PEM Curve vs. Worm Gear Position


billk@...
 

I just started doing some astrophotography with my new 1100 and I have been reading up on PEM. Since I'm new to PEM and I cannot seem to find an answer to my simple question, I figured I would just ask it here. I'm curious if there is anything about the PEM curve application that is affected when the worm gears are disengaged from the RA/DEC drive gears for checking balance etc.? Does the mount's servo system have sensors to know the exact position of the worm gears such that there are no phasing issues?


Bill Long
 

No, disengaging the worm for balance will not cause a problem with your PEM Curve. 


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of billk@... <billk@...>
Sent: Tuesday, September 7, 2021 8:55 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: [ap-gto] PEM Curve vs. Worm Gear Position
 
I just started doing some astrophotography with my new 1100 and I have been reading up on PEM. Since I'm new to PEM and I cannot seem to find an answer to my simple question, I figured I would just ask it here. I'm curious if there is anything about the PEM curve application that is affected when the worm gears are disengaged from the RA/DEC drive gears for checking balance etc.? Does the mount's servo system have sensors to know the exact position of the worm gears such that there are no phasing issues?


W Hilmo
 

The interface between the worm and the wheel (which is what you are affecting when you balance) has a 24 hour period.? This is not something that you need to worry about with PEM.

The key to knowing whether you need to redo PEM or not is knowing whether the mount can keep track of the worm position.? If you make any adjustments to the spur gears inside the gearbox, the mount will not know about the new position, so you would need to redo PEM after such an adjustment.

-Wade

On 9/7/21 10:51 AM, Bill Long wrote:
No, disengaging the worm for balance will not cause a problem with your PEM Curve.?


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of billk@... <billk@...>
Sent: Tuesday, September 7, 2021 8:55 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: [ap-gto] PEM Curve vs. Worm Gear Position
?
I just started doing some astrophotography with my new 1100 and I have been reading up on PEM. Since I'm new to PEM and I cannot seem to find an answer to my simple question, I figured I would just ask it here. I'm curious if there is anything about the PEM curve application that is affected when the worm gears are disengaged from the RA/DEC drive gears for checking balance etc.? Does the mount's servo system have sensors to know the exact position of the worm gears such that there are no phasing issues?


billk@...
 
Edited

Thanks Bill. I found this under a PEM topic and it was just the technical rationale I was looking for. Just happened to find it after posting:

And here are some more great and exclusive features of AP electronics that AP doesn't bother to mention in their literature or specifications:
 
A. Power-loss detection and data preservation. AP servo controllers can detect when power has been lost/cut and by using a special "brownout protection circuit" they quickly save the worm gear angle, worm wheel angle and spur gear train rotation position to NVRAM. That way the controllers know exactly where the spur and worm gears and wheels are positioned when power is restored. This is how the PEM data is kept in sync and how the controller already knows where the mount is pointed when it is powered up. Of course if a user is doing portable setups and/or the clutches are opened, the controller won't know if the OTA is pointing to stuff accurately or not. A single Calibration/Sync will fix that, when needed. This is also a great feature at star parties and outreach events. If someone kicks out your power connection, all you have to do is restore power, initialize the CP1/2/3/4 servo controller (automatic with the AP hand controller) and do another GOTO the object to get it back in the center of the eyepiece and track it 

Thanks for the quick answers - 

Bill K.