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CEM60 Mount

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54 replies to this topic

#51 JoeR

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Posted 10 January 2016 - 12:40 PM

I've been engaging the clutches until they stop, not tightening down, and leave them there instead of doing the 1/4 turn backwards. It's been working well for me no loud noises since and tracking has been good. Also no wobbling in the Dec or RA axis.



#52 neptun2

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Posted 29 January 2016 - 06:46 PM

Same for me. The thing with the 1/4 turn back was with the first test samples. After that for the production run clutch was reworked. I also turn the clutch till it stops. I do not tighten further applying force and this works very well for me. Quiet and good tracking and also easier instead of tightening fully and turning back.



#53 Tim C

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Posted 30 January 2016 - 09:24 AM

Usually, I engage the gears until they stop.  However, you don't crank down on it or you will force the gears together too tightly and they will bind just like on any other mount when adjusting the worm engagement.  I tighten ccw until I just feel them touch using very light finger tip pressure. For the last few sessions, I have taken to backing off a bit (about 1/8 turn). I haven't noticed any difference in RA tracking when doing that but I think *MAYBE* declination backlash is lessened when doing the 1/8 turn back.  By the way, you're not creating a partial disengagement when you back off 1/4 or 1/8 turn, the gears are still engaged with the magnetic force.  The disengagement occurs when you fully turn the knob all the way back cw and the gears are then pulled away and lifted off one another at the end of the cw turn.  You can feel the point where the gears are lifted apart when you are turning to fully disengage.. before that point the gears are still fully meshed together by the magnet force.  A guy who took apart the mount described this very well in the iOptron yahoo group.

 

I'm still on the fence about the whole magnetic gear thing.  My mount performs very well with PE peak to peak at about 5 arc sec and guides very well; however, I just don't know if the magnetic gears contribute to that or not.  The mount swings very freely when the gears are totally disengaged which makes achieving just the right balance (or desired imbalance) very easy so I like that part.


Edited by Tim C, 30 January 2016 - 09:31 AM.

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#54 HxPI

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Posted 30 January 2016 - 11:22 AM

I tried to "feel" for the right tightening tension last night and it was hit and miss. It worked for a bit but then the motor seized up midway during a slew. Also when this happens, it appears the zero position is thrown off. That's a showstopper!! I just don't have the knack for setting this thing correctly! So I'll stick with the full tighten and 1/4 turn back method until a better and more reliable method can be found. I don't like this design because it's not definite. There's just too much fiddling for something that should be either engaged or disengaged. Also I'm still not convinced that backlash and tracking are not affected by the 1/4 turn back method. Perhaps a stopper can be installed at the right place on the shaft to set it just right and prevent further tightening when engaged. I do like the frictionless freedom when disengaged so that's a good feature. No reason we can't have it both ways!

 

I did appreciate the detailed description of what is going on under the hood. It helps give a better understanding of how this mount works, which I feel is unfortunately very necessary to work out all the irregularities!

 

Thanks for sharing.

 

Ciao,

Mel


Edited by HxPI, 30 January 2016 - 11:31 AM.


#55 Tim C

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Posted 30 January 2016 - 12:41 PM

Strange how this seems to differ from one mount to the next.  Luckily, mine doesn't seem to be too sensitive to the exact location unless it's over tightened... that is the one thing to avoid for sure so I'd err on the side of backing off very slightly to ensure that doesn't happen.  It was enlightening to me to learn that backing off on the knob a little doesn't disengage or pull the gears away but it does help avoid the possibility of being overly tight which is a no-no so I think I'm sticking with my current approach of backing off 1/8 of a turn or so especially since declination backlash appears to be minimized when doing that on my mount.

 

Here is the link to the yahoo groups thread that I mentioned.  I started the topic about an issue I was seeing declination guiding.  I ultimately figured out that I should never balance nose heavy and always balance camera heavy especially near the zenith.  Or at least I think that was the resolution because my original issue that I saw a couple of times hasn't recurred since with probably 60 hours of imaging.  See the posts by Gregory in the thread.

 

https://groups.yahoo...ns/topics/12166

 

 

I tried to "feel" for the right tightening tension last night and it was hit and miss. It worked for a bit but then the motor seized up midway during a slew. 


Edited by Tim C, 30 January 2016 - 12:42 PM.



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