PSA- Check your gear mesh! (Older mounts)


Chris White
 

The other night my guiding went haywire using my 900GTO.  It's worked flawlessly for several months so I initially thought I was having a software problem.  Essentially, after about 60 seconds of guiding dec would drift a little bit and despite PHD sending corrections, it would not respond.  To compound the issue, not only was DEC calibration failing in PHD, but also RA was requiring about 25 steps to clear the backlash. 

I spend a couple of hours debugging software, trying to see if APPC model correction could have impacted it.  I also changed PHD versions, and rebooted gear several times.  I checked my balance and fine tuned... I dialed in my PA (observatory mounted) but nothing seemed to work.

My last ditch was to see if there was a backlash issue, which in hindsight based on the behavior should have been my first check.  Sure enough, there was wiggle in DEC.  RA was solid.  The locking bolts for the motor/gearbox were gorilla tight, but following the AP PDF I remeshed in about 30 seconds and all of my problems were solved!  Gotta love this user friendly design to allow a quick and easy field adjustment.  In the PDF it explained that seasonally the mesh may need to be tweaked, so I assume that my wild Vermont temperature swings led to this. 

Well, now I know!  Of course, those of you who have mounts that automesh dont need to worry about this, but thought I would tell the story as there are a TON of older mounts out there that are faithfully performing like a champ!


Steven Panish
 

See my post from last night!  A loose DEC worm spur-gear lockscrew gives the same symptoms, except since the mesh is still good, you won't get any shaft wiggle.  Slow rates just take forever to turn the shaft enough to get rid of the play.  Guiding corrections will fail to do anything.  Just wish I hadn't ordered the y-cable.

Steve

On Sat, Aug 7, 2021 at 8:56 AM Chris White <chris.white@...> wrote:
The other night my guiding went haywire using my 900GTO.  It's worked flawlessly for several months so I initially thought I was having a software problem.  Essentially, after about 60 seconds of guiding dec would drift a little bit and despite PHD sending corrections, it would not respond.  To compound the issue, not only was DEC calibration failing in PHD, but also RA was requiring about 25 steps to clear the backlash. 

I spend a couple of hours debugging software, trying to see if APPC model correction could have impacted it.  I also changed PHD versions, and rebooted gear several times.  I checked my balance and fine tuned... I dialed in my PA (observatory mounted) but nothing seemed to work.

My last ditch was to see if there was a backlash issue, which in hindsight based on the behavior should have been my first check.  Sure enough, there was wiggle in DEC.  RA was solid.  The locking bolts for the motor/gearbox were gorilla tight, but following the AP PDF I remeshed in about 30 seconds and all of my problems were solved!  Gotta love this user friendly design to allow a quick and easy field adjustment.  In the PDF it explained that seasonally the mesh may need to be tweaked, so I assume that my wild Vermont temperature swings led to this. 

Well, now I know!  Of course, those of you who have mounts that automesh dont need to worry about this, but thought I would tell the story as there are a TON of older mounts out there that are faithfully performing like a champ!


Christopher Erickson
 

I think everyone should have a spare Y-cable and power cable in their kit.

-Christopher Erickson
Observatory engineer
Waikoloa, HI 96738
www.summitkinetics.com
   

On Sat, Aug 7, 2021, 4:24 AM Steven Panish <scpanish@...> wrote:
See my post from last night!  A loose DEC worm spur-gear lockscrew gives the same symptoms, except since the mesh is still good, you won't get any shaft wiggle.  Slow rates just take forever to turn the shaft enough to get rid of the play.  Guiding corrections will fail to do anything.  Just wish I hadn't ordered the y-cable.

Steve

On Sat, Aug 7, 2021 at 8:56 AM Chris White <chris.white@...> wrote:
The other night my guiding went haywire using my 900GTO.  It's worked flawlessly for several months so I initially thought I was having a software problem.  Essentially, after about 60 seconds of guiding dec would drift a little bit and despite PHD sending corrections, it would not respond.  To compound the issue, not only was DEC calibration failing in PHD, but also RA was requiring about 25 steps to clear the backlash. 

I spend a couple of hours debugging software, trying to see if APPC model correction could have impacted it.  I also changed PHD versions, and rebooted gear several times.  I checked my balance and fine tuned... I dialed in my PA (observatory mounted) but nothing seemed to work.

My last ditch was to see if there was a backlash issue, which in hindsight based on the behavior should have been my first check.  Sure enough, there was wiggle in DEC.  RA was solid.  The locking bolts for the motor/gearbox were gorilla tight, but following the AP PDF I remeshed in about 30 seconds and all of my problems were solved!  Gotta love this user friendly design to allow a quick and easy field adjustment.  In the PDF it explained that seasonally the mesh may need to be tweaked, so I assume that my wild Vermont temperature swings led to this. 

Well, now I know!  Of course, those of you who have mounts that automesh dont need to worry about this, but thought I would tell the story as there are a TON of older mounts out there that are faithfully performing like a champ!


Bill Long
 

Or two mounts. 😎


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Christopher Erickson <christopher.k.erickson@...>
Sent: Saturday, August 7, 2021 8:39 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] PSA- Check your gear mesh! (Older mounts)
 
I think everyone should have a spare Y-cable and power cable in their kit.

-Christopher Erickson
Observatory engineer
Waikoloa, HI 96738
www.summitkinetics.com
   

On Sat, Aug 7, 2021, 4:24 AM Steven Panish <scpanish@...> wrote:
See my post from last night!  A loose DEC worm spur-gear lockscrew gives the same symptoms, except since the mesh is still good, you won't get any shaft wiggle.  Slow rates just take forever to turn the shaft enough to get rid of the play.  Guiding corrections will fail to do anything.  Just wish I hadn't ordered the y-cable.

Steve

On Sat, Aug 7, 2021 at 8:56 AM Chris White <chris.white@...> wrote:
The other night my guiding went haywire using my 900GTO.  It's worked flawlessly for several months so I initially thought I was having a software problem.  Essentially, after about 60 seconds of guiding dec would drift a little bit and despite PHD sending corrections, it would not respond.  To compound the issue, not only was DEC calibration failing in PHD, but also RA was requiring about 25 steps to clear the backlash. 

I spend a couple of hours debugging software, trying to see if APPC model correction could have impacted it.  I also changed PHD versions, and rebooted gear several times.  I checked my balance and fine tuned... I dialed in my PA (observatory mounted) but nothing seemed to work.

My last ditch was to see if there was a backlash issue, which in hindsight based on the behavior should have been my first check.  Sure enough, there was wiggle in DEC.  RA was solid.  The locking bolts for the motor/gearbox were gorilla tight, but following the AP PDF I remeshed in about 30 seconds and all of my problems were solved!  Gotta love this user friendly design to allow a quick and easy field adjustment.  In the PDF it explained that seasonally the mesh may need to be tweaked, so I assume that my wild Vermont temperature swings led to this. 

Well, now I know!  Of course, those of you who have mounts that automesh dont need to worry about this, but thought I would tell the story as there are a TON of older mounts out there that are faithfully performing like a champ!


Chris White
 

I dont doubt you Chris, but curious what goes wrong with the y cables?


Steven Panish
 

It's kind of expensive to just keep as a spare, but with price no object, I agree in principle!  But my mount sits in the observatory and never goes anywhere and the cable never gets exposed to light, never (in my experience) snags.  
Steve

On Sat, Aug 7, 2021 at 2:08 PM Chris White <chris.white@...> wrote:
I dont doubt you Chris, but curious what goes wrong with the y cables?


Bill Long
 

Good call-out. 

Also, if you own mounts that auto-mesh and your friends are having issues, be mindful of this. I completely forgot all about meshing needs for some of the older mounts. 😳


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Chris White <chris.white@...>
Sent: Saturday, August 7, 2021 5:56 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: [ap-gto] PSA- Check your gear mesh! (Older mounts)
 
The other night my guiding went haywire using my 900GTO.  It's worked flawlessly for several months so I initially thought I was having a software problem.  Essentially, after about 60 seconds of guiding dec would drift a little bit and despite PHD sending corrections, it would not respond.  To compound the issue, not only was DEC calibration failing in PHD, but also RA was requiring about 25 steps to clear the backlash. 

I spend a couple of hours debugging software, trying to see if APPC model correction could have impacted it.  I also changed PHD versions, and rebooted gear several times.  I checked my balance and fine tuned... I dialed in my PA (observatory mounted) but nothing seemed to work.

My last ditch was to see if there was a backlash issue, which in hindsight based on the behavior should have been my first check.  Sure enough, there was wiggle in DEC.  RA was solid.  The locking bolts for the motor/gearbox were gorilla tight, but following the AP PDF I remeshed in about 30 seconds and all of my problems were solved!  Gotta love this user friendly design to allow a quick and easy field adjustment.  In the PDF it explained that seasonally the mesh may need to be tweaked, so I assume that my wild Vermont temperature swings led to this. 

Well, now I know!  Of course, those of you who have mounts that automesh dont need to worry about this, but thought I would tell the story as there are a TON of older mounts out there that are faithfully performing like a champ!


M Hambrick
 

I set up and take down my 1100 mount every night that I use it. In doing so I found that running the Y-cable outside the mount instead of through it saves several minutes of setup and takedown time. Astro-Physics sells a longer version of the Y-cable for this purpose, but the tradeoff is that even though the cable is longer, it can still get caught on the various knobs and projections when slewing the mount. If this happens the cable can be seriously damaged.

You would be surprised how quickly a cable can get snagged when the mount is slewing at 600 or 1200X. I have learned the hard way to pay close attention to cable management and to keep a finger on the keypad stop button any time I am slewing the mount. In one incident I was slewing the mount and failed to check my camera cables. The main power cable to my camera got caught between one of the DEC axis clutch knobs and gearbox housing and it completely cut through the outer insulation and severed a couple of the individual conductors.


Christopher Erickson
 

I design, work on and maintain professional observatories for a living.

Having a periodic maintenance checklist and a thoughtful critical spares inventory is something ALL of the pro's and more experienced amateurs do.

Cables get damaged. Connectors get corroded. Hidden cable defects finally reveal themselves. Motors go bad. Encoders malfunction. Servo controllers malfunction. Software bugs reveal themselves. Having a few spare strategic cables (a very cheap investment) can significantly speed up troubleshooting and end up saving hours, days, weeks or even MONTHS of delays and associated expenses from happening.

One particular professional observatory I first worked on about 10 years ago was off-sky for 2 years. The professional staff of the observatory had struggled with getting things operational with no success. When they finally brought me in, I tracked down five different intermittent cable problems and got them back on sky in three days.

Having a critical spares inventory is a no-brainer.

"My advice is always free and worth every penny!"

-Christopher Erickson
Observatory Engineer
Summit Kinetics
Waikoloa, Hawaii


On Sat, Aug 7, 2021 at 1:37 PM Steven Panish <scpanish@...> wrote:
It's kind of expensive to just keep as a spare, but with price no object, I agree in principle!  But my mount sits in the observatory and never goes anywhere and the cable never gets exposed to light, never (in my experience) snags.  
Steve

On Sat, Aug 7, 2021 at 2:08 PM Chris White <chris.white@...> wrote:
I dont doubt you Chris, but curious what goes wrong with the y cables?