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I have been wondering for those with really excessive reported backlash about Dec gear mesh being too tight and causing sticktion, where the gears is literally sticking and just does not move for small guide inputs, they may not generate enough torque to overcome the initial friction and get the axis to actually move. I know that I have seen people report iOptron support suggesting tightening OR loosening the mesh to resolve RA backlash. One of these nights I really should mount the C925 on mine (Bigger and heavier than the little SVX80T I usually have on it) and spend a night fiddling with the Dec mesh, starting with it obviously too loose and slowly working my way in to see where PHD reported backlash stops improving. |
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Well I finally heard back from iOptron, this was their reply: “1. Since You mentioned there is 4 sec backlash, I would suggest to confirm it with set the DEC slew speed at 1X. Aim the scope on a star or distant object, press UP key then DOWN key, you should see the star or object moving after 4 sec. This is highly unlikely. I suggest this too before: 2. Change the DEC guiding rate setting to a large number 3. Release DEC belt tension a little bit. It should be straight forward (see attached). 4. Adjust the meshing following instruction at the end of the full manual” I will try their suggestions the next clear night. Interesting that they say to try loosening the belt. Fingers crossed! |
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I have actually just run in to my first real issue, but it seems to be a Windows problem. The imaging PC insisted on doing an update last night so I ran that before connecting the gear, but then the iguider refused to connect and was showing as a failed USB device in device manager. Plugging the USB cable to the mount in to my laptop instead, the iguider camera showed up in the cameras section of device manager like it should. I might have to see if I can roll back the update done yesterday, I managed to get it connected and it stayed that way for the night but when I tried disconnecting and reconnecting it this morning it failed again. I have clear skies for the next couple of days so I really don't want to miss them, the weather has kept me from imaging for about six weeks! |
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I would experiment a bit first, if you have not, turning off power to both reconnecting, maybe use one of the USB info tools (e.g. usbdeview from nirsoft is good, and free). Windows will eventually force the update. It sounds a bit odd that the windows update directly makes it fail, it seems more likely that something caused something which caused something which threw it off. Try a different port perhaps on the computer. I'm not saying it couldn't be windows update -- they cause a LOT of issues. Just that sadly the path is usually through not back. |
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Through, not back is my concern. I power cycled everything several times, including cold booting the PC and power cycling the mount together, disconnect/reconnect etc, disconnected all other devices to connect to the iguider and mount alone (At the moment I have camera, filter wheel and focuser connected via the USB hub on the 70) I might have to give usb-deview a try to see if it shed any light. The only thing I am not sure I did was change USB ports on the PC. It is in a plastic enclosure and I have bought three ports to the outside in weatherproof connectors. I can try that during the day today. But everything is normally connected via the one USB3 cable and everything else was working properly at the time. The only thing that had changed since the guider last worked properly was the windoze update. I did a dry run a few days ago after adding a filter wheel in to my image train (I am in the process of going from an OSC ASI2600 to a mono one) and everything connected and worked then. I had changed to the iguider ASCOM driver to get away from the irritating need to set the camera up manually every time, and that worked perfectly during the dry run, shooting a dark library and behaving otherwise as expected when the cap was removed from the guider. |
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Windows caches information about specific connection context. That's why some devices that simulate COM ports get different numbers, it only takes a very minor change to create a new context. USBDeview will show all the unused contexts from past connections as well as what's connected now. I mention it because getting on a different port that is slightly different (not just a port on the same hub) may make it re-initialize its context. Most mini-PC's have more than one type of port (even if just 3.0 vs 3.1) so sometimes that gives you a choice. There's no good reason why a change of such context will cause a problem; I'm not suggesting that. But windows is still at heart the same system that back in the day the first thing you did when something went wrong is reboot - bug filled and a bit flakey. So sometimes you just change things up and avoid a bug. It's kind of scary on an older computer to see how many USB past connection contexts it remembers.  |
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I am following this with attention. Your USB problem looks like the issues i have since the start with my 70G, impossible to stay with everything connected more than 3 to 10 mins depending on the software configuration. I am in conbatct with iOptron, they suspect a power issue, so i will do some tests based on their request, connecting each equipment one at a time on the hub. Let's see... here its strange that it happens just after a windows update. but i agree with Linwood, not sure its directly linked to the update, it could have revealed something else. I also have usbdeview, i see huge lot of infos but i am fully unable to do something with all these infos... if there was some tuto somewhere explaining a bit what we can do with all these infos... would be nice... |
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well, I have usually stuck with the same port (As I wrote above, a one cable connection on this one) so my first test might be to change ports I will have to dig in to confirm but I do not believe the external USB ports on an Gen 10 NUC are on a common hub. The frustrating thing is I am working from home today, but if I want to be allowed to keep doing that I better not go skiving off to play with astro stuff in work time. Posting here in breaks is bad enough. |
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Changed ports (Two USB3 ports are presented outside the case on this one) and up she came. I am Irritated that I did not do that last night but along with the normal advice given to people doing AP, I had taken to ensuring I always used the same ports. USBdeview showed the failed connection so I uninstalled that and rebooted the machine and it is still behaving. I am glad it was that and not something broken by the windows update (Or at least if it was broken by the update, resolved like this) as that could have been a lot less tractable an issue to fix. |
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Glad that u solved ur issue. For me, i wanted to do test requested by Ioptron, so first i did a test during daylight with everything connected to the USB hub of the mount, launched everything, both cams taking series of images, mount moving fastest speed, focuser too, and.... Everything was working fine !! No crashes, no disconnections at all... I don't understand... Need to test again in night time. |
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Hello All, Here is my experience with the DEC backlash of my CEM 70 and how I fixed it. While using PHD2 the graph clearly showed the backlash issue. The graph was going up and down so I decided to take measures. I used PHD2 backlash measurement and the tool reported about 2400 ms. Then I tried to see whether this is real. I slew to the moon (a star will do as well) and checked the responsiveness of the hand control. Yes, the backlash of 2 seconds was real. Both iOptron and FLO suggested to check the tension of the belt of the DEC motor. iOptron even sent the instructions for the CEM120. So I decided to act - took the DEC motor cap off. Then I could clearly see that it took time to transfer the movement of the motor to the mesh. There are three screws which hold the motor in place. I loosened them a bit, held the motor down and tightened the screws. I checked again and now the movement of the motor was directly transferred to the mesh. Checked the tension of the belt - everything was ok - the belt was not too tight and could still flex. Next step - adjust the mesh through the adjustment screws. I saw that if I tightened too much then the backlash even increased to 4000 ms. The best way to do this adjustment is to be with the hand controller in hand, make adjustments and test. In this way I found the place where pressing a key on the remote directly transferred to movement on the screen. So with these two procedures - adjusting the tension of the DEC belt as well as adjusting the gear mesh - I managed to make the DEC of my CEM70 quite responsive. Used PHD2 to measure - the DEC backlash decreased from over 2400 ms to about 300 ms. Now I check the automatic DEC backlash compensation figures in PHD2 and they remain fixed to about 300 ms or several ms less. The PHD2 graph does not show DEC backlash as well. Looking back at the procedure that I performed - It is quite easy and now I even have more knowledge on how my mount works. I love MY CEM70 mount. Here is how my guiding was going in one of my latest sessions from March:  Best regards, Sektor |
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The usb issues described above sound exactly like what I went through. From the very beginning (November) I had problems.
Once I got everything working, it worked great, but was very frustrating doing that every night. Emailed iOptron almost immediately, but took a month to get the first response after I asked the vendor to step. Then there was a month of back and forth emails asking me to pull out the boards and press on various things, as well as checking the cabling. Their responses always took 1-2 weeks. They finally agreed to let me return the mount for repairs at the beginning of February. I just got the mount back last week and tried it for the first time last night. I was able to use both USB ports on my computer. Everything just connected as it should. Was a much more pleasant experience. I just wish I hadn't had to pay shipping both ways for the repair... |
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uhhh, i hope i will not have to return my scope... there could be huge talks for that, i am in France and don't know what we could do with shipping costs |
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Unfortunately I spoke to soon. The iguider cam disconnects after a period and it takes a reboot to temporarily get it reconnected. I lost the whole night last night. I even reseated the connector on the guide cam board. Everything else is working properly. Today I am going to try hooking the other imaging PC up to it (I have two imaging rigs) and see if it looses the cam as well. With shipping time and cost, and repair time, there is no way on earth I am sending it back. I will buy an ASI290MM and fit an OAG before that. Edit, I plugged it in to the other imaging PC and the iguider camera is showing up as an "Unknown device" so unless my first thought about a windows update related issue was on the money (Both imaging PC's are at the same update level) I am stuck, with what looked like another promising night weather wise tonight, finished before it started. I have not had a chance to look, is the actual USB hub down in the base of the mount and is this cabled down to there? If I can get at it I will try reseating the connector at the hub end. Edited again. I slid out the main board and reseated the connectors on the USB hub, no change. Looks like he's dead, Jim. |
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Well, nothing else to lose so I have tried rolling back the most recent windows update. The cam was dead before and popped straight back up as a camera in device manager when it rebooted after rolling the update back. I have had PHD2 running looping exposures for 20 minutes now without issue. I will cover things up and leave it doing that all day to see if it stays connected. Quite annoying to miss out on what was a rare night of good weather, hopefully I get at least a few good hours tonight between the clouds. Hard to know what to expect as recently the forecasts have been changing radically over the course of an afternoon. |
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Maybe it only works when there are clouds or daylight.  It will be interesting to know if it continues to work well without the update. It would be more interesting to update again and see what happens but I think everyone will understand if you don't rush into that. |
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It is still looping away. Tonight looks like it might give me some imaging time so if it keeps working I will leave it as is. If it does keep working and I can image tonight, and the clouds close in after that as expected then I will update it again and see if it breaks. |
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| Are u using the ascom driver ? |
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| Both yes and no. I had it installed but the night before last was the first time I was using it. If the camera connection fails and it shows in device manager as an unsupported device, then the ASCOM driver fails to connect too. |
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ah ok, i was using it and it was working fine, better than without driver, at least we can manage the iguider from other tools than PHD, and also PHD can change the exposure itself, no need to go in the camera to change values... tonight i tried again my connections, if i connect on the mount hub, everything is collapsing, crashes, diconnections, etc... if i connect 533 and 224 together and directly to a powered switch then to the PC, without going through the mount, it works perfectly. but strangely, this afternoon everything was working through the mount, and not tonight. The cold ? anyway i think that i will have to route an USB through the mount head in order to connect cams directly out of the mount. |
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| I rolled back and then re applied the updates today. I had to go out to work so I left it running looping exposures, it was still going 6 hours later when I got back so that is promising. |
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Hi all, Here is my experience summary with the CEM70G of the last 3 months ; Overall I'm quite happy with the mount despite consistent issues and glitches. - The Con's; The guiding quality with my 910,f/7 and OAG are below my expectations and the intrinsic Periodic error is more than double from iOptron specification +-3.5". Guiding is very inconsistent in both RA and DEC, although the DEC guiding is mostly very good but at times can be very spiky with no apparent reason(seeing isn't the problem). I had to adjust RA guiding settings almost every session even on consecutive similar nights. It seems the mount can handle very fast corrections and at some points I even set Min Movement to 0.05. Guiding errors range 0.5"-0.8", sounds ok but as I said, below my expectations for this mount, with my AZEQ6 I used to always 0.5" and below. I'm still hoping to find regular setting to avoid changing each session. - The Pro's The mount is very solid, steady and easy to carry as it is with the Tri pier. I found a way to carry the Tri pier without the need to retract the pier so I never need to loosen or tighten the 6 annoying screws every time I fold it. Good cabling management, USB hub functions reliably. iGuider: I used the iGuider with my small OTA (480mm f/6) and guiding errors were adequate, mostly around 0.6" in contrast to the above. The initial focusing is awkward but once I achieve focus I never needed to adjust. iPolar: Quick and easy method to polar align, accuracy depends on setting the iPolar camera center of rotation precisely. Commander: As Paul mentions in his comments, I have similar problems with the mount connection and settings, particularly when changing imaging locations. The mount Park coordinates is reset occasionally and the time zone too, this all means user needs to enter the park coordinates manually again and Sync with the PC (simple enough but still no reason for this to happen). I've learned to always check before I begin the session. I run the commander and check/adjust the settings before running Voyager, this fixes the problems for the whole session. Score: 6/10 |
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What I am taking away from these reports is basically that the CEM70 is not ready for prime time and needs another design pass. Which is a damn shame since it would really be a fantastic upgrade from my aging EQ6. And there isn't really an alternative in the same price and load-capacity range... I was hoping Skywatcher would eventually release their CQ350 (announced way way back...), but doesn't look like that will happen  |
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Hi, I want to add my two cents to this: I have the CEM40 mount and can achieve constant 0.4" RMS for guiding on the CEM 40. I don't use any PEC correction or whatsoever. The most beneficial setting is to use multi-star guiding in PHD2 as this minimizes the effect of seeing enormously. I typically use exposure times of 2.5 seconds. The mount is used with an f=360mm refractor an a f=1550mm SCT, both with guide scope. There shouldn't be any worm backlash as the worm is spring loaded. Björn |
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The mount is used with an f=360mm refractor an a f=1550mm SCT, both with guide scope. There will inevitably be a small amount of backlash, most of it on either axis is in the belt drive component. The RA backlash should be largely irrelevant, it may impact goto accuracy slightly but should make very minimal impact on guiding if any, it never reverses while guiding and the spring loaded worm should control most movement due to wind gusts or similar. What does need a little time to fettle is the tension adjustment of the worm, the last time I imaged I noticed the occasional moment where the RA would have one quick oscillation then settle down again, there was no matching wobble in Dec so I doubt it was a wind gust. I suspect the worm was a touch too tight and any imperfections in the worm or the ring gear or a bit of contaminant in the grease was making a momentary "tight" spot. I really need to spend a night with it with all the gear bolted up as if I am imaging, but working to get the gear tension right and play with guiding settings rather than image. The problem is that imaging nights have been so rare that I have not been willing to burn one by using it to fiddle instead. |
