Dec Autoguiding problem finally fixed (I think)


ancient.sull
 

In followup to the Dec autoguiding problem I was having (bad
autoguiding only in Dec, not in RA and seemingly limited to tracking
in certain parts of the sky only) I think now I had two problems:

1) I had a cable bundle dragging/catching very slightly. I have an AC
adapter (to a PDF focuser which comes with a short cord) mounted on
the side of my pier. The camera cable bundle would drag over that
adapter but only when pointing to targets in the southwest (where I
was having the trouble). Thanks to Paul Mortfield for helping me
track that down. I now have an outrigger (a wooden dowel) to hold the
cable bundle away from everything as the mount tracks.

2) My worm/worm gear mesh appears to have been a tiny bit too tight.
The mount was not responding to small AG corrections (this was
behaving differently than just backlash as I saw it, and besides, I
have very little backlash).

When you open the Dec drive to check the gears there is a spur gear
(about the size of a silver dollar) that is "on top." I could turn
that large spur gear easily, but the spur gear gives a mechanical
advantage.

When, on a second trip inside the gear box, I removed the spur gear
and tried to turn the worm itself I found I couldn't 9ie the worm was
so tight I could only rotate it with the mechanical advantage of that
larger gear). I loosened the worm/worm gear mesh the tiniest bit and
now I can rotate the worm by hand and the mount will now respond to
small Dec corrections. So I think that was the second problem.

Thanks very much to Roland in particular and to all the others who
provided useful insights in how to approach this problem logically
and step by step.

Drew Sullivan
California


Steve Peters
 

Hmm, not sure how the cable would cause a dec oscillation pattern
like you (and I) were seeing. But I'm glad you solved your problem
nonetheless. I haven't been so lucky. I adjusted my dec mesh with
instructions on the phone from Howard at AP. While it took out the
dec play I was seeing, it did not solve my dec oscillation problem.
Not sure what to try next, as it seems I've tried tweaking every
setting in Maxim. For now I'm relegated to shooting in the eastern
sky, where the dec behavior is stable.

Anyway, congrats on solving your dec problem!

Steve

http://www.picturethecosmos.com



--- In ap-gto@..., "ancient.sull" <ancient.sull@...>
wrote:

In followup to the Dec autoguiding problem I was having (bad
autoguiding only in Dec, not in RA and seemingly limited to
tracking
in certain parts of the sky only) I think now I had two problems:

1) I had a cable bundle dragging/catching very slightly. I have an
AC
adapter (to a PDF focuser which comes with a short cord) mounted on
the side of my pier. The camera cable bundle would drag over that
adapter but only when pointing to targets in the southwest (where I
was having the trouble). Thanks to Paul Mortfield for helping me
track that down. I now have an outrigger (a wooden dowel) to hold
the
cable bundle away from everything as the mount tracks.

2) My worm/worm gear mesh appears to have been a tiny bit too
tight.
The mount was not responding to small AG corrections (this was
behaving differently than just backlash as I saw it, and besides, I
have very little backlash).

When you open the Dec drive to check the gears there is a spur gear
(about the size of a silver dollar) that is "on top." I could turn
that large spur gear easily, but the spur gear gives a mechanical
advantage.

When, on a second trip inside the gear box, I removed the spur gear
and tried to turn the worm itself I found I couldn't 9ie the worm
was
so tight I could only rotate it with the mechanical advantage of
that
larger gear). I loosened the worm/worm gear mesh the tiniest bit
and
now I can rotate the worm by hand and the mount will now respond to
small Dec corrections. So I think that was the second problem.

Thanks very much to Roland in particular and to all the others who
provided useful insights in how to approach this problem logically
and step by step.

Drew Sullivan
California


Roland Christen
 

In a message dated 3/26/2008 12:30:18 AM Central Daylight Time,
capitoladude@... writes:


I haven't been so lucky. I adjusted my dec mesh with
instructions on the phone from Howard at AP. While it took out the
dec play I was seeing, it did not solve my dec oscillation problem.
Not sure what to try next, as it seems I've tried tweaking every
setting in Maxim. For now I'm relegated to shooting in the eastern
sky, where the dec behavior is stable.
Start with both Dec directions turned off to monitor the drift that you are
getting in Dec when you are shooting in the western part of the sky. Next turn
on only one Dec direction and monitor the result. Send me an E-mail to let me
know the results of these tests (please include a screen shot of your tracking
chart).

Rolando


**************
Create a Home Theater Like the Pros. Watch the video on
AOL Home.

(http://home.aol.com/diy/home-improvement-eric-stromer?video=15?ncid=aolhom00030000000001)


Roland Christen
 

In a message dated 3/26/2008 9:10:44 AM Central Daylight Time,
chris1011@... writes:


I haven't been so lucky. I adjusted my dec mesh with
instructions on the phone from Howard at AP. While it took out the
dec play I was seeing, it did not solve my dec oscillation problem.
Not sure what to try next, as it seems I've tried tweaking every
setting in Maxim. For now I'm relegated to shooting in the eastern
sky, where the dec behavior is stable.
One more thing: On the AP website under Technical Support, scroll down until
you get to the heading: "Mount Troubleshooting - For additional
troubleshooting tips, check the mount and keypad manuals." Click on: "Characterizing the Dec
Axis Motions (09-15-03) - PDF document." Follow the instructions in this PDF
to determine whether your Dec axis is moving properly. The instructions should
be plain enough for you to determine if you have a mechanical problem in this
axis. If so, then we can go to the next step.

Rolando



**************
Create a Home Theater Like the Pros. Watch the video on AOL
Home.

(http://home.aol.com/diy/home-improvement-eric-stromer?video=15?ncid=aolhom00030000000001)


Roland Christen
 

In a message dated 3/27/2008 7:41:31 PM Central Daylight Time,
capitoladude@... writes:


OK, but I've done that before, on your recommendation, and the drift
was spot-on -- no more than one pixel drift in 5 minutes with both
dec directions turned off. Turning off just one direction may have
helped some, but it wasn't practical for me because recovery from the
vibration at the end of an exposure took several minutes. I will try
these things again next time I go out (probably new Moon weekend) and
capture the screen shots.
The whole idea in this excercise it to determine whether this works or not.
Once we determine this, we go on to the next step. I cannot help out if
sequences are not tried. I cannot make heads or tails from statements such as: My
mount won't autoguide". I can, however, determine what might be wrong if specific
tests are made with specific outcomes.

Rolando


**************
Create a Home Theater Like the Pros. Watch the video on
AOL Home.
(http://home.aol.com/diy/home-improvement-eric-stromer?video=15&;
ncid=aolhom00030000000001)


Steve Peters
 

--- In ap-gto@..., chris1011@... wrote:

In a message dated 3/26/2008 12:30:18 AM Central Daylight Time,
capitoladude@... writes:


I haven't been so lucky. I adjusted my dec mesh with
instructions on the phone from Howard at AP. While it took out
the
dec play I was seeing, it did not solve my dec oscillation
problem.
Not sure what to try next, as it seems I've tried tweaking every
setting in Maxim. For now I'm relegated to shooting in the
eastern
sky, where the dec behavior is stable.
Start with both Dec directions turned off to monitor the drift that
you are
getting in Dec when you are shooting in the western part of the
sky. Next turn
on only one Dec direction and monitor the result. Send me an E-mail
to let me
know the results of these tests (please include a screen shot of
your tracking
chart).

Rolando
Roland,

OK, but I've done that before, on your recommendation, and the drift
was spot-on -- no more than one pixel drift in 5 minutes with both
dec directions turned off. Turning off just one direction may have
helped some, but it wasn't practical for me because recovery from the
vibration at the end of an exposure took several minutes. I will try
these things again next time I go out (probably new Moon weekend) and
capture the screen shots.

Thanks,

Steve


Steve Peters
 

--- In ap-gto@..., chris1011@... wrote:

In a message dated 3/26/2008 9:10:44 AM Central Daylight Time,
chris1011@... writes:


I haven't been so lucky. I adjusted my dec mesh with
instructions on the phone from Howard at AP. While it took out
the
dec play I was seeing, it did not solve my dec oscillation
problem.
Not sure what to try next, as it seems I've tried tweaking
every
setting in Maxim. For now I'm relegated to shooting in the
eastern
sky, where the dec behavior is stable.
One more thing: On the AP website under Technical Support, scroll
down until
you get to the heading: "Mount Troubleshooting - For additional
troubleshooting tips, check the mount and keypad manuals." Click
on: "Characterizing the Dec
Axis Motions (09-15-03) - PDF document." Follow the instructions in
this PDF
to determine whether your Dec axis is moving properly. The
instructions should
be plain enough for you to determine if you have a mechanical
problem in this
axis. If so, then we can go to the next step.

Rolando
OK, will do. Thanks.

Steve