DEC Crosstalk


Clayton Yendrey
 

I'm trying to get some idea/context for the issue of DEC crosstalk to the RA axis during tracking/guiding.  I see this as a topic that seems to come with different users in the Paramount forums almost continuously - in other words while user may/may not get it resolved with adjustments to worm engagement, there is usually someone else that will have a similar issue shortly, so there is never an true absence of problems being reported.  I did not see this reported as an stand alone issue when I had an EQ6R, nor when I had an Ioptron GEM45 in those respective user groups.

I'm not saying it doesn't occur, but I can't remember a specific case of someone reporting this particular issue in the AP-GTO groups.  I've seen it stated on a few occasions in the Paramount forums that all GEM mounts are subject to this problem (with the sub text that there isn't a problem with the Paramount's design).  I'm not asking about the Paramounts (although I have one while waiting for my turn at a Mach2).  

What I'm trying to gauge the accuracy of is the generalization from them that this is just something that GEM mounts have and users just need to deal with it.  Seems if that was the case, it would tend to be more visible in other forums?  So is this something that is inherent to GEM mounts / AP mounts and how prevalent is it/how is it dealt with?

 

Thanks in advance,
Clayton


Roland Christen
 

I have never seen it in any of our present mounts. It can happen if the Dec main bearings are not fully pre-loaded.

Rolando


-----Original Message-----
From: Clayton Yendrey <cyendrey@...>
To: main@ap-gto.groups.io
Sent: Wed, May 12, 2021 2:46 pm
Subject: [ap-gto] DEC Crosstalk

I'm trying to get some idea/context for the issue of DEC crosstalk to the RA axis during tracking/guiding.  I see this as a topic that seems to come with different users in the Paramount forums almost continuously - in other words while user may/may not get it resolved with adjustments to worm engagement, there is usually someone else that will have a similar issue shortly, so there is never an true absence of problems being reported.  I did not see this reported as an stand alone issue when I had an EQ6R, nor when I had an Ioptron GEM45 in those respective user groups.
I'm not saying it doesn't occur, but I can't remember a specific case of someone reporting this particular issue in the AP-GTO groups.  I've seen it stated on a few occasions in the Paramount forums that all GEM mounts are subject to this problem (with the sub text that there isn't a problem with the Paramount's design).  I'm not asking about the Paramounts (although I have one while waiting for my turn at a Mach2).  
What I'm trying to gauge the accuracy of is the generalization from them that this is just something that GEM mounts have and users just need to deal with it.  Seems if that was the case, it would tend to be more visible in other forums?  So is this something that is inherent to GEM mounts / AP mounts and how prevalent is it/how is it dealt with?
 
Thanks in advance,
Clayton

--
Roland Christen
Astro-Physics


 

Hi Clayton
>>>I'm trying to get some idea/context for the issue of DEC crosstalk to the RA axis during tracking/guiding.

How does the orthagonality of your guiding calibration look? if it's not at 90 degrees, that would cause mirroring between the axis



On Wed, May 12, 2021 at 12:59 PM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
I have never seen it in any of our present mounts. It can happen if the Dec main bearings are not fully pre-loaded.

Rolando


-----Original Message-----
From: Clayton Yendrey <cyendrey@...>
To: main@ap-gto.groups.io
Sent: Wed, May 12, 2021 2:46 pm
Subject: [ap-gto] DEC Crosstalk

I'm trying to get some idea/context for the issue of DEC crosstalk to the RA axis during tracking/guiding.  I see this as a topic that seems to come with different users in the Paramount forums almost continuously - in other words while user may/may not get it resolved with adjustments to worm engagement, there is usually someone else that will have a similar issue shortly, so there is never an true absence of problems being reported.  I did not see this reported as an stand alone issue when I had an EQ6R, nor when I had an Ioptron GEM45 in those respective user groups.
I'm not saying it doesn't occur, but I can't remember a specific case of someone reporting this particular issue in the AP-GTO groups.  I've seen it stated on a few occasions in the Paramount forums that all GEM mounts are subject to this problem (with the sub text that there isn't a problem with the Paramount's design).  I'm not asking about the Paramounts (although I have one while waiting for my turn at a Mach2).  
What I'm trying to gauge the accuracy of is the generalization from them that this is just something that GEM mounts have and users just need to deal with it.  Seems if that was the case, it would tend to be more visible in other forums?  So is this something that is inherent to GEM mounts / AP mounts and how prevalent is it/how is it dealt with?
 
Thanks in advance,
Clayton

--
Roland Christen
Astro-Physics



--
Brian 



Brian Valente


Roland Christen
 

Typically, crosstalk occurs when the Dec axis is moved slightly during guiding, and this causes a corresponding Ra movement. It typically happens when the scope is pointed toward the meridian (sometimes from zenith to the pole). The wiping action of the Dec worm against the Dec worm wheel causes the wheel to lift slightly if the Dec bearings are not highly pre-loaded. The entire worm wheel and shaft will tilt slightly back and forth as the worm gear turns in the worm wheel teeth. It's caused by friction of the worm teeth against the worm gear. This slight tilting is in the direction of RA but cannot be seen as an RA shaft motion.

Rolando

-----Original Message-----
From: Brian Valente <bvalente@...>
To: main@ap-gto.groups.io
Sent: Wed, May 12, 2021 3:05 pm
Subject: Re: [ap-gto] DEC Crosstalk

Hi Clayton
>>>I'm trying to get some idea/context for the issue of DEC crosstalk to the RA axis during tracking/guiding.

How does the orthagonality of your guiding calibration look? if it's not at 90 degrees, that would cause mirroring between the axis



On Wed, May 12, 2021 at 12:59 PM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
I have never seen it in any of our present mounts. It can happen if the Dec main bearings are not fully pre-loaded.

Rolando


-----Original Message-----
From: Clayton Yendrey <cyendrey@...>
To: main@ap-gto.groups.io
Sent: Wed, May 12, 2021 2:46 pm
Subject: [ap-gto] DEC Crosstalk

I'm trying to get some idea/context for the issue of DEC crosstalk to the RA axis during tracking/guiding.  I see this as a topic that seems to come with different users in the Paramount forums almost continuously - in other words while user may/may not get it resolved with adjustments to worm engagement, there is usually someone else that will have a similar issue shortly, so there is never an true absence of problems being reported.  I did not see this reported as an stand alone issue when I had an EQ6R, nor when I had an Ioptron GEM45 in those respective user groups.
I'm not saying it doesn't occur, but I can't remember a specific case of someone reporting this particular issue in the AP-GTO groups.  I've seen it stated on a few occasions in the Paramount forums that all GEM mounts are subject to this problem (with the sub text that there isn't a problem with the Paramount's design).  I'm not asking about the Paramounts (although I have one while waiting for my turn at a Mach2).  
What I'm trying to gauge the accuracy of is the generalization from them that this is just something that GEM mounts have and users just need to deal with it.  Seems if that was the case, it would tend to be more visible in other forums?  So is this something that is inherent to GEM mounts / AP mounts and how prevalent is it/how is it dealt with?
 
Thanks in advance,
Clayton

--
Roland Christen
Astro-Physics


--
Brian 



Brian Valente

--
Roland Christen
Astro-Physics


Clayton Yendrey
 

Ortho looked good, always has with this mount - other than indicating that I don't always have the axis of the guide camera aligned with the axis of the mount movement.  I typically try to adjust/make it perpendicular on the next calibration.  In this instance it was about (going by memory) about 3dg tilt.

To be clear, this is NOT an AP mount that I'm working with at the moment.  A comment was made about this being a general issue with GEM mounts by the Support for that mount.  Since I don't see/haven't found many/any discussions about DEC causing spike (crosstalk) in the RA across several different internet searches, I thought I'd ask the other manufacturers support directly.  Of course, doesn't hurt that I only have 22 months to go on my Mach2 waiting list...   


 

>>> other than indicating that I don't always have the axis of the guide camera aligned with the axis of the mount movement.  I typically try to adjust/make it perpendicular on the next calibration.  In this instance it was about (going by memory) about 3dg tilt.

two things

first you do not need to do this. that is the purpose of the calibration

second, if you adjust it after calibration, that invalidates the calibration

All you need to do is calibrate and leave it alone



On Wed, May 12, 2021 at 2:33 PM Clayton Yendrey <cyendrey@...> wrote:

Ortho looked good, always has with this mount - other than indicating that I don't always have the axis of the guide camera aligned with the axis of the mount movement.  I typically try to adjust/make it perpendicular on the next calibration.  In this instance it was about (going by memory) about 3dg tilt.

To be clear, this is NOT an AP mount that I'm working with at the moment.  A comment was made about this being a general issue with GEM mounts by the Support for that mount.  Since I don't see/haven't found many/any discussions about DEC causing spike (crosstalk) in the RA across several different internet searches, I thought I'd ask the other manufacturers support directly.  Of course, doesn't hurt that I only have 22 months to go on my Mach2 waiting list...   



--
Brian 



Brian Valente


Clayton Yendrey
 

Roland,
Thanks for the excellent explanation of what happens.  That would explain, I believe, the appearance of large RA spikes literally out of nowhere.  It would seem that the bearing mount/assembly, besides lacking preload, could also be insufficiently rigid as a contributing factor?

This problem is more prevalent/larger magnitude when the mount pointing at high declinations.  It was around 3 hrs before meridian flip on the target (M51).  No spikes readily apparent when guiding at Dec 0/10 minutes west of meridian but began occurring immediately after slewing to target (M51).


Clayton Yendrey
 

Brian,
I do understand that, but although I leave the mount on the pier in the backyard, I do not leave the OTA there.  For safe carrying, I have a D plate handle assembly; to use it I remove the guide camera/scope from the top D plate and install the handle to carry the OTA safely/securely.  Since I am 'disturbing' the guide scope assembly each time I mount/dismount the OTA, I perform a calibration.  On the few times I've actually had back to back viewing nights, I have left the OTA on the mount and have not recalibrated.