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CEM120EC2 - Looking for Help and Information

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45 replies to this topic

#26 rgsalinger

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Posted 24 July 2019 - 05:38 PM

I don't want to digress too far from my original request to hear from other owners but here are some answers----

 

1. The two crops shown are different because I rotated the camera 90 degrees. In both cases the elongation is parallel to the RA axis. 

 

2. The pier rests on a 48x48" block of concrete/rebar isolated from the rest of the observatory. I sit in a separate room. The wind was zero (I have my own weather station.)The stars were round with my Tv127 only two weeks ago. I have even lowered the pier by about 6" for better stability. So, while nothing is proven vibration would be a real long shot.

 

3. The scope worked well on the Paramount previously - no elongated stars with good guiding. Anyone can get oblong stars with bad guiding, getting them with excellent guiding takes some underlying issue and with the OAG bolted directly to the integrated camera I'm ruling that out. 

 

4. I can't take rapid cadence main camera exposures and the guide camera seems to have round stars due to the image scale being 4x larger (smaller?). The jitter is a fixed value like .4 arc seconds I'm betting so it only shows at fine image scales. .

 

I was able to speak briefly to the head of sales at iOptron today. I got the same kind of hand waving from him about the problem. He did say that he was aware of a problem with these mounts and that they are "working on it". Given that the mount is 15 months old, and they have known about the problem for at least a year (reasonable guess) it's unlikely that they can suddenly solve it. They have a bad design and "working on it" this long doesn't bode well for getting it fixed.

 

You know I can't understand how they can still be advertising and selling a product that they know doesn't meet it's specs. Moreover they've been doing it for maybe a year or more. People save money for a long time to buy equipment like this. iOptron has always treated me fairly - this is my third mount from them. So this behavior has me baffled.

 

Anyway, I'd really like to hear from others who have the mount and do or do not have what appears to be an SDE problem. 


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#27 OzAndrewJ

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Posted 24 July 2019 - 06:09 PM

Gday Ross

As per a prev thread by Ross W

He had an SDE error of 1.5-1.8 arcsec per sec. Not sure if his mount is back from repair yet.

I also saw data from another user that showed a small peak at the SDE freq, but it was only registering at about 0.1 arcsec pk-pk, ie well withing the baseic noise.

 

Andrew Johansen Melbourne Australia



#28 OzAndrewJ

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Posted 24 July 2019 - 06:54 PM

Gday Ross

Just another thought

I can't take rapid cadence main camera exposures and the guide camera seems to have round stars due to the image scale being 4x larger (smaller?). The jitter is a fixed value like .4 arc seconds I'm betting so it only shows at fine image scales. .

Can you run the guider unbinned????

If so, maybe try grabbing some HiFreq unguided data via that. ( It cant hurt )

I just looked up my notes and the 120EC appears to have a 48:24 belt drive reduction.

The SDE freq is 72x fundamental and belt misadjustment would show at 48x

If you can get data that indicates a signal at either of these it may point a bit more to the cause

ie maybe during the move, the belt adjustment has changed????

 

Andrew Johansen Melbourne Australia



#29 rgsalinger

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Posted 24 July 2019 - 06:57 PM

I think that in my garbled communications with iOptron there was some allusion to having someone's mount in for repair. They have not offered me that option. I suspect that they think that they will get some working firmware and use his as a guinea pig (guinea mount?). Maybe they'll offer the same to me. I have to tell you that the mount is otherwise just terrific. Without any pointing model at all running at 2550mm it hit every target I went to on Saturday night. None of my other mounts ever did that. Even the Paramount needs the all sky solve for the first slew. (Standard with TPoint.) 

 

I just rejiggered the weights so that I now have more weight on it but higher up - as far as possible - on the counterweight shaft. Skies do not look promising at this point for a run. I have the beta firmware ready to load as well.

 

The mount has not been moved. The telescope was moved and put on the mount. Then the system was balanced, the various components hooked up and I began configuration. That took some doing as the computer had never run the planewave system, the Lodestar X2, or the QHY 16200A on it.

 

I can try the guide camera un-binned but it has an interlaced readout which may affect any results. If the new firmware doesn't work and iOptron has nothing more for me I'll put my ASI071 on it over the weekend and then I can get high cadence images. 

 

Rgrds-Ros



#30 spokeshave

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Posted 25 July 2019 - 08:40 AM

Anyway, I'd really like to hear from others who have the mount and do or do not have what appears to be an SDE problem. 

I doubt that it is SDE. If it were, it would be present in every mount. I have my CEM120EC permanently mounted in my observatory. It swings an EdgeHD 14 and Tak FSQ106 side-by-side, with a total payload of around 90 lbs, with 5 counterweights. I regularly image at 3910mm with the Edge, and I have not seen the eggy stars that you see. I have also collected high frame-rate video at 3910mm and see no evidence of any oscillation. 

 

Having said that, I think there are others who do see a high-frequency oscillation in RA - typically a small fraction of an arc-second in amplitude. I have seen video that shows the oscillation and am fairly convinced that it is ringing in the PID controller for the encoder. My guess is that the firmware uses a default proportional gain for the encoder controller that worked for iOptron in testing but can induce a feedback oscillation in some circumstances. If that's the case, it is something that should be correctable in firmware. I understand that there is a beta firmware being distributed that is intended to do just that. 

 

Tim


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#31 rgsalinger

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Posted 25 July 2019 - 06:27 PM

Thanks Tim for this.

 

Still zero from iOptron about any resolution to my problem or even a status report. If there was a way of turning off the encoders, then I could at least try to make some progress in fixing it. I guess all I can do is put it in its box and wait for something to come down the pike. It's impractical to sue them from 3000 miles away but they certainly are in breach of their warranty by refusing to repair or replace it. 

 

I had hoped that there were a bunch of folks out there who shared the same issue but there have been no responses at all. I guess if I bought boat then I could use the CEM120EC2 as an anchor. 

 

Rgrds-Ross


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#32 RaulTheRat

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Posted 25 July 2019 - 07:01 PM

Worrying indeed and terrible customer service. I hope you get a resolution at some point and hopefully sooner rather than later.

#33 rgsalinger

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Posted 25 July 2019 - 08:06 PM

Well, looks like I'm on my own here so there's no point in even discussing what the service level is. As I said, I'm looking for suggestions to identify user error here. I'm looking for people who have the same mount loaded with more than 50 pounds who can get round stars.

 

Right now I'm planning to try three things:

 

1. I did a complete tightening using wrenches yesterday so I'll run my test cases again. The strangest thing about the test cases was the unguided imaging crapped out at less than 2 minutes!

2. I have a beta firmware release that I can try and see if that at least improves things.

3. I will put a different camera on the system so that I can take the fast cadence images that were recommended to identify any SDE.

 

Maybe help the vendor understand the problem better if I can get them to even look at what I send them. If they don't work and there's no relief for me I'm just getting rid of it. There are too many mounts out there that will take this kind of load. 

 

Rgrds-Ross



#34 EFT

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Posted 25 July 2019 - 08:18 PM

You probably know this, but only make one change at a time starting with the adjustments you made yesterday.  That way will help you better identify the specific source or the problem, or at least what it isn't.



#35 rgsalinger

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Posted 25 July 2019 - 08:52 PM

Yes. Baby steps. Given what Tim said, just moving the weights around and making extra certain that everything is tight might change things and eliminate the problem. I can't get my head around why a change in focal length or weight would cause oblong stars at short exposures. I get that at some point the moment arm of the system exceeds the ability of the motors to accelerate quickly and smoothly. I also get that, at some point, the sheer mass of stuff on the mount exceeds its ability to remain rigid. That's not what's happening here. Both of those problems will show up in the guiding results but what I've got doesn't. 

Rgrds-Ross



#36 zliang

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Posted 26 July 2019 - 06:04 PM

If there was a way of turning off the encoders, then I could at least try to make some progress in fixing it.

Not sure if the motor control board is compatible with the standard CEM120, perhaps you can try flash the firmware of the NON-EC cem120, it should ignore the encoder and only responds to guiding command.

I must admit I have zero experience with ioptron mount, it's better to verify this with ioptron, just to make sure it won't void warranty and cause any damage.
 



#37 rgsalinger

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Posted 26 July 2019 - 06:15 PM

Others have posted that the firmware is the same for all models. What's actually different is the board itself. There's a jumper that you can solder/unsolder to make it think it's non EC. That's been tried but caused other problems. Interestingly when the jumper was soldered (meaning a non EC board) it uncovered extra features in the hand controller. Specifically suddenly PEC became available. Of course PEC makes no sense with high resolution encoders because the do the same thing, just do it better. 

 

iOptron keeps saying that they have a fix in the works but they can't test it due to weather. I keep offering to test it as I have clear skies since apparently Nanjing is sacked in for the summer. I suspect that having just one set of firmware may be hurting getting a fix out. I just wish that they would actually contact people who have the problem and give them a real status rather than hand wave "we're working on it". 

 

Rgrds-Ross



#38 rgsalinger

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Posted 28 July 2019 - 05:28 PM

Latest status. Received a beta release from 06102019. This was completely unstable. Would neither guide nor track properly. Ran away. Received a second beta release 06242019 was a bit better. Using aggression of 130 percent was able to guide at .7 arc seconds of RMS error. (Clean calibrations at DEC zero in both the SKYX and MaximDL.) Always oblong stars no mater guide/no guide or long/short exposures. 

 

Mount has been meticulously polar aligned, all nuts / bolts checked and carefully balanced. Seeing was excellent - scope showed oblong stars under 2 arc seconds after a focus run. I've asked to beta test anything that they can come up with. Their response is that they are waiting for the skies to clear (in China - Nanjing?) so that they can test themselves. 

 

Rgrds-Ross



#39 rgsalinger

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Posted 30 July 2019 - 08:11 PM

I removed my camera and put on a much lighter configuration. That allowed me to remove one of the 10kg weights (and move the remaining ones down a bit) as well as move my tube weights closer to the center of the tube. 

 

I was also able to run my guiding at .5 seconds of cadence and that showed a sawtooth of around .5 arc seconds. Did nothing for the images but there was no wild instability which I had seen several months ago running at a 1 second cadence. 

 

My next step is to remove even more weight from the system - there's a 3 pound dovetail on top and I think I can also get rid of one of my 2 three pound tube weights. Then I'll see if, on a good night, I can at least get close to round stars.

 

Nothing further from the vendor, I suspect that they are just ignoring the problem as there don't seem to be many other people who are having. it. So, if that's the case, it may well be that it can be fixed somehow.

 

Rgrds-Ross



#40 rgsalinger

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Posted 18 September 2019 - 09:56 PM

I eventually moved the camera and the entire system over to my other mount, a Paramount MX+ which is about 10 feet away in the observatory. For various reasons - all user errors - it took a few nights to get the system up and running. Immediately I noticed that exact same problem - oblong stars. At the same time the CEM102EC2 which now have my TV127is on it was working flawlessly. Hmm. I spent several nights trying to figure out why the Paramount was giving me trouble. Then the light went on and I realized that it was essentially the same exact problem that I had using the CEM120EC2. That led me to realize that the only thing that they had in common were the telescope and the camera. I checked the telescope and the collimation appeared to be essentially perfect. I suspect that the filters/filter wheel might be the problem. I removed all of the filters and still had oblong stars. I tried two different sets of attachments to fit the camera to the telescope. That did nothing. I tightened up the screws that hold the focuser to the backplate. That still left me with oblong stars. Finally, in desperation I stopped the QHY16200A's fan from running and I got perfect stars. I then changed cameras and got perfect stars. So, I sent the camera in for repair. I can only speculate that the fan was causing the entire system to vibrate. We'll see when it comes back. Anyway, I don't think that this is actually a CEM120EC2 problem at this point. I won't know for sure until I have the opportunity to move the big scope back to the mount. Just wanted to post an update.

Rgrds-Ross


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#41 EFT

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Posted 18 September 2019 - 11:48 PM

Camera fans (actually any fans) can provide enough vibration to cause trouble if they get off-balance (e.g., from bearing wear or defect).  The fans used for cameras, small computers and other things that might be placed on a telescope and mount are all fairly high RPM to make up for their small size but they have to be very well balanced or they can vibrate like crazy.  For vent assemblies I use what are called "vapo bearing" fans which essentially levitate the blade assembly to avoid the vibration that you can see much more commonly with ball bearing fans.  With some of the larger cameras that have two or more larger fans, it is certainly something to keep in mind.  Just one more thing to watch for.



#42 rgsalinger

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Posted 19 September 2019 - 12:20 AM

I'll look up vapo bearing fans if the camera returns with the same problem.

 

I have some hope that this is the problem. Just as I was setting up the system -- it moved from New Mexico to my new (almost finished) observatory in July - I was having trouble getting the camera to work. It was late and dark and I was tired. I thought that one of the screws that holds the filters to the carousel was too long and the system was sticking. I'd had this problem when I set up the camera two years ago but had not seen it since.

 

When I went out to look at the camera the fan was not moving. I changed power points but the fan would not start. I thought that the camera was simply broken and packed it up and brought it home. The next morning I figured I'd take it apart and see what was doing. At that point I noticed that a huge moth (not making this up) had gotten into the fan housing and that's what stopped the fan! I cleaned everything out with my tiny vacuum cleaner. After that the problems began.  I really was not thinking about the fan until I found it was the problem So, that fan was probably running for 30 minutes or more in a stalled condition.

 

We'll just have to see what's what. It's a standard 80x80 fan so I'm sure I can find something better if needed. 

 

Rgrds-Ross



#43 atalas

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Posted 19 September 2019 - 12:22 AM

Sorry to read abut your problems with this mount Ross...you have had great results from It in the pass.

 

I've read a lot of the post here but not all so forgive me If I've repeating something that's been addressed by you or others.

 

I have a question:

 

Have you had the main mirror out of the CDK for cleaning? I ask because looking at the stars in your pic It sure does remind me of when I had slight pinching of the main mirror on an RC12...and of cause the fact that a 3 second exposure is elongate as well.

 

Anyway I"m sure you'll solve the problem sooner or later Ross....best of luck mate.



#44 rgsalinger

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Posted 19 September 2019 - 12:31 AM

No. I had it cleaned at PlaneWave about 18 months ago. I checked the collimation with one of my imaging partners and we agreed that it was perfect (or close to). Once I changed the camera here's what the stars looked like  in the upper left hand corner

 

Capture.JPG


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#45 EFT

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Posted 19 September 2019 - 03:23 AM

The next morning I figured I'd take it apart and see what was doing. At that point I noticed that a huge moth (not making this up) had gotten into the fan housing and that's what stopped the fan! I cleaned everything out with my tiny vacuum cleaner. After that the problems began.  I really was not thinking about the fan until I found it was the problem So, that fan was probably running for 30 minutes or more in a stalled condition.

I REALLY hate finding bugs in equipment.  The thing undoubted fried fan, hopefully that's all.

 

The fans I used are from Sunon and are called "vapo bearing" or "mag lev."  I haven't used anything larger than 25mm so I'm not sure how big they go on those. 



#46 atalas

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Posted 19 September 2019 - 08:22 AM

Ah missed your camera fan post....good sounds like you found the cause waytogo.gif 




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