Re: AP900GTO - DEC stiffness


Howard Hedlund
 

Since the backlash you describe is in RA, it is not as critical to
remove it. The 600E mounts are a bit trickier to get a perfect gear
mesh, but they are still very high precision mounts. If you felt the
backlash in dec, I would say to go for it and try to remesh. As it is,
the question is "How much do you enjoy tinkering?"



Mag. 7 skies!



Howard Hedlund

Astro-Physics, Inc.

815-282-1513

________________________________

From: ap-gto@... [mailto:ap-gto@...] On Behalf
Of tomb1818
Sent: Sunday, March 21, 2010 4:39 PM
To: ap-gto@...
Subject: [ap-gto] Re: AP900GTO - DEC stiffness






Hi Howard,
Does the precision apply to mounts like the 600? I have a small amount
of backlash and was wondering if it would be useful to adjust it out( 2
mm at the end of the counterweight shaft.
Thanks

--- In ap-gto@... <mailto:ap-gto%40yahoogroups.com> ,
"Howard" <howard@...> wrote:

Good Morning Stefano!



Are you using guiding software that employs the ASCOM driver? If so,
are you using the old driver from the ASCOM website - v. 4.1.25 - or
are
you using our new driver - v. 4.99.58 - available here:

http://www.gralak.com/apdriver <http://www.gralak.com/apdriver>

The reason I ask is that the old driver had a default backlash setting
that could be overriding whatever you might have set with the keypad.
I
can't count the number of times this has been an issue, and it almost
always presents itself as oscillations when guiding. Let's first
verify
that the backlash setting really and truly is at zero!



I would not loosen what sounds like an excellent gear mesh. Think of
it this way: If your car's right front wheel is out of alignment and
is
pulling the car to the right, you can correct this by lowering the
tire
pressure in the left front tire until the car tracks in a straight
line.
You may have made your car go straight, but this probably isn't the
best
solution. You will find that your 900GTO has enough mechanical
precision that the gear mesh can be adjusted to a level where backlash
is of little significance. Most of our most experienced AP family
members find that they simply don't need to use backlash compensation.



Mag. 7 skies!



Howard Hedlund

Astro-Physics, Inc.

815-282-1513

________________________________

From: ap-gto@... <mailto:ap-gto%40yahoogroups.com>
[mailto:ap-gto@... <mailto:ap-gto%40yahoogroups.com> ] On
Behalf
Of Stefano Cancelli
Sent: Friday, March 19, 2010 8:33 AM
To: ap-gto@... <mailto:ap-gto%40yahoogroups.com>
Subject: Re: [ap-gto] AP900GTO - DEC stiffness





Thanks, Rolando. I found the pdf's on the site that show the clutch
replacement procedure and the special extraction tool. This pretty
much
answers my question as it appears its not an uncommon problem and one
that
is easily remedied. I wasnt' sure if the stiffness was coming from the
clutches not being disengaged fully or if it was some other mechanical
binding problem from the axis itself.

Another imaging session last night and still the occasional ping pong
after
dithering guider move between exposures. Once it settles however, it
will
make dec correction happily for long exposures without oscillation.
I'm
wondering if perhaps the worm mesh in DEC might be a little too tight
as
there doesn't seem to be any backlash whatsover in DEC. I know it
might
seem
counterproductive to think a tiny bit of backlash is a good thing, but
its
fairly easy to handle.

Cheers,
Stef.

On Fri, Mar 19, 2010 at 4:06 AM, <chris1011@...
<mailto:chris1011%40aol.com> > wrote:



In a message dated 3/18/2010 6:30:03 P.M. Central Daylight Time,
scancelli@... <mailto:scancelli%40treblestef.com> writes:

This kind of behaviour seems like stiction to me and I'm wondering
if
the
DEC stiffness is contributing to this.
Howard can answer you about the clutches being stiff and how to
remedy
that. However, be assured that this has nothing to do with your
guiding.
Whether the clutches are loose or fully locked has no effect
whatsoever on
guiding.

Rolando






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