Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

iOptron CEM60 clutch problems

astrophotography equipment mount
  • Please log in to reply
21 replies to this topic

#1 Dovakun

Dovakun

    Sputnik

  • -----
  • topic starter
  • Posts: 41
  • Joined: 16 Aug 2018

Posted 15 April 2019 - 10:03 PM

First night using the CEM60 has been less than wonderful. The mount itself has awesome features, The motors are quiet and it's built well with one exception. The **** clutch design sucks. I get that if they are too tight that they will stall the motors, but when they are loosened, slewing across the meridian seems to tighten the cluches. I tried 4 times to do a simple 3 star alignment and after slewing to the last star the motors would stall forcing me to reset the zero position and start the alignment over again. Has anyone had this issue or know of a solution? I'm beginning to wish I had gone with the CGX mount. My AVX was rock solid when aligning and slewing. You'd think a 2k dollar mount with a 60lb payload would do a better job...



#2 zakry3323

zakry3323

    Viking 1

  • *****
  • Posts: 766
  • Joined: 11 Apr 2016
  • Loc: Pittsburgh

Posted 15 April 2019 - 10:23 PM

For a clutch design they're truly awful. 

 

Thing is, they're not clutches. Coming from an AXV just like you, it's helpful for me not to even think of them as such, because they really don't like being treated as such. 

Sounds like they're just not backed off enough from the fully engaged position. I had my own first light with the CEM60 tonight and it did take some trial and error. I moved them to just starting to feel tight, then backed them off. Right around a full quarter turn for the RA axis, a little less than that for Dec. I hope you keep experimenting and enjoy some success soon. 


Edited by zakry3323, 15 April 2019 - 10:35 PM.

  • bobzeq25 likes this

#3 Dovakun

Dovakun

    Sputnik

  • -----
  • topic starter
  • Posts: 41
  • Joined: 16 Aug 2018

Posted 15 April 2019 - 10:30 PM

That's about what I did. It was fine going to Sirius but then it tightened when it went to Arcturus. I made it through the alignment checking the tension after every star and slewed to ngc4631 which it had to be off because I didn't see the Galaxy in a 2min exposure. I went to do another three star align and stalled. I'll give it 1 more try another night but it shouldn't take more than 30min to start imaging.
  • zakry3323 likes this

#4 gotak

gotak

    Surveyor 1

  • -----
  • Posts: 1653
  • Joined: 18 Sep 2016
  • Loc: Toronto, CA

Posted 15 April 2019 - 10:39 PM

You just need a bit of time. It's not a clutch in the typical sense as said(although you can get a mech eng to tell you why it is LOL).

 

There's a tread explaining what it does but I can't seem to find it. Basically, the knob has three state 1) pulling the worm off against the magnetic forces and 2) pushing on the worm into the wheel. And 3) floating not really interacting with the worm.

 

You want state 3. And you do that by  turning it all the way in but without too much forces. Basically once it hits bottom of engaged you stop. Then turn back 1/8 to 1/4 of a turn.

 

Another note, are you actually balanced and there are no tangled cables or cable tug? The steppers will stall at the drop of a hat for anything beyond firm finger pressure. You say slewing cross meridian causes a stall which makes me wonder if the issue is balance. There's no need to do east heavy with a CEM60.

 

A CGX has plenty of issues too. The clutch is the worse aspect of the CEM60 by far, once you get past it though you realized it allows prefect balancing. My real problem is their locations are not human friendly, seem more design for an octopus. ...


Edited by gotak, 15 April 2019 - 10:43 PM.

  • zjc26138, scadvice and Dovakun like this

#5 scadvice

scadvice

    Viking 1

  • *****
  • Vendors
  • Posts: 801
  • Joined: 20 Feb 2018
  • Loc: Lodi, California

Posted 15 April 2019 - 10:40 PM

They don't have a clutch rather it is magnetic. Turning the knob all the way CW until it stops...this disengages the worm. I always keep my hand on the OTA. The part you need to "learn" is re-engaging.  With my hand on the OTA I start turning the knob CCW. This will allow the magnet to pull the worm back into engagement with the gear. I rock my OTA very, very slightly back an forth in the axis I'm setting so that the worm teeth will mesh easily with the gear and I can feel any backlash. Once I cannot feel any backlash I turn the knob CCW about a half a turn more and I'm done. Every mount is a little different in the amount you turn beyond where you don't feel any play (backlash) but generally it's about 1/3rd to 3/4 turn.

 

Don't think of it as a clutch because it isn't. As I said there is no clutch. The knob  is just a method to disengage the worm from the gear then releasing the magnet to once again back to be engaged. The magnet holds the worm in place and all you are doing by turning it it CCW is allowing the magnetic force to hold the worm in place again against the gear and float with any eccentricity. The eccentricity is what is causing your problem. All mounts have this problem because gear and worm mesh has to be very close.

 

This is important to do every time you setup:  Once you have reset the worms in both axis you then slew the mount 180 degrees in from zero position in both directions on both axis. If you hear a buzzing in one or both axis then in that axis it is still not completely released so go back to it and turn the knob about a 1/8 to 1/4 more CCW. Reset Zero home position again and retest. Repeat as needed until you can slew without the stepper slipping ( The stepper slipping does not hurt anything it just loses it's position).

 

Once you understand and get use to it you'll have no problems and if you do it only will take you a minute or so to fix.


Edited by scadvice, 15 April 2019 - 11:05 PM.

  • zakry3323 likes this

#6 gotak

gotak

    Surveyor 1

  • -----
  • Posts: 1653
  • Joined: 18 Sep 2016
  • Loc: Toronto, CA

Posted 15 April 2019 - 10:48 PM

Just another note. The slewing can clatter a bit sometimes isn't always indicative of a problem. It's only an issue if returning to zero result in offset stopping location.

 

If you do the rocking part to slip the worm into place like above, be extremely careful. A bit much and you might damage the worm. DEC don't worry that can have damage and you wouldn't notice. RA is much more painful and experience. 


Edited by gotak, 15 April 2019 - 10:49 PM.


#7 Dovakun

Dovakun

    Sputnik

  • -----
  • topic starter
  • Posts: 41
  • Joined: 16 Aug 2018

Posted 15 April 2019 - 10:52 PM

You just need a bit of time. It's not a clutch in the typical sense as said(although you can get a mech eng to tell you why it is LOL).

There's a tread explaining what it does but I can't seem to find it. Basically, the knob has three state 1) pulling the worm off against the magnetic forces and 2) pushing on the worm into the wheel. And 3) floating not really interacting with the worm.

You want state 3. And you do that by turning it all the way in but without too much forces. Basically once it hits bottom of engaged you stop. Then turn back 1/8 to 1/4 of a turn.

Another note, are you actually balanced and there are no tangled cables or cable tug? The steppers will stall at the drop of a hat for anything beyond firm finger pressure. You say slewing cross meridian causes a stall which makes me wonder if the issue is balance. There's no need to do east heavy with a CEM60.

A CGX has plenty of issues too. The clutch is the worse aspect of the CEM60 by far, once you get past it though you realized it allows prefect balancing. My real problem is their locations are not human friendly, seem more design for an octopus. ...



Right. I call it a clutch because it engages the gear with the motor. It seemed to be well balanced. Everything was stationary at parallel when the motors were disengaged with the gear. I might play with that a bit. I'm not worried about cables. All the cables are running into an ASIair velcroed to the Dec plate. The rs232 cable and power are the only cables that cross the axis and they are out of the way. Balance may just be that sensitive though especially because I've only got about 20lbs on it.

#8 zakry3323

zakry3323

    Viking 1

  • *****
  • Posts: 766
  • Joined: 11 Apr 2016
  • Loc: Pittsburgh

Posted 15 April 2019 - 10:52 PM

 it shouldn't take more than 30min to start imaging.

100% agree with you. If it's defective it definitely needs to go back. 

 

During an early practice run, I noticed two things that seemed like they might affect the load on the motors gears that could cause some problems-

 

First, this thing is both amazingly easy and not especially intuitive to balance. I haven't got a best practices system down yet, but mounting the scope first with the axis disengaged feels really weird to me coming from the AVX. It also sits way further down in the tube rings due to that 22lb weight being on the front of the axis, I wasn't ready for that and it took me a fairly long time to balance. But the nice thing is that there's no stiction, so balancing can be very precise, as opposed to that AVX. I'll bet having the balance off a little bit could mess things up a bit. 

While focusing I noticed a small shift in north/south that didn't happen while I was touching the focuser. I figured I was imagining things, but then I nailed down the culprit- me, I had left the lock on the alt adjustment completely loose. 

 

Those were my first thoughts, I hope others chime in with their experiences as well!


Edited by zakry3323, 15 April 2019 - 10:58 PM.


#9 scadvice

scadvice

    Viking 1

  • *****
  • Vendors
  • Posts: 801
  • Joined: 20 Feb 2018
  • Loc: Lodi, California

Posted 15 April 2019 - 10:53 PM

I edited my first post #5 hopefully easier to read.



#10 gotak

gotak

    Surveyor 1

  • -----
  • Posts: 1653
  • Joined: 18 Sep 2016
  • Loc: Toronto, CA

Posted 15 April 2019 - 11:30 PM

Right. I call it a clutch because it engages the gear with the motor. It seemed to be well balanced. Everything was stationary at parallel when the motors were disengaged with the gear. I might play with that a bit. I'm not worried about cables. All the cables are running into an ASIair velcroed to the Dec plate. The rs232 cable and power are the only cables that cross the axis and they are out of the way. Balance may just be that sensitive though especially because I've only got about 20lbs on it.

Most people don't have perfect 3d balance. Parallel could happen if you have more weight on the bottom side of the OTA in DEC for example.

 

For RA yes it's usually easier and slight imbalance shouldn't cause any issues. These things are shipped a long way so you could have one where the worm's been knocked out of alignment or something's bent. There was one incident recently where the CEM60 had to be replaced due to a bent motor bracket, which of interest to you is that mount also stalls.

 

Don't hesitate to email iOptron. They'll likely answer within the hour. Also check if your vendor would exchange if there's an issue. 



#11 bobzeq25

bobzeq25

    Hubble

  • *****
  • Posts: 15139
  • Joined: 27 Oct 2014

Posted 15 April 2019 - 11:35 PM

If you think of them as clutches, you're headed for trouble.  They are nothing _at all_ like clutches.  Zero.  Zip.

 

The worms are intended to float under magnetic control.  The adjustment knobs simply adjust the range over which the worm is allowed to float.  That's it.  They do _not_ adjust the tension, that's set by the magnets.

 

Think of them as two washers surrounding an arm attached to the worm.  When you turn the knob to engaged (and you should _never_ tighten them, engaged is _very_ lightly bottomed, turning it harder does _nothing_), the outer washer is holding the worm against the wheel, not allowing any float.

 

When you turn it out slightly (1/8-1/4 turn, you should not need any more), the worm floats (between the washers).  The exact amount you turn is not at all critical.  This is operating position.

 

Turn it further (on mine it's about 1 full turn, yours may differ), and the inner washer pulls the worm off the wheel.  This is the danger zone.  When the worm is fully pulled off the wheel, the scope swings very freely, it needs to be held on to.  If the worm is pulled partially off, force will skate he worm across the wheel, which can't be good.  Once again, once they're very lightly bottomed at disengaged, tightening them does absolutely _nothing_.

 

They adjust distance, _not_ force.  Screwing them tightly does not change the distance.

 

iOptron appears to have given up on people actually reading the manual, the CEM120 and CEM40 use a different approach.


Edited by bobzeq25, 15 April 2019 - 11:44 PM.


#12 bmhjr

bmhjr

    Apollo

  • ****-
  • Posts: 1038
  • Joined: 02 Oct 2015
  • Loc: Colorado

Posted 16 April 2019 - 01:27 AM

There is a PDF in this thread that will help you see what is going on with the adjustment knobs:

 

https://www.cloudyni...t/#entry8149354


  • bobzeq25 likes this

#13 Dovakun

Dovakun

    Sputnik

  • -----
  • topic starter
  • Posts: 41
  • Joined: 16 Aug 2018

Posted 16 April 2019 - 07:18 AM

I have read the manual and that may be why I'm having issues with the mount. I get that the bolt that moves the worm gear isn't a clutch in the traditional sense but it is easier to say it's a clutch since that's the job it is replacing, Engaging and Disengaging from the motor. That being said (after cooling down from the frustration) I set everything up this morning. Balanced, and ran through a 3 star align and slewed to several object that are up. Luckily no stalling. I blame the manual a bit because they say that if the gear is not disengaged it can cause damage to worm gear which would not be covered under warranty. So I did one axis at a time at max speed to make sure it didn't stall or grind. It seems that the gears move a bit differently when slewing however since both axis are moving at the same time. Right now it seems good but I noticed that during balancing that my scope wants to remain horizontal and leans east. I have seen one person add washers to the west side of the mount to compensate for this but is this necessary? Listening to the mount it seems to struggle going from east to west (the best way to describe it is like a soft Chewbacca sound).

 

For now I will just need to wait for some clear skies to test the accuracy of the mount. I'm putting tape on the gear and the mount to make sure I go back to the same spot. I like the idea of the magnetic engagement system but in practice it kinda sucks since it's so sensitive and varies so much between mounts and payloads. My mount with the ED102 seems to need a 1/4 turn for RA and just under 3/4 for the DEC.

 

IMG_20190416_072957.jpg

 



#14 scadvice

scadvice

    Viking 1

  • *****
  • Vendors
  • Posts: 801
  • Joined: 20 Feb 2018
  • Loc: Lodi, California

Posted 16 April 2019 - 10:49 AM

Mine leans West slightly but it doesn't seem to effect guiding.



#15 bobzeq25

bobzeq25

    Hubble

  • *****
  • Posts: 15139
  • Joined: 27 Oct 2014

Posted 16 April 2019 - 11:08 AM

I have read the manual and that may be why I'm having issues with the mount. I get that the bolt that moves the worm gear isn't a clutch in the traditional sense but it is easier to say it's a clutch since that's the job it is replacing, Engaging and Disengaging from the motor. That being said (after cooling down from the frustration) I set everything up this morning. Balanced, and ran through a 3 star align and slewed to several object that are up. Luckily no stalling. I blame the manual a bit because they say that if the gear is not disengaged it can cause damage to worm gear which would not be covered under warranty. So I did one axis at a time at max speed to make sure it didn't stall or grind. It seems that the gears move a bit differently when slewing however since both axis are moving at the same time. Right now it seems good but I noticed that during balancing that my scope wants to remain horizontal and leans east. I have seen one person add washers to the west side of the mount to compensate for this but is this necessary? Listening to the mount it seems to struggle going from east to west (the best way to describe it is like a soft Chewbacca sound).

 

For now I will just need to wait for some clear skies to test the accuracy of the mount. I'm putting tape on the gear and the mount to make sure I go back to the same spot. I like the idea of the magnetic engagement system but in practice it kinda sucks since it's so sensitive and varies so much between mounts and payloads. My mount with the ED102 seems to need a 1/4 turn for RA and just under 3/4 for the DEC.

 

attachicon.gif IMG_20190416_072957.jpg

3/4 turn is a bizarre amount.  I've never heard of anyone doing that.  Unless they've changed the screw thread (unlikely), I do not see how that possibly be correct.  You're getting close to no man's land, where things can go really bad.  The manual:

 

"The Gear Switch MUST NOT be left in a position that is in between  the  Engaged  and  Disengaged  positions.  Setting  the  Gear Switch  in  between  states  may damage the worm or worm wheel."

 

That's all the manual is warning you about, operating where the inner washer is pulling the worm off the wheel.  On my mount 3/4 turn would be getting close, maybe even there.  Keep it to no more than 1/4 turn, no worries.  The manual.

 

"If the mount motor has “grinding” sound (which is not harmful) while slewing, the gear switch is too tight. Release 1/16 to 1/8 turn (Clockwise) and check it again."

 

The adjustment is not very sensitive.  The worm doesn't need to float much.  The spacing between the washers is significantly larger than the float.

 

I'd email iOptron and ask what's up.  You should _not_ have to turn 3/4 turn to stop the mount from stalling.  If it does stall, the sound is unmistakable, and not soft (which is normal, as is some clicking when the autoguider kicks in).  Maybe something is broken.

 

Preventing stall is the main reason you turn the screw out, at all.


Edited by bobzeq25, 16 April 2019 - 11:19 AM.

  • zakry3323 and Dovakun like this

#16 zakry3323

zakry3323

    Viking 1

  • *****
  • Posts: 766
  • Joined: 11 Apr 2016
  • Loc: Pittsburgh

Posted 16 April 2019 - 12:27 PM

I'd email iOptron and ask what's up.  You should _not_ have to turn 3/4 turn to stop the mount from stalling.  If it does stall, the sound is unmistakable, and not soft (which is normal, as is some clicking when the autoguider kicks in).  Maybe something is broken.

 

Preventing stall is the main reason you turn the screw out, at all.

Thanks for that tip! I did notice a click with every North/South step the autoguider made while calibration was taking place. There didn't seem to be anything wrong, but it's good to know that it's normal to be hearing that. 


  • bobzeq25 likes this

#17 Dovakun

Dovakun

    Sputnik

  • -----
  • topic starter
  • Posts: 41
  • Joined: 16 Aug 2018

Posted 16 April 2019 - 02:00 PM

Yeah the stalling sound is super loud and high pitched. It's odd that the sound I heard it's only when it moves in one direction though. When slewing from west to east it sounded fine. Quite and smooth. When it slows down for the approach it sounds like it grinds a bit but I've heard that on other CEM60 mounts. I'll try to record it and put it on youtube later. I expected slight clicking when making small adjustments either while either autoguiding or doing small alignments.



#18 Dovakun

Dovakun

    Sputnik

  • -----
  • topic starter
  • Posts: 41
  • Joined: 16 Aug 2018

Posted 17 April 2019 - 02:10 AM

I made it out last night just long enough to test the alignment. Luckily no stalling. The mount still has some odd noises moving from East to West but it doesn't sound harsh. The only problem I have at this point is accuracy. It is consistently off by about 30 arcminutes even after a 3 star align. GPS pulls coordinates and time is correct. I also use a polemaster so polar alignment is perfect. The good news is that there is zero backlash on this mount unlike the AVX. If I can just figure out how to improve the accuracy I'll finally be able to start imaging.

#19 zakry3323

zakry3323

    Viking 1

  • *****
  • Posts: 766
  • Joined: 11 Apr 2016
  • Loc: Pittsburgh

Posted 17 April 2019 - 07:53 AM

Are you using SGP? I haven't gotten that far yet, but I plan to forego star alignment and plate solve using platesolve2.

#20 OldManSky

OldManSky

    Viking 1

  • -----
  • Posts: 602
  • Joined: 03 Jan 2019
  • Loc: Valley Center, CA USA

Posted 17 April 2019 - 08:49 AM

I made it out last night just long enough to test the alignment. Luckily no stalling. The mount still has some odd noises moving from East to West but it doesn't sound harsh. The only problem I have at this point is accuracy. It is consistently off by about 30 arcminutes even after a 3 star align. GPS pulls coordinates and time is correct. I also use a polemaster so polar alignment is perfect. The good news is that there is zero backlash on this mount unlike the AVX. If I can just figure out how to improve the accuracy I'll finally be able to start imaging.

Have you checked to see if you have cone error with your scope setup?  

That's about the only thing I can think of that might affect pointing accuracy after a 3-star alignment...well, that or some flexure of the scope mounting as you move to different parts of the sky.



#21 bobzeq25

bobzeq25

    Hubble

  • *****
  • Posts: 15139
  • Joined: 27 Oct 2014

Posted 17 April 2019 - 09:12 AM

I made it out last night just long enough to test the alignment. Luckily no stalling. The mount still has some odd noises moving from East to West but it doesn't sound harsh. The only problem I have at this point is accuracy. It is consistently off by about 30 arcminutes even after a 3 star align. GPS pulls coordinates and time is correct. I also use a polemaster so polar alignment is perfect. The good news is that there is zero backlash on this mount unlike the AVX. If I can just figure out how to improve the accuracy I'll finally be able to start imaging.

I use platesolving, anyway.  Many do. 

 

I clear the alignment data to avoid any problems, no longer do even a one star align.  GOTO the target, not caring if it's even in the frame.  Take a short image at high gain or ISO, binned if feasible.  Just need some stars.  Platesolve it with PlateSolve2, note where I'm pointing, correct.

 

Take another longer exposure.  Wham, there it is.  <smile>  Usually reposition some for esthetics.

 

Certainly faster and easier than a 3 star align.  I generally do only one target per night.

 

If you image one target over multiple nights, platesolving is definitely the way to go.

 

I presume you're no longer 3/4 turn out on DEC?   That would still be an issue.


Edited by bobzeq25, 17 April 2019 - 09:14 AM.

  • Dovakun likes this

#22 Dovakun

Dovakun

    Sputnik

  • -----
  • topic starter
  • Posts: 41
  • Joined: 16 Aug 2018

Posted 17 April 2019 - 10:36 AM

I use platesolving, anyway.  Many do. 

 

I clear the alignment data to avoid any problems, no longer do even a one star align.  GOTO the target, not caring if it's even in the frame.  Take a short image at high gain or ISO, binned if feasible.  Just need some stars.  Platesolve it with PlateSolve2, note where I'm pointing, correct.

 

Take another longer exposure.  Wham, there it is.  <smile>  Usually reposition some for esthetics.

 

Certainly faster and easier than a 3 star align.  I generally do only one target per night.

 

If you image one target over multiple nights, platesolving is definitely the way to go.

 

I presume you're no longer 3/4 turn out on DEC?   That would still be an issue.

Yeah, I was able to bring the DEC within 1/4 turn. I suspect my first night was balancing. I was trying to balance it like I would on the AVX mount. I watched a few videos and noticed that most people are balancing the RA and DEC with both gear switches disengaged and allow the whole system to float. That seemed to help alot. I will definitely do Platesolving for my long imaging sessions but I also plan on using this mount for visual imaging. I volunteer at the John Glenn Astronomy Park and will hit several objects in a night at 2-3min exposures. With this mount I'm hoping to get 5min on a few objects. I'm going to keep playing with it. Hopefully there isn't anything wrong with the gear alignment. It seems to return to zero just fine. 




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: astrophotography, equipment, mount



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics