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

CEM60 Mount Vibration

This topic has been archived. This means that you cannot reply to this topic.
62 replies to this topic

#51 tazer

tazer

    Surveyor 1

  • -----
  • Posts: 1,887
  • Joined: 22 Dec 2011

Posted 20 December 2014 - 09:16 AM

Adam,

 

I don't think there's any confusion on iOptron's part. I never received a replacement for my wonky CEM60, they never suggested I use a pier or anti-vibration pads (though I was using Celeston AV pads anyway), and my return process to OPT was started within the 30-day windows that OPT provides for such situations and it was processed within 45 days I believe. When they returned it to iOptron I don't know but I didn't have to pay a restocking fee. Just the $150+ shipping back to OPT which is fair.

 

Mark



#52 Footbag

Footbag

    Cosmos

  • *****
  • Posts: 9,115
  • Joined: 13 Apr 2009

Posted 20 December 2014 - 09:41 AM

Adam,

 

I don't think there's any confusion on iOptron's part. I never received a replacement for my wonky CEM60, they never suggested I use a pier or anti-vibration pads (though I was using Celeston AV pads anyway), and my return process to OPT was started within the 30-day windows that OPT provides for such situations and it was processed within 45 days I believe. When they returned it to iOptron I don't know but I didn't have to pay a restocking fee. Just the $150+ shipping back to OPT which is fair.

 

Mark

 

That's interesting.  Maybe iOptron should reach out to Mark's vendor and see what's going on.  

 

I'm a bit curious...  Is this dampening?  Or is this a matter of the gear mesh?  The two issues are complete different.  One could be from the tripod, one cannot.  



#53 WebFoot

WebFoot

    Surveyor 1

  • *****
  • topic starter
  • Posts: 1,687
  • Joined: 02 Jun 2005

Posted 20 December 2014 - 10:21 AM

 

Adam,

 

I don't think there's any confusion on iOptron's part. I never received a replacement for my wonky CEM60, they never suggested I use a pier or anti-vibration pads (though I was using Celeston AV pads anyway), and my return process to OPT was started within the 30-day windows that OPT provides for such situations and it was processed within 45 days I believe. When they returned it to iOptron I don't know but I didn't have to pay a restocking fee. Just the $150+ shipping back to OPT which is fair.

 

Mark

 

That's interesting.  Maybe iOptron should reach out to Mark's vendor and see what's going on.  

 

I'm a bit curious...  Is this dampening?  Or is this a matter of the gear mesh?  The two issues are complete different.  One could be from the tripod, one cannot.  

 

It's gear mesh.  I took the cover plate off, and you could see the play in the worm gear.  The only way to minimize the play in the gears was to tighten the clutch knob down so much that the motor would not work.



#54 GJJim

GJJim

    Skylab

  • *****
  • Posts: 4,024
  • Joined: 09 Sep 2006

Posted 20 December 2014 - 11:20 AM

Most worm mechanisms use a spring to set the gear mesh tension. My recollection of basic mechanics is that spring forces vary linearly (within limits) versus compression -- halving the length on a compression spring doubles the force. If iOptron is instead using the attractive force between magnets as a substitute for the spring, is this force linear versus the separation distance? A nonlinear force profile might explain the odd behavior of the mechanism when the adjustment knob is tightened.



#55 tazer

tazer

    Surveyor 1

  • -----
  • Posts: 1,887
  • Joined: 22 Dec 2011

Posted 20 December 2014 - 11:26 AM

I never removed the cover to be able to determine but it may have been a matter of gear mesh as it got better if I "overtightened" the engagement knob. Of course the motors would lock up when I'd do that so that wasn't a viable solution for me. I determined it wasn't tripod related as I could push the saddle with my index finger and see it move a significant amount. I understand seeing 1-2mm of play at the end of the CW bar in a normal mount is typical, but seeing more than that so near to the worm on an essentially backlash free design tells me something was wrong.

 

It's possible there was a sweet spot there somewhere but it would have been ridiculously small. Perhaps like 1/64 or 1/128 of a turn, or some amount that wasn't easily repeatable. Regardless, I never found it and while I'm not a mount expert I'm experienced enough to have better luck with a CG5 and a G11.

 

Mark



#56 rkayakr

rkayakr

    Surveyor 1

  • *****
  • Posts: 1,501
  • Joined: 27 Oct 2010

Posted 20 December 2014 - 11:33 AM

Most worm mechanisms use a spring to set the gear mesh tension. My recollection of basic mechanics is that spring forces vary linearly (within limits) versus compression -- halving the length on a compression spring doubles the force. If iOptron is instead using the attractive force between magnets as a substitute for the spring, is this force linear versus the separation distance? A nonlinear force profile might explain the odd behavior of the mechanism when the adjustment knob is tightened.


Correct - the force between two magnets varies as 1/separation^2 plus some correction terms for the magnets shape. The slope of the force (how much force change you get for a change in separation) is then ~1/separation^3. This would make the adjustment much more sensitive than a linear spring where the force varies as separation and the slope is a constant.

Edited by rkayakr, 20 December 2014 - 11:39 AM.


#57 orlyandico

orlyandico

    Cosmos

  • *****
  • Moderators
  • Posts: 9,595
  • Joined: 10 Aug 2009

Posted 20 December 2014 - 12:08 PM

Sounds like worm end float??! 



#58 tazer

tazer

    Surveyor 1

  • -----
  • Posts: 1,887
  • Joined: 22 Dec 2011

Posted 20 December 2014 - 12:52 PM

Hmm, that's a good observation orlyyandico. When I pressed back and forth on the RA axis I didn't necessarily feel a "clicking" like you'd expect from backlash, instead it seemed to "give" under slight pressure. I had assumed it was belt-related for this reason but worm end float may have been the culprit.

 

Mark



#59 Antonio Spinoza

Antonio Spinoza

    Surveyor 1

  • -----
  • Posts: 1,768
  • Joined: 07 Aug 2014

Posted 20 December 2014 - 12:53 PM

 

So, What your trying to get across is that all CEM60 mounts are junk because you had a problem. I just did a search and found many complaints about the G 11.

 

I had a CEM60 with similar issues as WebFoot's and a similar customer service experience. I have never claimed that all CEM60's are junk, rather they're new and have issues that need to be worked out. I went from a CEM60 to a G11 because I wanted something that would work right out of the box. iOptron felt the CEM60 was ready for the general public but mine definitely wasn't. I shouldn't have to spend months beta testing the mount at full price when members of the beta team got a substantial discount on their mounts.

 

 

Me, personally, whenever I buy something, I never read the positive reviews, only the negative ones.

 

Agreed. I knew my purchase of the CEM60 was a gamble as there was no history on the mount what-so-ever. I was prepared to return it if it didn't do exactly what it was advertised to do. I had researched the G11 and noticed that most of the negative reviews were about the Gemini II hand controller and were all a couple of years old. The mount design itself is well known (it hasn't changed much in 2 decades) and its few issues (e.g., backlash, 76s error, etc) were well discussed.

 

If I put weight in positive reviews I'd be picking up a CG5, a C11 and getting ready for 30-minute subs all night long with a 90% keeper rate...

 

 

I think it is fine as long as people are reporting facts--things actually happened.  I even believe that sharing facts (no matter positive or negative) should be strongly encouraged in our community.  No one should be blamed as long as what he/she shares are facts.  Then it is up to the readers to decide whether these are isolated cases or a general trend for that particular product.

 

There's a time and place to vent about vendors. If this thread is to retain value then venting shouldn't be done here (not that I think it has.) The issues WebFoot and I experienced are legitimate. They don't affect all CEM60's and, unfortunately, iOptron doesn't know the cause of the problem. My mount had stalling issues on top of the RA play. I would describe the RA play as being able to push against the RA axis and seeing the saddle move 5+ mm. It wasn't slack or backlash, as the worm was fully engaged. It felt more like a belt or something was flexing internally. Unfortunately my attempts at guiding yielded very poor results. Actually, my results seemed to indicated that guiding was essentially useless as I was getting close to 8" peak-to-peak of error which match the encoder printout that came with the mount. iOptron had me changing my guiding settings instead of addressing the RA play issue which I felt was the real culprit. Sadly, I never took any long duration (i.e., greater than 2-3 minutes) exposures without my stars being elongated even while guiding.

 

I wouldn't blame you if you wanted to point the finger at the user. Heck, even though I had been guiding my CG5 for a couple of years even I doubted myself. That doubt was quickly dispelled the first night out with my G11 though. After getting guiding going and having a PHD2 graph which looked like I expected it to (better in fact) I took a 5-minute exposure with great stars, then I took a 10-minute exposure again with great stars, and finally I took a 20-minute exposure yet again with great stars. And that's the experience I was looking for. A mount that just worked.

 

I'm sure iOptron will work through all the issues and have a reliable product at some point. In fact, I don't recall seeing many other reports of the RA play/vibration issue recently so perhaps they've already taken care of that problem. I do sincerely hope the CEM60 matures quickly which will provide another alternative for folks out there.

 

Mark

 

 

I had an experience similar to both of these.  Been through two CEM60s and have seen both the promise of the engineering design and (IMO) incompleteness of its productization.  In my opinion, the mount is not ready for widespread amateur use due to lack of consistency and QC in manufacturing, the ease with which it can be damaged, and the overstatement of its specifications.  That does not mean it cannot perform exceptionally when used properly.  I bought a new CEM60, paid full price and immediately had to replace it because it wouldn't track correctly at all (defective board).  Got a replacement and had fun with very accurate GoTo, but had trouble with RA play and had to futz with worm gear end cap.  Also, with <30 lbs it was very shaky no matter how tightened down everything was (on a 48" pier).  Finally measured PE through slow horizontal slewing across camera frame and found it to be much higher than advertised (+-15 arcsec or so) and I was never able to get tracking and guiding as smooth as I expected.  Moreover, tracking and guiding were exceedingly dependent on weight balancing and I had to use weight velcroed to to the side of my OTA to carefully adjust the weight symmetry on the OTA itself in order to be slightly east-heavy, and then readjust weights after meridian flipping.  iOptron refused to take back the second mount (past 30 days, but my opinion was that it did perform as advertised), but I traded it back through OPT at a slight and reasonable loss and bought an AP Mach1.  iOptron claims the worm gear was damaged through user error to explain tracking problems but they still fixed it so it could be resold, so I give them credit for that as well as their customer support which was very good when I had questions.  I understood the magnetic gear engagement mechanism as well as requirements for transport of the mount, and I could not prove that I did not personally damage the gear despite having done nothing obvious to do so.  I have not had a single problem with the Mach1.  It has behaved flawlessly since the first time I turned it on and is phenomenally easy to use.  It is rock solid on a 42" pier, does not have problems with play in either gear, and tracks and guides nicely without undue need for precisely fine-tuned empirical parameters.  If a little play does build up, it's loosen 2 set screws, gentle tap, retighten set screws and it's rock solid again. 



#60 Antonio Spinoza

Antonio Spinoza

    Surveyor 1

  • -----
  • Posts: 1,768
  • Joined: 07 Aug 2014

Posted 20 December 2014 - 01:00 PM

Hmm, that's a good observation orlyyandico. When I pressed back and forth on the RA axis I didn't necessarily feel a "clicking" like you'd expect from backlash, instead it seemed to "give" under slight pressure. I had assumed it was belt-related for this reason but worm end float may have been the culprit.

 

Mark

 

I had to tighten the worm end cap to reduce RA play on one of my CEM60 mounts, as you are both suggesting.



#61 tazer

tazer

    Surveyor 1

  • -----
  • Posts: 1,887
  • Joined: 22 Dec 2011

Posted 20 December 2014 - 01:08 PM

Antonio,

 

That was my other gripe with the CEM60. The manual states numerous times that the worm is only warranted due to non-user damage with no clear explanation of how that determination would be made. When I received my CEM60 the RA was partially engaged. This was a mount that shipped straight from iOptron and they were explicit that it should be completely disengaged after putting it in the case as worm damage may occur. I followed the instructions to tighten it before removing it from the case but that didn't prove successful. Unfortunately the engagement knob itself wobbles so if it's not completely orthagonal to the worm it will appear to tighten when in fact it doesn't. Also unfortunately, there's not enough room in the case to put your finger in and get it orthagonal to tighten it properly, there's no cutout or anything and my fingers aren't overly large. This is a design oversight IMO and if you're not cautious then entire RA assembly will flop over with full force and if your gears are partially engaged the tops of the teeth will hit one another when it does causing who knows what damage.

 

I was honestly glad that my mount had a reproducible problem as I felt the work engagement/disengagement process for storage/travel was something that would end up causing damage over time. One wrong move and your worm wheel or ring gear is damaged requiring non-warranty replacement... No thanks. I prefer a clutched design like my CG5 or G11.

 

Mark


Edited by tazer, 20 December 2014 - 01:09 PM.


#62 Antonio Spinoza

Antonio Spinoza

    Surveyor 1

  • -----
  • Posts: 1,768
  • Joined: 07 Aug 2014

Posted 20 December 2014 - 01:20 PM

I agree on this point tazer, especially given that my second CEM60 did come with the gears fully disengaged as it was supposed to (I was there to pick it up and saw it first opened to check out).   Given the problems with getting your fingers into the case to engage / disengage the gears, I checked multiple times every time I put it in or took it out of the case for both gears and it never slipped taking it out of or putting it into the case.  The only thing I can think of that could possibly have led to any damage would be disengaging and re-engaging the RA gear for OTA balancing.  When disengaged, the RA axis floats nearly friction free, and when you go to re-engage the gear, it sometimes lines up with teeth on top each other.  There is a slight slip and clunk when the gears find each other correctly and engage.  I couldn't imagine the gear being soft enough for that slight scraping to damage it though.  When iOptron showed a picture of the damage, it looked like gears had been scraped across their tops however.  The gear mechanism does appear to be a little overly open to damage and rather than engineering a mechanism to reduce the risk of gear damage, they appear to have engineered a mechanism to encourage it, then state clearly it's not covered by their warranty (that said, they still warrantied it). 



#63 vdb

vdb

    Surveyor 1

  • -----
  • Posts: 1,531
  • Joined: 08 Dec 2009

Posted 21 December 2014 - 01:10 PM

The engage/dis engage thing is bad design, it is an accident not if but when it happens, I do understand why they designed it that way. But in real world, and especially a portable setup, an I believe this mount is especially geard towards portability, it will lead to accidents and damages to the drive train ...

 

/Yves




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






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics