ioptron CEM70G initial impressions

[The_bluester]

So, after a couple of months wait due to both COVID impacts on production around the world, shipping delays worldwide and the frenzy of sales that COVID seems to have induced on astro gear, I received my new CEM70G a couple of days ago. Time for some initial thoughts.

Firstly, the mount comes well packed, it is in a lined aluminium case and the case itself is double boxed for shipping. The only potential trip up I can see is that the supplied counterweight ships in a separate box (Presumably for shipping weight reasons) which is an opportunity for it to get separated in the shipping process.

My initial impressions of the mount are good, basically the whole thing seems to be comprised of stainless steel and die cast or milled aluminium, everything you can touch feels nice and solid. The gear switches are positive to operate and when they are released the mount moves very smoothly and freely for balancing. It moves so much more freely that the Atlas (AZEQ6 clone) even in Dec (Which is the easier axis to balance on the Atlas) that as soon as I mounted my scope I can see I really need to relocate my focus motor if I want it to balance properly. It sits out to one side and makes proper dec balance more or less impossible, which I never really picked up on the Atlas.

Size wise it is a bit of a beast coming from an AZEQ6 type mount. The only (Not really negative, just ambivalent) build quality note is about where the threaded cap for the polar scope is screwed in to. It screws into the cast alloy elbow that connects RA shaft to the counterweight bar and the thread there is cut after the part is coated so it stands out as the only bit of raw aluminium in sight. Bit of a first world problem if that is the worst I can find. It is only visible when you are using the electronic polar scope, the rest of the time that plug serves as a lens cap. Visually it looks a little strange when I have been using a GEM until now, it looks like the counterweight is pushed way, way out in front of everything but that is just because on a GEM the telescope would be right on top of the counterweight and on these it is sitting back between the bearings.

With the commander software loaded it connected straight up to my imaging PC. The ability to find it's own home position from any location is a great function to start it off, the guide cam and polar cam connected straight away, connection to my imaging software (Voyager) was as simple as selecting it, after homing itself, goto commands on the bench resulted in it going more or less where I expected. The GPS module connected up and set the time and location from inside the house, but not from inside my garage (It was near a window in the house and under foil backed insulation in the garage which probably blocked the GPS signals)

A quick dummy mount of my gear in the garage and connections with whatever cables I had available say everything seems to work via the USB3 hub and power connections, better still, even on my converted Celestron tripod, crashing the camera is not possible. No matter where the scope is pointed the RA hard stops limit travel so that the camera has maybe 20mm clearance to a tripod leg at worst, it will be even better on a pier. If I mess up the alignment of the electronics badly enough to run it into the hard stops I might mechanically damage the mount but the camera and telescope will be protected, not a bad trade given that they combined are still worth more than the mount is.

The only thing that will need watching is that care is needed in the order things are set up after pulling it out of the case. it should be in the case with the gear switches released and the RA axis is locked by the allan key provided to mount it on the tripod. It comes to a point where you need to pull that key out of the axis locking hole to do up the socket screws (Captive ones) that bolt the mount down on the tripod or pier, and if you forget to engage the RA gear switch first you will have a bit of a nasty time! On the CEM60 I believe it is bolts/studs in the mount plate that you sit the mount over and then thread tube nuts on by hand before tightening with the metal bar that is supplied with those mounts to lock the axis instead of the allan key that comes with the 70. That means on those mounts you have more likelihood of having fitted the counterweight bar which more or less balances the RA axis, before pulling the locking pin out. It might or might not do damage to the mount if it were allowed to flop over to the stop, but I reckon if it grabbed your finger you would never forget the right order to do it in again!

Performance wise I am mounting about 30% of it's rated payload with my SVX80T and camera, and it flings that around like it is not even there, there is no discernible difference in the start and stop of slews with it on or off. At this point I can not test any more until I get a clear sky, currently that looks like Friday, so if that comes to pass I will set it up and test the polar camera and guider, and hopefully move on to fettling the corrector to sensor spacing for my new camera.

[Startrek]

Report sounds good so far and I bet you can’t wait to get it out under the stars
As your payload is only 30% do have any future plans to put a larger scope on board or just happy your current one ?

[The_bluester]

It will probably end up with something bigger at some point, but much longer focal length will mean the inbuilt guider will not be up to it. The inbuilt guider should be good for my current scope which allowed me to spring for the USB3 connected version in place of a new OAG and camera. That is the plan anyway. And yes, full moon or no I am keen to get it out under the sky.

[The_bluester]

A quick image as it sits. The SVX80 looks a little dinky up there.

[xelasnave]

Congratulations Paul.

It certainly looks very nice.

I have not placed an order, I came very close but have backed off mainly because I realised I don't have anything to put on one really.

My grand plans have been sensibly reduced to getting another eq6 and another zwo mono and basically be happy with the scopes I have...the roll off was to house a 16 inch on an eq8 but I am now just going to set up my eight inch and 115 mm in it and the 80 mm and a wide field camera in the small observatory I build recently...

However I am waiting on every word you have on your new mount..looking at it it looks like a piece of art you could have in the lounge room.

I can't wait to hear how the built in guiding works...the only reason I backed off was I just can not imagine waiting for something like it to arrive at the post office...

I do hope you get a run on Friday night as I can't wait to hear your impressions.

I dare not ring the supplier because I think if he has a spare I could grab it...a lot depends on your next report. But it just is such a sensible design and clearly given the balancing you noticed must mean it is going to be something else when tracking.
Again congratulations.
Alex

[The_bluester]

As a mate has pointed out, the Celestron tripod under it is no oil painting by comparison, but it will be OK until I can gather up some cash for a Tripier for star parties, I have a nice pier plate that I bought with it for when I get a second pier in here at home. I was saved from spending that extra right now by the tripier being backordered like just about every other bit of astro gear you can think of. I suspect when the COVID crisis is over there is going to be an absolute bonanza of near unused or totally unused astro gear on the market! You have to assume the percentage of people who buy and then never use will be similar to before, just so many people are buying stuff!

Really hoping that tomorrow night gives me an opportunity to get it out and start testing it. The cloud forecast is still looking promising and with only about 5KMH winds, so all going well I should be able to get some idea on how well it tracks both unguided and using the built in guider. Saturday night looks promising too, so I might even be able to get my camera spacing dialled in as well to be ready for the next new moon if the weather is OK. Then I just have to work out cable routing and lengths, and make up some new power cables to go from the puck to the camera, the focus motor and the heater.

The easier balancing has me looking into T series timing pulleys and belts to move the focus motor into a better position directly over the OTA. I should measure the knurling on the original coarse focus knob to see if it would work with a belt, otherwise two pulleys and a belt will be the go.

[Fox]

Congratulations Paul, I believe that mount has the built-in iPolar scope, maybe you can give us the low down how you find it goes with a Sigma Octans polar alignment? Thx, Fox

[The_bluester]

Yep, it does include the ipolar, so I will see how that goes on Friday, first setup step really. I can probably then let it run unguided in Dec and see how close I get it by a drift check.

[The_bluester]

Well, a few more impressions as I was able to use the mount last night. My only real issue so far is that like most people, it appears I need to go on the hunt for the "Right" USB cables as USB3 can be finicky. I had a few connection issues to the camera until I changed the PC to mount cable to a USB2 one.

Ipolar is dead simple to use, though I can not say how it will behave if you can not see the pole as I have a clear view of it. It was as simple as connect, take a dark frame, uncover the camera, follow the directions to find the axis of rotation (Not needed subsequently as it stores it like the Polemaster software does) and start aligning. Aligning the mount itself was dead simple. The only finicky bit is that tightening the alt locks tends to move the alignment (In both axes) but I found that even with them tightened in a way that it is going to take a real bump to move the mount, the alt screw would still move the axis without enough effort to be worrying it would be doing damage to the jackscrew. Azimuth is a complete snap with the az adjustment screws, light years ahead of the AZEQ6 design of cranking the whole mount head around. Subjectively, the final adjustments I was making were very small, but it is hard to compare as they are much easier to make than with the Atlas, the concept of which really comes from the "EQ-X" design that you would have to regard as "Brute force"

The guider took a bit of fiddling with, I had some issues with returning blank frames, I changed to "Windows WDM style webcam" instead of "iguider" and then selected the iguider camera in that and that seemed to be dead stable. Maybe early version firmware needing some work, maybe finger trouble on my part. After that it calibrated just fine (Which took a while due to my previous settings on calibration distance, cal data image included here) and just worked for the rest of the night. Guiding was a bit all over the place at about 1" RMS but the sky was pretty mobile looking last night so I am not thinking that is indicative of what I might be able to get. Even if it is, at a pixel scale of 1.6" per pixel on the main camera that is still well under one pixel RMS error. Subjectively, the test images from last night at 1.6" per pixel and 300 second subs all have round stars. I was concerned that the guidescope lens might dew up but no sign of that, and last night was pretty cold and damp. If it gives me any trouble I would be able to adhere a small heater to the puck, next to the guider. It is possible that the heat from the guide camera inside the puck is enough to keep it dew free, the lens is set well inside the puck so that acts as a fair dew shield.

I had one issue where the mount simply stopped responding to the driver, but I had been fiddling around for hours, disconnecting and reconnecting stuff, I restarted the ASCOM driver and reconnected and it then just kept on working from about 11PM when I went to bed to 6AM when I woke up, including an unattended meridian flip at about 2:30, Voyager just flipped it, recentered and kept on trucking. I did set up a dummy flip before I left it going alone, just to make sure it was going to behave.

Pointing wise, the first thing that I did in Voyager was a plate solve and sync on a star in the Southwest, I then sent it on a blind slew (Rather than precise pointing) to a star in the east which landed within half a degree of the target, which was probably 120 degrees away, that is without any pointing model running on the mount, just what amounts to a one star alignment. I never saw more than two iterations on a plate solved point to get within 40" which is my carry over accuracy setting from the Atlas mount.

So, initial use impressions are positive. I am sure there will be some firmware updates to come given this would be very much release 1.0, but the mount is usable and useful straight out of the box.

[Startrek]

Paul
Positive report on the new rig
In regard to USB3 cables , I’ve tried a handful of different brands from $60 down to $15 and the only one that has “bullet proof” performance is the Startech active USB3 cable ( see attached )
They are ridiculously expensive but they WORK !!

Cheers
Martin

[The_bluester]

Thanks, I will look in to that.

On the previous mount I had all sorts of weird issues at one point with a dud cable, like being able to see my focus motor and guide camera through the USB hub incorporated in the main imaging camera, but not being able to see the main camera itself! That was without a mount hub to complicate things. I may sidestep the issue (If it works) and just go to USB2 everywhere for now, if that keeps it all stable. I have a lot of new gear here at once so the niggles could be coming from any part of it!

[The_bluester]

First light image, 300 seconds X 51 subs, nice round stars. Background is horrible as it may as well have been a full moon.


https://www.astrobin.com/full/m3c0wt/0/

[Fox]

What a great 1st report, and image! Thanks Paul

[Startrek]

Paul

That’s a great image with your new camera
You must be pleased
Well done !
I couldn’t even guide last night , so much smoke haze around and the moon overhead , guide star fading in and out plus HDF jumping around like a yo yo
Going to wait a week until the moon is gone
Martin

[The_bluester]

Pretty happy with that, it was bodgy flats (I have not got them nailed yet for the new camera and actually gave dawn flats a try in Voyager for the fist time) and an 80% moon. I will have a proper go at the same target next time opportunity knocks without moonlight.

I was hoping to have another go last night and see if I could get round stars at 20 minutes but it was so windy all night that I just let it run and guide for a couple of hours to ensure there were no unexpected disconnects or other untoward happenings, it just tracked and guided away on Antares until it got down a bit then on 47 Tuc for another couple of hours after that, meantime I was re setting up the SCT for my son to use. PHD log viewer says even in the wind I averaged 0.96" guiding. Same as the night before when it was still! I have yet to spend any significant time fiddling with PHD2 settings to try to nail the guiding down better, but sub arcsecond out of the box is not bad.

[chromus]

"Active" USB cables are smoke and mirrors, they more often than not lead to issues. The USB 3.x standards don't specify a maximum length, instead relying on the fact that the controller will fall back to USB 2.0 specs when the USB 3 specs can't be met.

What this means is you end up expecting 1 thing and achieving another. USB2 is limited to 400ish Mbit/sec which is a long way short of 3.x which should be around 5 Gbit/sec. When you start trying to cram guiding pulses, guiding images and astro imaging data down that limited bandwidth it will inevitably cause issues.

[The_bluester]

Well, in my experience so far, having dropped to a USB2 cable at the mount end, there have not been any issues apparent so far with the USB2 speed with around 50Mb image frames every couple of minutes, guider frames every few seconds, guide pulses whenever they happen, mount control and position reporting to the driver etc.

That said, I will be working on cables as I would prefer to maintain the USB3 bandwidth if I can.

[The_bluester]

So far I have only one thing I could call a gripe. The guide camera requires you to drill into it's driver to change the gain and the exposure time needs to be set in the camera driver as well (In addition to doing exposure time in PHD2, the iguider manual says to ensure they match, though I spent quite a bit of time on Saturday night with PHD set at 3 seconds and the driver set at a shorter time)

The gripe is that the camera driver settings do not persist through power off, so you need to set them each night. I checked the manual and it is expected behavior, hopefully something that a future firmware update changes. In the meantime or if it turns out to be a characteristic of the camera in use, I can live with it.

Obviously if I were to whack on a long focal length scope it would not apply anyway as I would need to use an OAG and the iguider would sit there capped.

[The_bluester]

I finally got another chance to use the mount last night and it is turning out to be one of those "Transparent" bits of gear that you just set up and leave to go. The only gripe I have remains that you need to set exposure time in the guide camera control panel as well as in PHD and the settings don't stick on reboots. Relatively minor and I suppose if it really offended me I could always get creative and do a homebrew between the ioptron optics and a de housed ZWO or QHY guide cam. I am very unlikely to do that having worked out settings that work for me, and it really only takes 30 seconds to set up at the start of the night.

Guiding last night ranged from about 1.5" to about 0.6" and I think was mainly seeing influenced and there was some wind to contend with. At worst it was still sub pixel RMS total error for the imaging camera.

Aside from that, I just set up, balanced, powered on, polar aligned and go. The built in homing sensors meant that a "Find home" command was all that was required before jumping straight into precise pointing via plate solving for the first target without having to do an initial plate solve and sync to start the night.

[The_bluester]

Well, I think I will finish off for now. I have had two more nights and it has been a pain free experience. Last night was around 1" guiding, which I think is perfectly acceptable out of a 120mm focal length guider, particularly when I am imaging at about 1.6" per pixel, every sub I shot last night had round stars and after all, that is the point. I need to set up under a moonlit night soon (So as not to throw away good dark sky imaging time) and just fiddle with the guiding as I am sure I could improve it with tweaks and fettling, but even as it is, it is performaing perfectly well.

The only "Issue" I have come up with I am going to document with some logs and feed back to iOptron via my vendor (As they might get some attention) as there appears to be a minor firmware issue. There are various selectable park positions, none of which I like, but you can set a user defined park position. The issue is that if you set the "home" position (Counterweights down, pointed at the pole, my preferred park position) as the user defined park position it does not park properly, it goes to the correct position but then keeps tracking. Offset the user defined park by even a degree or so and it parks and stops properly. Small beer if that is the worst thing it ever does.

Aside from that, I spent much of last night fiddling around and sent goto after goto after goto and it just did what it was told.

[jahnpahwa]

Sounds like a good outcome :)
I'd be keen to keep reading your thoughts here if you care to keep documenting them, especially with the fettling you do and what that achieves :thumbsup:

[BinaryBill]

Hi Paul,
Any updates on the mount? I also have an AZEQ6 GT and have it tracking really well (0.4-0.7) all night but was after a little more carrying capacity, the CEM70G is top of my list.
Cheers,
Bill.

[The_bluester]

I am quite happy at this point. There were a few early software and firmware niggles, some resolved, some easy to work around. There is a new revision of the motor control boards that reduces a tendency they used to have to oscillate slightly on the RA axis (Seemed to be as the motors went over each full step they would "Snap" to the full step where the micro steps in between did not) The park position issue listed above remains, I just selected one of the preset park positions instead and it parks perfectly every time.

On a still night with a 10"F4 newt on it using an OAG I regularly see 0.5" or better, it was running last night and PHD2 was reporting 0.36" total RMS using the PHD2 PPEC algo.

Once I worked out it's minor peculiarities, it just works.

[toc]

With the Park position - Ioptron support told me that you cannot park in the Zero position - you need to be slightly off Zero before it will park. Iv'e confirmed this behavior.

[toc]

I've had two CEM70's - first was a non G, and second was a G. Both were/are very good performers from my POV.

Niggles:
- iPolar is a great system in theory, but at least on my copies of the mount not accurate enough to use by itself.
- method to attach the mount to tripod/pier is annoying
- I wish the knobs to tighten the OTA were on the opposite side

[The_bluester]

I never got a response from iOptron but I did work that one out for myself. At the time the commander software tended to "loose" park positions including custom ones and default to what is a very strange (But safe) park position, so in Voyager I was sending it home instead of parking it. It seems to retain your selected park position properly now so I park it in one of the pre defined ones as I got used to it parking there. The trap to sending it to the home position instead of parking it is if the guider is not shut down and sends a guide pulse it restarts tracking! I came up with a work around in a Voyager script to ensure that the guider was stopped any time it was sent home, but when parked it does not respond to guide commands or restart tracking.

The default park position if it lost it's brains is 0-0 alt-az which would make sense in the northern hemisphere, but here it results in the scope being parked with the counterweight bar horizontal, scope on the east side of the pier and pointed backwards!

I have found the ipolar to be accurate enough to avoid field rotation with 20 minute subs at 1100mm focal length. The fiddly attachment method to the pier does not honestly bug me though moving the altitude locks 10mm would be better. I cut the handle off a long, ball headed allan key and that makes it easy to start the bolts, only needing the original to finally tighten them. Funny enough I never noticed the saddle bolts being a pain on the side they are, but now I think on it it would be easier of they were on the other side. I tend to stand on the east side of the mount and hold the scope with my left hand, reaching around to the far side with my right to do them up.

[metalage]

This is a very interesting thread! I have recently done some extensive research on these CEM70 mounts and intend to purchase one with the NUC option in a few weeks time. Mainly as I can swap this out at any time should connection standards change and all NUCs should have stable USB 3 Ports.

Glad to hear the iPolar works allowing to easy and fast setup. This was another bonus which led me to the mount and will be much faster than drift aligning my current HEQ5 Pro.

Do people here have advice on the base they use? I’m tossing up between the iOptron tri pier or the heavier 360 version that has an anodised paint finish?

[Sitt]

I use the Tri-Pier 360 which is very stable plus should I upgrade mounts down the track I'm future proofing myself. One mod that I recommend is getting a pier plate adapter as the standard mount to pier fitting is very fidly. I have the CEM70EC btw with guiding at around 0.23-0.30 RMS Error on average
https://www.siderealtrading.com.au/product/astroworx-ioptron-pier-adapter-plate/

[The_bluester]

How does the mounting method change with the plate (I have one of those too on my pier but it uses the original attachment method on the mount itself) I honestly don't find the mounting method overly fiddly, and I set mine up night by night. I cut the L end off a long ball headed allan key to suit the mounting bolts and it allows me to start ans spin down the mount bolts easily, then I just nip them up using the original allan key that comes with the mount.

Regards the tripier versus tripier 360, if the 360 is all anodised finish then it will probably stay looking nicer for a lot longer than the painted finish parts on the standard one. Do the legs fold up in a way as compact as the standard one? On the standard one you remove the bottom portion of the legs and stow them inside the pier which makes it smaller to store.

[Sitt]

So, if you adapted your Allan Key to suit then you must have found iOptron's method of securing the mount to the Pier fiddly?
When using the Adapter Plate, it’s a simple case of 4x bolts with easier access than iOptron mounting method. The mount is permanently fastened to the Adapter Plate via the two screws in the base of the mount. Its then a simple case of removing the 4x bolts and lifting the mount and adapter plate as one. A lot faster and nowhere near as fiddly.

The legs of the 360 don't detach like the smaller version, they fold along the Pier's length for storage. I've never used the smaller Pier but by all accounts the Tri-Pier 360 is a lot more robost as its max payload is 165kg whereas the Tri-Pier has 100kg payload

[metalage]

Interesting about the adapter plate. Thanks for the link, I’ll look into that tonight. So you are finding the EC version’s performance really good then. From what I read there was early problems with EC versions and PHD when guiding. You didn’t experience any problems with this? On the Face of it you would think that an encoder to minimise PE on the RA axis would be a really good thing but from some of the online stories (mostly with the CEM60 mid you) it has made me nervous about purchasing one.

Looks like the 360 version will be the way to go :). Thanks.

[The_bluester]

I would call it somewhat fiddly, but not enough to rearrange my pier to be taking the adapter plate off the pier instead of the mount off the adapter. Even with a normal allan key I only find it about a minute or so of work to put the mount on the pier, just it is quicker and easier to start the bolts and run them down to finger tight with a straight ball head key.

I am thinking of buying a tripier for when we can get back out to star parties, I did have it set up to mount on the tripod from my old CPC925, but I remounted and sold that scope. I doubt I will ever top 100KG of load so I will probably buy the regular version not the 360, it is a fair chunk of money for what for me would be functionally identical, just prettier.

[Sitt]

No problems with PHD2, everything works as it should. Attached screen shot of PHD2 taken from my last session.

[AdamJL]

good grief, that is impressive guiding!!

[The_bluester]

Wow, that is pretty flash looking guiding. I had heard the issue was with the encoders output more or less over riding the guiding. People were reporting behaviour like PHD would make a correction, then the mount would come back again. With guiding like that you would have to say it looks like they have the encoders playing nicely with external guide inputs now. I could never see why they shouldn't work right, unless they implemented them really strangely, guide inputs are really no different to pressing a key on the hand controller.

[Sitt]

I found the key was long exposures in PHD2, I typically expose for 6-7 seconds. Don't get me wrong, the mount isn't without its flaws as I'm sure you found but overall I'm pretty happy.

[metalage]

That is amazing guiding! Thank you for sharing the graph. What do you experience with guide camera exposures sub 6 seconds? Do you see oscillations in the guiding graph etc.?

[Sitt]

Shorter exoposures increases Total RMS Error

[The_bluester]

I was actually wondering which would give better real world results. I was just digging in to if I can run two instances of PHD2, one connected to my OAG camera and one to the inbuilt iGuider cam and guide it via various settings on the OAG and monitor the real world behaviour via the other.