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Old 26-08-2020, 08:00 AM
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ioptron CEM70G initial impressions

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.

Last edited by The_bluester; 26-08-2020 at 11:25 AM.
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Old 26-08-2020, 08:59 AM
Startrek (Martin)
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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 ?
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Old 26-08-2020, 09:04 AM
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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.

Last edited by The_bluester; 26-08-2020 at 09:49 AM.
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Old 26-08-2020, 12:36 PM
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A quick image as it sits. The SVX80 looks a little dinky up there.
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Old 27-08-2020, 09:43 AM
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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
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Old 27-08-2020, 10:34 AM
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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.
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Old 27-08-2020, 11:07 AM
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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
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Old 27-08-2020, 11:40 AM
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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.
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Old 29-08-2020, 10:07 AM
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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.
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Last edited by The_bluester; 29-08-2020 at 10:45 AM.
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Old 29-08-2020, 10:28 AM
Startrek (Martin)
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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
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Old 29-08-2020, 10:32 AM
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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!
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Old 29-08-2020, 02:59 PM
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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/
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Old 30-08-2020, 05:51 AM
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What a great 1st report, and image! Thanks Paul
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Old 30-08-2020, 07:46 AM
Startrek (Martin)
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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
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Old 30-08-2020, 03:57 PM
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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.
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Old 30-08-2020, 05:52 PM
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"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.
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Old 30-08-2020, 08:01 PM
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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.
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Old 31-08-2020, 01:21 PM
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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.
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Old 11-09-2020, 11:48 AM
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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.
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Old 15-09-2020, 07:46 AM
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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.
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