Kevin
Thanks for the detailed explanation (I'm going to check mine tonight). I'd
wager that this will make the 'Mapug Archives'.

Gregg Ruppel

Visit my astronomy site at:
http://www.biz1.net/~ruppelgl

----- Original Message -----
Sent: July 03, 2001 2:26 PM
Subject: [M]: Declination Looseness Problem - Solved! (long, sorry)


> My 10" f/10 LX-200 just had its first birthday and to celebrate I decided
to
> do a very minor mechanical teardown to see if I could get to the bottom of
> what I perceived to be some looseness in the declination axis. Also I
> noticed recently while set up on the superwedge some retrograde motion
when
> using the dec drive that I had never noticed before, but which only seemed
> to show up when pointed in certain directions. I felt my tracking and
> pointing was OK, but not as good as it should be compared to reports from
> other owners. In some cases, when slewing perhaps 60 degrees, I'd be off
> target by up to a degree. Not very good, but I assumed I just hadn't done
a
> careful alignment. Sometimes accuracy seemed to be much better, but not
very
> often.
>
> I should mention at this point that since the first day I set up my
LX-200,
> I noticed a "thud" or "clunk" as I moved the OTA up and down in
declination.
> If I loosened the dec clutch and rotated the OTA starting from pointing
> straight down, somewhere just above horizontal I could feel, see, and hear
a
> "thud". Having no basis for comparison, I thought this was "normal". I'm
> sure most other owners are probably laughing at me by this point, but I
> didn't know any better. I probably thought this was the "mirror flop" that
> I'd read so much about.
>
> Before I started disassembly I read up on Doc G's advice as well as all
the
> other advice I could get my hands on regarding the dec drive. I'm a bit
> mechanically challenged, so I proceeded very slowly and carefully. I
> removed the dec housing, then put the clutch knob back on and tightened
it.
> Looking for any looseness between the worm and the bull gear while rocking
> the OTA slightly, I could see none. But I was definitely moving the OTA
> slightly, perhaps one or two degrees, maybe even more. So where was the
> looseness?
>
> Finally, I noticed that as I continued rocking the OTA, there was a
definite
> motion between the OTA tube and what I'm going to call the OTA support
> bracket (not the right term I'm sure). This is the black bracket that is
> bolted to the OTA and is connected to the dec bearings, I presume. I could
> see very considerable motion (flexure) taking place between the OTA
support
> bracket on the dec motor side and the OTA itself. This is what was
allowing
> the OTA to rock even when the clutch was tightened. Definitely did not
seem
> right to me (duh).
>
> When the OTA is pointing straight down, there are three allen-head bolts
in
> this support bracket above the dec bearing, two larger, one smaller. I put
a
> wrench on the smaller of the three and tightened two full turns!! This
baby
> was loose! I could actually see the support bracket snug up to the OTA as
I
> tightened. I did not tighten for all I was worth, just to firm tightness.
> Next I checked the two larger bolts on that same side and got nearly one
> full turn on each of them. Way too loose as well! Of the three on the
other
> side (opposite the dec drive motor) the two larger ones got about 1/2 turn
> each and the smaller one on that side was already tight.
>
> Well, immediately the "thud" was gone when I rotated the OTA in
declination.
> Also the amount of play I get when I try to rock the OTA with the clutch
> tightened is much less, almost nothing compared to before. Unfortunately I
> 'm going to be clouded out for the next couple of days so it will be a
> little while before I can see how much this improves my pointing accuracy
> (and the retrograde motion problem). But I have to believe that the amount
> of flexure and looseness between the support bracket and the OTA that I
had
> before was a huge contributor to my accuracy problem.
>
> I've gone on long on this because I haven't seen this particular problem
> posted before. If I had thought to check this before, I could have found
out
> in less than one minute (without disassembling anything) that these bolts
> were loose. All you need are two proper size allen wrenches to check. I'd
> definitely recommend anyone having pointing accuracy problems to check
those
> six bolts before you do anything else.
>
> And now I know that my LX-200 is NOT supposed to go "thud".
>
> I'd be very interested to know if anyone else has come across this
problem.
>
> Clear skies,
> Kevin Wigell
>
>

View index by [date] [author] [subject]
Previous message: [M]: Declination Looseness Problem - Solved! (long, sorry), Kevin Wigell
Next message: Re: [M]: Repairing the LX200 Dec and RA drives, Bob
Previous message in thread: [M]: Declination Looseness Problem - Solved! (long, sorry), Kevin Wigell