I have very good
polar alignment
and a good
pointing accuracy, but need to loosen the clutces and
reblance the load due
to adding
equipment, how do I maintain my pointing model.
Your pointing model is not affected if you loosen the clutches
to rebalance.
On the other hand, why do you need to do this? I image all the
time without
ever rebalancing. It is not really necessary. I have been as
much as 8lb out
of
balance on both 900/1200 mounts, and recently ran 6lb out of
balance on my
little bitty Mach1 mount. The tracking/guiding was spot on
perfect.

Roland Christen


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