Re: DEC Crosstalk


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

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