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iOptron CEM60-EC review blog

Please note that I’ve published a review of my iOptron CEM60-EC.

Latest news:

Updated firmware released 30 August 2014, which has resulted in further improvements in tracking, among other things, along with new ASCOM driver and PC control software.

24 April 2014

My new iOptron CEM60-EC arrived today and I believe I am one of the first consumers in the UK to receive the mount.

The CEM60 ships with a printout of the mount’s RA periodic error as measured at the encoder.  The specification for the high resolution encoder version that I have is 0.5 arcsecs RMS and the graph supplied with my mount suggests it is comfortably inside that at 0.338 arsecs RMS and +/- 1 arcsec peak-to-peak.

My initial impressions of the look and build quality of the mount were positive.  It is certainly not as aesthetically pleasing as the Avalon mounts and there are some casting marks in the casing that were remarked upon by the beta testers but the mount will live or die on how it performs and not what it looks like.

Before removing the mount from its case you are warned that you must engage the RA worm by rotating the gear switch knob fully counterclockwise.  Beware though: the manual has a photograph with an arrow incorrectly pointing at the counterweight bar locking screw.  The RA gear switch knob is the black anodised knob shown below circled in yellow:

The mount is a little difficult to get out of the case the first time but you can lift it by the underside of the base plate and top of the saddle.  It’s pretty beefy but is more compact and much lighter than the CGEM.

The power connector on the mount is threaded but neither the 12v cable supplied with the mount nor the mains power cable (which I understand won’t normally ship with UK mounts - the US version needs a standard figure 8 receptacle and is good for 240v) have a threaded collar and the collar on the CGEM power cable doesn’t get close enough to locate the thread - drat!  First suggestion to iOptron though this mount has encoders so maybe accidentally pulling out the power cord half way through a session won’t be quite as disastrous…

There are three immediate things I need to sort out:

Firstly, like most higher-end mounts the CEM60 doesn’t ship with a tripod as standard.  The specifications for mounting the head are given in the user manual.  I decided to have an adapter made from aluminium plate so that I can use the CEM60 on the tripod that came with my Celestron CGEM DX.  The DX tripod, shared with the CGE Pro, is pretty substantial with 2.75” stainless steel legs and a sturdy leg spreader and looks to provide a more solid platform than iOptron’s field tripod.  Having the adapter custom made to order is also less expensive than a new tripod… but I only ordered it yesterday so I can’t set the mount up just now.

Secondly, I’m unsure whether the 9.5 kg counterweight supplied with the mount will be sufficient to balance my heaviest imaging rig which would just about balance with the 10 kg weight supplied with the CGEM DX… The counterweight bars for the CGEM DX and CEM60 are similar in length but of course the CEM design is completely different to a GEM so I have no idea what the impact will be and some of the pictures appearing on the internet lead me to believe that I may need extra weights.  I do have the original CGEM DX weight and a Geoptik counterweight which are both a bit oversized for the 28mm diameter counterweight shaft of the CEM60 but can be pressed into service if necessary.

Finally, the mount is still very new and the firmware is being worked on in response to feedback from beta testers so I needed to check the hand controller to see what version of the firmware is installed and update it if required.

The hand controller connects to a PC running Windows using a 4p4c RJ9 serial port to RS232 cable.  The supplied cable is about 1.4m long and is very good quality (much better than the Celestron version).  My handset had version 140411 of the firmware installed and the latest version is 140423 but this hasn’t been released to the public yet so I am going to contact iOptron support to see if I can get hold of it.

I like the fact that the cable for the Go2Nova® 8407 hand controller has standard 6p6c connectors, straight wired, on each end so it will be easy to get a longer cable if required; the Celestron NexStar controllers have a shortish curly cable hard wired in to the handset which drives me nuts and while the cable supplied with the Go2Nova® is similar at least it will be easy to swap it out.

25 April 2014

I’ve just had my first proper play with the Go2Nova® 8407 hand controller and I really like what I am seeing:

On the downside, there doesn’t appear to be a menu option to select the orientation of the OTA and I’ll need this to use a side-by-side set up.  I think it can probably be done by rotating the saddle, but that would be a bit of a pain, I think…  Phillip Easton on Cloudy Nights suggested that I “release the clutch and rotate that DEC axis 90 deg, lock the clutch, then turn off and on the mount to reset zero” which - if it works will be absolutely fine (though I think an option in firmware would be good and presumably a relatively easy fix - though software tweaks are never as easy as you think they’d be…)

I am also used to connecting my Celestron mounts directly to Stellarium to control them from the planetarium software and I was keen to set up Stellarium control using ASCOM…

I couldn’t connect to the mount using my Windows 8 machine, but the COM port was recognized using a laptop running Windows 7 (my RS232 to USB converter has a Prolific chip set).  However, I couldn’t get ASCOM to identify the mount and instead was getting an error stating that ASCOM couldn’t find an iOptron mount…

That’s it for tonight.  Not much progress but I am expecting that with a mount that’s new to market.

30 April 2014

Another chance to play around with the new mount.  iOptron have updated the firmware again, now to 140429/30 so I updated the hand controller, and the main, RA and DEC boards.  All looking good and it was a straightforward process.

It had been suggested that the problem I was having setting up computer control of the mount may have been due to using an older version of the ASCOM platform (I had 6.0 installed and the latest is 6.1).  So I updated ASCOM, but it turns out my problem was that I was connecting via the hand controller - which is how it works on the Celestron mounts.  The iOptron has a direct serial port on the mount and when I connected to that everything works with no problem.

I did notice that when the mount is tracking it plays some random music that sounds like an very poor 80’s computer game.  It’s very quiet but I suspect it could get quite annoying.  At least one other CEM60-EC owner has reported the same ‘feature’ but at this point it’s not clear whether they are all like this.

I ordered a couple of extra iOptron counterweights that have arrived too so I at least know I’ll be able to balance the mount.

1 May 2014

Received an unexpected package from iOptron today containing new main, RA, and DEC control boards and a collar for the polar scope with a bubble level attached.  My mount already has the polar scope collar attached and circuit boards that were the latest ones supplied to beta testers but it turns out that the boards sent to me are all updates (marked V1414); it turns out that the boards were sent to me by mistake and are just another production run of the same boards supplied with my mount.  But I didn’t realise that until after I’d already swapped the boards out.  It’s not a difficult job but I was being very careful so it took me about 90 minutes.  Turns out you can only swap the RA board with the main board removed so I did waste some time there having replaced the main board before attempting the RA…

The adapter to allow me to put the mount head on my CGEM DX tripod is still a week or so away. Fortunately the weather sucks so I’m not missing any imaging opportunities but it would be good to get a telescope mounted up and give things a go…

24 May 2014

So my tripod adapter arrived and - amazingly - that coincided with a few hours of clear sky.  Knowing that I only had a few hours and the forecast for the next few weeks is poor, I decided to crash right in and try the mount with my EdgeHD at its native 2.8m focal length.

The mount is very easy to balance as there is almost no friction in either axis with the worm gears disengaged.  The bright star polar align also worked very well and the Alt and Az adjustment bolts are very precise - certainly a huge step up from my CGEM DX.  Also - and very impressively - there is almost no detectable backlash even at this focal length.

Even with a one star alignment, GoTo’s placed the target comfortably in the field of view of my Atik 460ex using the 11” EdgeHD (field of view 15.33 arcmins x 12.26 arcmins) which is encouraging…

The first set back was that I couldn’t get the built in cable management panel to work.  I’m not sure why as I’ve tested it indoors since and it’s fine; the 12v input doesn’t seem to be the 2.1mm or 2.5mm jack I was expecting (EDIT: turns out it is actually a standard 2.5 x 5.5mm DC socket) so that needs investigating (stupidly I hadn’t tested this).  It also seems a shame that to use the cable management panel you need to have the polar scope cover removed - surely there was a way around this in design?

Anyway, I had to run USB and power cables to the imaging gear separately and that would have meant that the mount wasn’t perfectly balanced, but I was worried that re-balancing would mean I’d have to realign and I wanted to get at least a few sub-exposures under my belt before the clouds rolled in.  So I ploughed on and decided to do a run at M63 - The Sunflower Galaxy in Canes Venatici.

I was guiding using PHD2 and didn’t spend too much time tweaking settings.  Here’s the result (16 x 500s luminance and 8 x 180s each of RGB).

Now actually the stars are not completely perfect, but they are much better than I ever managed to achieve at this focal length with my CGEM and the best results with the Celestron mount required me to unbalance the mount and only guide in one direction in DEC and to guide on a bright star with short (1 second or so) guide camera exposures - this was captured with a faint guide star with 5 second guide exposures.

I was obviously hoping that a step up in price would result in a step up in performance and that seems to be the case…

I did try unguided exposures and the mount started wandering off in RA so I think my polar alignment was probably off, but in any event iOptron are still working out some problems with the encoders on the EC mount so maybe that will get better anyway.

30 May 2014

Nothing but cloud so no more testing under the stars...  Not sure what the problem was with the cable management panel - for some reason the USB hub on the DEC axis wasn’t being recognized.  It may just have been a faulty USB cable or a problem with the laptop as I’ve tested it inside and everything works perfectly.

The 12v input for the panel is definitely a 2.5mm x 5.5mm jack, so I’ll be making up a cable with a 2.5mm plug at one end and an 2.1mm on the other to connect the CEM60 to my Mount Hub Pro.

I’ve made up a short ST-4 cable to bridge the guide port and the RJ12 input socket having sourced some flat grey 6 core cable that’s very similar to that used by iOptron to connect the DEC axis.  Plenty of cable left if anyone wants me to make one up for them!

8 June 2014

A bit more practice with the mount - this time an imaging run on M101:

7 x 600s subs with my EdgeHD 11 (with 0.7 reducer) and Atik 460ex.  Not bad!

10 June 2014

A clear night under a near full moon so a good opportunity to put the mount through its paces.  DEC guiding is excellent, but the RA - while acceptable - still isn’t quite as good.  I was getting an RMS of 0.4 guiding at a focal length of 1960mm and 0.55 on the RA axis - still appreciably worse.  Rumours are that the option to enable RA guiding only disables the encoder while guide commands are being sent and that problems with the encoder are causing trouble.  iOptron are supposed to be working on this.  I obviously hope that’s the case rather than a mechanical issue with the RA worm / ring gear.

I also have a major gripe: as noted above the power supply for the cable management panel is a standard 2.5mm x 5.5mm jack.  Again the thread on the panel connector is not long enough to use a lock ring connector.  The fitting isn’t particularly tight and the cable hangs near vertically.  Add to that the fact that the jack rotates with the RA axis and it is a recipe for disaster, or at least severe annoyance.  I had the plug fall out on me a couple of times while setting up and it also fell out 3 subs into my imaging run, so a clear night mostly wasted.  It would be so simple to fix this by using a jack with a longer thread…

On the plus side, I’ve been keeping an eye on how long it takes for the GPS system to lock on to the satellites; reports on other iOptron mounts have indicated that it can take quite a while but my CEM60 tends to hook up in less than a minute (there was one night so far where it did appear to take 3 or 4, but I actually wasn’t timing that night).

14 June 2014

iOptron have sent me the latest version of firmware (hand controller is 20140527, the main, RA, and DEC boards are 526).  I had a bit of a frustrating night as I had a problem with guide commands - I was using the mount cable management panel and somehow south guide commands were being interpreted as movement north.  I checked the ST-4 cables I was using and they seem fine, but by-passing the cable management panel solved the problem.  Too soon to say if the new firmware was responsible or if there was something else awry…

The great news is that it appears that RA guiding has improved and now matches DEC.  I say ‘appears’ because the clouds rolled in after a single 600s sub but during that exposure guiding on both axes was excellent.  I am really excited to properly test if this firmware update has solved my RA guiding issue but as usual the weather isn’t playing ball…

Word from iOptron is that the setting to allow RA guiding disables the encoder for around 3 seconds after a guide pulse has been received.

29 June 2014

A promised clear night was cut short by cloud after an hour.  It did give me enough time to thoroughly run through the polar alignment and GoTo calibration routines.  My polar scope was slightly out of alignment with the RA axis, but the polar scope is impressive and it’s very nice that the handset shows you where Polaris should be (previously I’d used Jason Dale’s Polar Finder program, but don’t need to now!)

The problem with guiding when connecting together through the accessory panel persists.  Having checked the cables again it appears that there is a hitch with the mount wiring - it can’t be the firmware as iOptron have confirmed there is no firmware interaction with the accessory panel wiring.

1 July 2014

Problem with guiding when using the accessory panel solved!  I’m not sure what the issue was but I disassembled the output and input panels and couldn’t see anything obviously wrong.  When I connected the 6p6c ports up again the problem was resolved so I am guessing it was just a dirty contact.

While I had the wiring apart I took the opportunity of performing my first mod to the mount:  I swapped out the stock 2.5 x 5.5mm 12v DC socket for a 2.1 x 5.5mm socket with a longer thread so that I can use a lock ring connector.  Easy to do (in fact the easiest bit of soldering I’ve even done) and I am so happy that the 12v can’t drop out any more…

Got a good run of Ha subs on the Cat’s Eye nebula too so a good night.

21 August 2014

I haven’t adding anything on the CEM60 for quite a while - mostly because of the poor weather and work commitments but I did have a lovely clear night last night that allowed me to do some imaging with the mount.

It was also first light for some other new kit: a set of Astrodon filters and a new 130mm triplet apo refractor.  Very impressed with these additions to my kit list.  The new scope seems very well colour corrected and is a joy to use.  There have been some comments about the CEM60’s ability to handle larger refractors because of the increased moment of inertia resulting from the longer telescope tube.  I had absolutely no problems and the mount handled this scope like a dream.

I’m not sure if I’ve said it before but the CEM60 is so quite in operation - even slewing at full speed.

I had been having some trouble autoguiding the mount.  Another user has been reporting excellent results with low aggression settings on his guiding software, the mount set to maximum autoguide rate (0.8 x sidereal), and guide exposures of ~5 seconds.  I haven’t been able to replicate the results getting reasonable guiding but with the occasional spike.  However, last night I think I happened on a good combination.  I had guide exposures of a second and RA aggressiveness of ~60% but with a fairly large minimum movement of 0.4.  At my focal length this seemed to do the trick with an occasional guide command but a very nice guide graph.  Stupidly I didn’t capture a screen shot of the graph.

26 August 2014

A surprise clear night enabled me to capture some more RGB data for the image of the Cocoon Nebula that I’d been working on.  It also enabled me to test the guide settings I was using last time out.  The results were good.  Again I was guiding with 1 second exposures but with a high minimum motion value.  This stopped the guider chasing the seeing too much, but gave the odd correcting nudge when needed.

I remembered to capture a couple of guide graphs (click on the images to enlarge which should allow you to read the guide settings).


The first of these shows the guide graph at a pixel scale of +/- 4 pixels; on the second the y-axis is set to + / - 16 pixels so of course the graph looks much flatter.  These are at a focal length of 860 mm (as I use an OAG) using a QHY5L II guidecam.

What this is telling me is that the high precision encoder is doing a good job of managing the RA error.  These graphs don’t show it, but guide corrections were being issued infrequently - several seconds or tens of seconds apart in some cases.

I’ve been very pleased with the guiding the last couple of times out and indeed last night the mount was guiding like a dream and I didn’t lose a sub.  I have had a couple of issues that might cause trouble at longer focal lengths, though:

  1. The DEC axis was jumping by a pixel or more every now and then.  This was not in response to a guide command so can’t be anything to do with the mechanics of the mount (the axis wasn’t being driven at the time) so could have been a gust of wind (though it was pretty still) or, more likely in my opinion, that the mount was ‘teetering’ on the DEC axis.  I didn’t unbalance the mount and it’s so easy to get perfect balance on the CEM60 that this might have been the problem.
  2. When the DEC did jump off it took a while for the guider (which was set to very low  aggressiveness at first) to recover the guide star position indicating that there is backlash in the DEC axis - not a lot, but it is there and will cause problems at longer focal lengths.  Now I’m pretty sure that even this lowish level of backlash was not present when I first got the mount so either something has become poorly adjusted or I didn’t have the magnetic engagement system correctly tightened… This will need more investigation.

Here’s the final image (click to enlarge) of the Cocoon Nebula (just over 6 hours worth of data, RGB with my new TS 130 super apo refractor):

19 September 2014

Again it’s a while since I’ve posted an update - mostly due bad weather.  A fair amount has happened, though.

The latest version of the mount firmware has been released (825) and has improved tracking performance still further.  In addition iOptron has released a new version of their ASCOM driver that allows multiple connections to the mount and a utility that allows control of the mount via software which I’ve found hugely useful.  Not only does it allow you to slew the mount, but you can also alter a number of the mount settings including guide rate, zero position, etc.

Worth saying that with these recent additions I’ve gone from being pleased with the mount to absolutely delighted!  It really does seem to be living up to expectations…

Galaxies Nebulae Planetary Nebulae Solar Planetary Lunar