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A Mach1GTO Adventure: Does RA Gear Meshing Require Generating a New PEC?

Ben Koltenbah
 

Greetings, AP mount users and (in my case) abusers!

Last night, I rediscovered, after several years of neglect, the need to adjust the gear meshing on my Mach1GTO.  After watching my guiding performance slowly deteriorate over the summer, followed by a particularly disastrous night watching the DEC guiding oscillate like a freshman physics class demonstration on periodic motion, the epiphany was conjured from the deep, increasingly inaccessible recesses of my mind that I should re-mesh the DEC gearing using the prescribed method from the AP documentation.  Prior to that, I meandered on an embarrassingly long and futile journey inspecting and adjusting all other possible contributors to this DEC bouncing, including checking for dragging cables over every cable that could be dragged, shifting of center of gravity of every part that could be shifted, tweaking of every PHD2 software setting that could be tweaked.  In the end, and after less than five minutes of effort, I re-meshed the DEC worm gear, armed only with my 5/32" hex wrench.  Starting the guiding anew, a feeling of unbridled glee washed over me once I saw the DEC oscillations were now replaced by excellent, gently dampened randomized performance.  But this feeling was soon replaced by shame and anger at having forgotten to do this re-meshing months earlier when the problem first arose.  Now I have settled on the feeling of quiet acceptance and satisfaction.  Life will go on.

Here are a couple of screen captures from PHD Log Viewer that show the performance just before and after the DEC gear mesh adjustment.





And the following shows a close-up of the imaged stars around the center of M33 before and after the adjustment with guiding on.  I have zoomed in quite far to demonstrate the improvement.



Now I turn my attention to the RA gear meshing.  I wish to adjust this as well since I realize just how long it's been since I last worked on it that I forgot about the existence of worm gear meshing altogether.  My latest guiding curves indicate that the RA axis now under-performs the DEC axis, although not nearly as badly as the DEC misbehaved before.  Will adjusting the RA worm gear require that a new periodic error correction (PEC) curve be generated?  The AP documentation noted that if I opened the RA gear box and turned the gears by hand, I would need to mark and return them to their original position or risk invalidating the current PEC.  But what about the mesh adjustment procedure?  I'd very much appreciate your advice on this.

Thank you for your attention to this matter, and I look forward to your helpful comments.

Best Regards,
Ben

Chris White
 

Ben,

You probably don't need to remesh RA unless you have a performance problem. RA doesn't reverse direction like DEC so reasonable amount of backlash won't be a problem. 

That said, it's not a bad idea to refresh your REC curve every few years of normal use as your mount wears a little. 

Before doing anything, you can use penpro to test your curve. That test should give you an indication of the state of things...
Chris White
 

Oh, and remeshing probably won't require a new curve, as long as you don't rotate the worm on its own.   Generating a new PEC curve is super easy though, so I wouldn't hesitate to do so, especially since you are noticing a little performance drop. 

TBH, I'd test and possibly make a new curve before meshing RA. You can also test the mesh by gently rocking the axis. Do you get any movement?  If there is play, the mesh is a little loose. 
Bill Long
 

No, it does not. As long as you do not move the RA spur gears manually your PEC Curve is fine. 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ben Koltenbah <benjamin.e.c.koltenbah@...>
Sent: Sunday, November 13, 2022 4:21 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: [ap-gto] A Mach1GTO Adventure: Does RA Gear Meshing Require Generating a New PEC?
 
Greetings, AP mount users and (in my case) abusers!

Last night, I rediscovered, after several years of neglect, the need to adjust the gear meshing on my Mach1GTO.  After watching my guiding performance slowly deteriorate over the summer, followed by a particularly disastrous night watching the DEC guiding oscillate like a freshman physics class demonstration on periodic motion, the epiphany was conjured from the deep, increasingly inaccessible recesses of my mind that I should re-mesh the DEC gearing using the prescribed method from the AP documentation.  Prior to that, I meandered on an embarrassingly long and futile journey inspecting and adjusting all other possible contributors to this DEC bouncing, including checking for dragging cables over every cable that could be dragged, shifting of center of gravity of every part that could be shifted, tweaking of every PHD2 software setting that could be tweaked.  In the end, and after less than five minutes of effort, I re-meshed the DEC worm gear, armed only with my 5/32" hex wrench.  Starting the guiding anew, a feeling of unbridled glee washed over me once I saw the DEC oscillations were now replaced by excellent, gently dampened randomized performance.  But this feeling was soon replaced by shame and anger at having forgotten to do this re-meshing months earlier when the problem first arose.  Now I have settled on the feeling of quiet acceptance and satisfaction.  Life will go on.

Here are a couple of screen captures from PHD Log Viewer that show the performance just before and after the DEC gear mesh adjustment.





And the following shows a close-up of the imaged stars around the center of M33 before and after the adjustment with guiding on.  I have zoomed in quite far to demonstrate the improvement.



Now I turn my attention to the RA gear meshing.  I wish to adjust this as well since I realize just how long it's been since I last worked on it that I forgot about the existence of worm gear meshing altogether.  My latest guiding curves indicate that the RA axis now under-performs the DEC axis, although not nearly as badly as the DEC misbehaved before.  Will adjusting the RA worm gear require that a new periodic error correction (PEC) curve be generated?  The AP documentation noted that if I opened the RA gear box and turned the gears by hand, I would need to mark and return them to their original position or risk invalidating the current PEC.  But what about the mesh adjustment procedure?  I'd very much appreciate your advice on this.

Thank you for your attention to this matter, and I look forward to your helpful comments.

Best Regards,
Ben

Bill Long
 

Its all about the movement of the gears, which turn the worm against the wheel. As long as those do not move, you are fine. 

I posted this same info about 45 minutes ago. Unfortunately, it has not landed on the group yet.

From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Chris White <chris.white@...>
Sent: Sunday, November 13, 2022 8:32 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] A Mach1GTO Adventure: Does RA Gear Meshing Require Generating a New PEC?
 
Ben,

You probably don't need to remesh RA unless you have a performance problem. RA doesn't reverse direction like DEC so reasonable amount of backlash won't be a problem. 

That said, it's not a bad idea to refresh your REC curve every few years of normal use as your mount wears a little. 

Before doing anything, you can use penpro to test your curve. That test should give you an indication of the state of things...
Roland Christen
 

Mesh doesn't change PE.

Rolando



-----Original Message-----
From: Ben Koltenbah <benjamin.e.c.koltenbah@...>
To: main@ap-gto.groups.io
Sent: Sun, Nov 13, 2022 6:21 pm
Subject: [ap-gto] A Mach1GTO Adventure: Does RA Gear Meshing Require Generating a New PEC?

Greetings, AP mount users and (in my case) abusers!

Last night, I rediscovered, after several years of neglect, the need to adjust the gear meshing on my Mach1GTO.  After watching my guiding performance slowly deteriorate over the summer, followed by a particularly disastrous night watching the DEC guiding oscillate like a freshman physics class demonstration on periodic motion, the epiphany was conjured from the deep, increasingly inaccessible recesses of my mind that I should re-mesh the DEC gearing using the prescribed method from the AP documentation.  Prior to that, I meandered on an embarrassingly long and futile journey inspecting and adjusting all other possible contributors to this DEC bouncing, including checking for dragging cables over every cable that could be dragged, shifting of center of gravity of every part that could be shifted, tweaking of every PHD2 software setting that could be tweaked.  In the end, and after less than five minutes of effort, I re-meshed the DEC worm gear, armed only with my 5/32" hex wrench.  Starting the guiding anew, a feeling of unbridled glee washed over me once I saw the DEC oscillations were now replaced by excellent, gently dampened randomized performance.  But this feeling was soon replaced by shame and anger at having forgotten to do this re-meshing months earlier when the problem first arose.  Now I have settled on the feeling of quiet acceptance and satisfaction.  Life will go on.

Here are a couple of screen captures from PHD Log Viewer that show the performance just before and after the DEC gear mesh adjustment.





And the following shows a close-up of the imaged stars around the center of M33 before and after the adjustment with guiding on.  I have zoomed in quite far to demonstrate the improvement.



Now I turn my attention to the RA gear meshing.  I wish to adjust this as well since I realize just how long it's been since I last worked on it that I forgot about the existence of worm gear meshing altogether.  My latest guiding curves indicate that the RA axis now under-performs the DEC axis, although not nearly as badly as the DEC misbehaved before.  Will adjusting the RA worm gear require that a new periodic error correction (PEC) curve be generated?  The AP documentation noted that if I opened the RA gear box and turned the gears by hand, I would need to mark and return them to their original position or risk invalidating the current PEC.  But what about the mesh adjustment procedure?  I'd very much appreciate your advice on this.

Thank you for your attention to this matter, and I look forward to your helpful comments.

Best Regards,
Ben

--
Roland Christen
Astro-Physics
Ben Koltenbah
 

Thank you, Chris, Bill and Roland for your unanimous response to my question about re-meshing RA and retaining the PEC.  I am so glad that I posted this question here and not on a popular forum that shall remain nameless.  The latter can yield good advice, however often at a low SNR.

I will consider re-meshing the RA tomorrow afternoon, although I'm not sure I really need it at this time.

This week has rare, clear November nights in the Pacific Northwet, and I've been enjoying my nice, round stars post DEC meshing.

Best Regards,
Ben
Bill Long
 

No problem, Ben.

Glad to hear you are able to take advantage of the nights we have had here as of late. I am up North in Snohomish, WA and not only have we had rare clear skies, the seeing has been pretty darn good for winter time! 

As for meshing, if you are not seeing any problems that you can correlate to the RA mesh, I would not bother with it. RA does not change directions as you track the sky or guide the mount. It will only speed up and slow down. If you grab the counter weight shaft and wiggle it with the pressure of a single finger and do not detect any significant movement -- it is probably fine. I think I read in one of the AP meshing docs that RA having a tiny bit of wiggle is better than the mesh being too tight.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ben Koltenbah <benjamin.e.c.koltenbah@...>
Sent: Tuesday, November 15, 2022 6:51 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] A Mach1GTO Adventure: Does RA Gear Meshing Require Generating a New PEC?
 
Thank you, Chris, Bill and Roland for your unanimous response to my question about re-meshing RA and retaining the PEC.  I am so glad that I posted this question here and not on a popular forum that shall remain nameless.  The latter can yield good advice, however often at a low SNR.

I will consider re-meshing the RA tomorrow afternoon, although I'm not sure I really need it at this time.

This week has rare, clear November nights in the Pacific Northwet, and I've been enjoying my nice, round stars post DEC meshing.

Best Regards,
Ben

Ben Koltenbah
 

Bill:

I forgot that you are just a bit north of me here in the Puget Sound area.  Yes, I, too have been enjoying the better-than-usual seeing.  Looks like we'll get a few more clear nights before the rains return.

Ben
Bill Long
 

For sure. Clear skies in November are rare. Glad you are able to get some data during this stretch.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ben Koltenbah <benjamin.e.c.koltenbah@...>
Sent: Wednesday, November 16, 2022 6:23 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] A Mach1GTO Adventure: Does RA Gear Meshing Require Generating a New PEC?
 
Bill:

I forgot that you are just a bit north of me here in the Puget Sound area.  Yes, I, too have been enjoying the better-than-usual seeing.  Looks like we'll get a few more clear nights before the rains return.

Ben

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