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Hello, Looking for any users with first hand experience with the iOptron CEM70EC2 and it's guiding performance at long focal lengths - i.e. Edge HD 11 @ 2800mm or reduced to 1960mm. I'm in the market for a mobile setup mount that will guide very good with a payload up to 50lbs to capture small targets like M51. The CEM 120EC2 is also an option but would prefer to go with the smaller CEM70EC2 if it will do the job. It would be extremely helpful if anyone could provide what their typical RMS guiding errors are with this mount and similar payload & image scale under good seeing conditions. Thank you TT |
6.08
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Did you see the thread on the CEM70 from yesterday, and read what George Yendrey had to say. I realise it's not the CEM70EC2, but still a good read. |
1.81
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I am regularly guiding CEM70 @2m (C8 ) with RMS below 0.5" and the mount is out all the time for two years (just covered either snow or hot summers) . Now, if you plan to guide you do not need EC version . (in fact iOptron encoders and classical guiding do not "like" each other very much ) . Or in other words, the idea of EC2 is that you do not need to guide. I have GEM28EC (encoder is only on RA) and with good polar alignment I get up to 90 seconds perfectly round stars @2m FL. That makes me thinking that you should be OK with CEM70EC2 as it is much sturdier than "toy" GEM28EC. Can't confirm that ,as I never tried though. I am also not sure how "mobile" would 120 be if you decide to go that rute. |
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4.21
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Thank you for the reply Stjephan. Could you expand a bit on what you mean by "iOptron encoders and classical guiding do not "like" each other very much" It is my understanding that a mount with hi-res encoders should have better and more consistent guiding performance as it reduces the mechanical mount error from the equation. By better & more consistent I mean guiding performance compared to a mount without hi-res encoders. |
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1.81
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As I said, if you have encoders on both axis, you should not have any need for additional guiding. You should polar align as good as possible and that's it. It should give you reasonable exposure times with perfectly round stars. No guider, no guiding camera, just the mount. Emphasis here goes on "should". High (price) class mounts (like AP i.e.) would have absolute encoders and will make it almost perfect, but with dramatically higher price tag for the same. payload. I can speak only from the perspective of GEM28EC, where there is only RA encoder . It is light mount and I am running small refractors on it (400 -500mm FL) . With that, I do not have problems with 4 minutes frames (I am usually in Bortle 4-5 so longer exposures do not make much sense anyway). In the mount setting , you can let the mount be guided in addition to encoders (filtering guiding pulses) . That filtering should resolve possible clashes between instructions coming from guiding and encoders. I never managed to make it right. Did not put much of an effort though, as it does what is made for without guiding). So if yo want to guide and use encoders, it will take the effort to make it right, probably as much as if you do not have encoders. At the end, you can perhaps get better guiding than without encoders . But the question is why to do that as encoders will do their job without guiding for reasonably long exposures. I assume you have CMOS camera which does not require extremely long exposures like CCD. |
5.73
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| The CEM70 (and any other quality mount) that is properly conditioned - springs, belts and gears; level, solid on the ground, not overloaded and properly balanced is going to perform very well (and at the FL you mention, with an OAG). I use a standard CEM70. The CEM120 is a BEAST. Mounts in this class (and above) with high resolution encoders (as has been mentioned) simply do not need to be guided. They guide themselves, respond to fluctuation immediately and allow for equal - if not far greater - integration. Search for such mounts in the 'Explore Equipment' feature herein, and you will find members using encodedmounts who achieve extremely sharp images (all other factors being equal) with these mounts. |
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Agree with the comments that folk have made above. I also just use a standard CEM70 mount which, even somewhat overloaded with about 20 kg plus of 1200 mm F4 300 mm reflector plus kit, works well. Properly balanced and polar aligned I get guiding (multistar PHD2) to less than 0.5 arcsec RMS using a f = 400 mm guide scope -- the EC version is a different proposition of course. Tim |
5.26
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For what is worth, I'm just now imaging with my standard CEM70, a C11 @ 2210 mm, guided by an Asi120 and a 60/228 guide scope, using an Asi294mm and I'm currently at 0.4" rms for maybe one hour long. So, I think you can save your money and land on a standard Cem70 trustly. Different case if you want to go unguided or if you plan to use a very heavy rig. Ciao. Lorenzo |
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4.21
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Thanks all for the reply's - Just to clarify I would still plan to guide with the CEM70EC2 and I'm shooting with a 6200mm or 294mm and generally I stick with 300sec exposures for narrowband but would like the option try longer exposures on faint targets. I'm trying to get the best resolution possible out of my Edge HD 11 @ 2800mm & 1960mm when I travel to a dark sky site (i.e. under ideal conditions) and I am at the stage where the weakest link in my setup is currently my mount. I'm not ready to get a 10 Micron yet but I'm looking at a mount with dual encoders and the CEM70EC2 seems to fit the bill on paper but as they say the proof is in the pudding so any first hand guiding data for this mount would be good to see before spending the money. |
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4.21
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| Lorenzo - Very good to know - 0.4" rms is much better than what I would expect at 2210mm with the CEM70 |
1.81
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I have the CEM70-G and I am experiencing outstanding tracking/guiding under good seeing conditions, often at 0.20 rms or even lower. I run the mount as it was out of the box, no tweaks. I discovered that a longer FL guide scope (400 mm) made a big difference compared to a 200 mm. Clear skies, Steen  |
3.81
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I actually have both the CEM70EC2 (bought in Sept 2022) and a new CEM70 as well. I'm using it with the Askar 130PHQ + guide scope setup. The payload is usually in the 32-35 lbs range. My CEM70EC2 has never liked guiding with PHD2. I've been through configs and forums. When I was able to get it going, it still seemed to flip out occasionally. It was definitely a problem with Dec axis primarily. Ioptron support has been communicative, but couldn't offer me much of a solution. Now I primarily use it without guiding and stay with 180s subs. I can confirm that works very well. If i push to 300s or more, drift will start to show. It works, but it's disappointing, as my initial goal was getting some good long guided subs (5-10min) Hence the CEM70 purchase. I still think this mount is solid and has a great payload to weight ratio. I actually just got the CEM70 and will be testing out normal guiding tonight. Definitely hoping for similar results to what you all have shared |
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3.81
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Nick Grundy: @Steen Knarberg Could you share a little more detail about your setup? payload? guide camera? using tri-pier or something more substantial? |
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1.81
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Hi Nick Off course. I have the mount sitting on a wooden pier I built my self. It works wonderful. Image here: https://photos.app.goo.gl/82GN9TioD2tbyzGz5 The pier is made of epoxy laminated Douglas and measures 120x120 mm across and is 3.5 meters long, with a 2 meter deep concrete footing. Very solid. I haven't done any polar alignment for months and I see absolutely no sign of that being necessary. I use NINA three point PA. When I built the pier I ran into comments about wood not being good for a pier because it would warp. That assumption did not turn out to be a problem. At least not in my case and with the way I chose to laminate the pier. On top of that it's a joy to have a beautiful wooden pier in stead of one made of concrete. At present I have two scopes, the TS 130 mm F7 Apo (0.8 reducer) and a TS 203 mm RC. Currently I use the APO most of the time as it's so easy to use and is fairly fast. I use PHD2 for guiding, the cheap SW 80/400 mm achromat and also the ASI120MC as a guide cam. I have found that using a longer than recommended focal length guide scope improves guiding considerably. I once read an article saying that PHD2 has less trouble locking on to a slightly out of focus star that one being perfectly focused with sharp edges. Personally I think there is a lot of truth in that from what I have observed. PHD2 settings are very basic. On RA I currently use predictive algo, but the normal hysteresis also works very fine. On DEC I use the default. Numbers are those reached by running the guide assistant. I reduced the Min move numbers about 10%. The guide assistant reports no backlash on Dec BTW. What I think is very crucial to understand, and accept, is that there are many nights where it's seeing that limits your guiding and not your setup/equipment. I see a lot of people going to extremes doing all sorts of things to minimize cable drag, vibrations etc. but at the same time not being aware of what the atmosphere does to guiding. Also I see tripods standing directly on lawns etc. which has to go wrong. When I used I tripod I had it standing on what I regarded as a solid paved surface held down by a another added 10 kilo weight. Even then I knew that every night I had to do PA because of movements in the soil below due to changing temperatures, moisture etc. So I have to say that a pier is one of the best cheap investments I have ever done for my astrophotography. I think that's it. Feel free to ask if there's anything I forgot. Clear skies, Steen |
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| @Steen Knarberg thanks a ton for sharing. I like the pier, and as long as its stable, it looks a hell of a lot better than most that I have seen. Your setup sounds very familiar. I'm typically using my Askar 130PHQ at native 1000FL or my EdgeHD8 (also native until i decide i want to change that). Another user on AB recently gave me some great tips and helped me understand guiding principles recently. (thanks @John Dziuba) I'm now using an SV80 @ 300FL with an asi290. Still not perfect, but i'm generally guiding more accurately on all my mounts now. I'm actually now suspecting there are hw issues with my CEM70EC2. (see below as I've corresponded with iptron support) They haven't offered too much of an answer yet other than they think it could be possible declination backlash and asked me to verify that by visually tracking along a line then back again. I'm still lost by this process though.  On a positive note, I ran out my new CEM70W with the 130PHQ+ASI6200MM last night. Guiding was pretty amazing. It hovered around .5-.6 rms. Obviously I'm hoping to improve on that, but it's a relief having usable sub frames other than the satellite photobombs. |
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Hi Nick That Dec curve looks very strange. To me it looks as if PA is off somehow or as if some excessive guding takes place. How do you polar align? And what happens if you set Dec aggressiveness to 0? Could you try to change the curve units to arc secs in stead of pixels. Also we need the corrections to show, otherwise we're blind to what's going on. I notice that you use 5 sec guide intervals, which seems to be pretty long. I would suggest 1.5-2. Also check that the guide scope is bolted tightly to the scope and that the guide cam is not loose somehow. And finally, how does a EC mount work with PHD2? Are there some special settings or guide algo to consider? |
2.41
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I run both a CEM70EC and CEM70EC2 regularly with a WO FLT132 and an Edge HD 9.25 2350 focal length un-reduced. For both mounts, guiding appears to be .6 or better (.4 is not uncommon) on a consistent basis even with moderate wind (which is why I went with an EC version). I've had more time running the EC mount with an Edge and with zero dewshield on, but the results are pretty comparible with the EC2 version. I can't conclusively say the EC2 is so much better than the EC version yet. One thing is for sure.. these mounts perform much better if perfectly balanced even in the 'Z-axis' by using the tiny little iOptron add-on counterweight at times. The other thing with these mounts is that they do not like be corrected on a fast, quick basis and need time to react. PHD2 settings of 3-5 second exposures are critical. I've saved a lot of time by following this article: https://www.cloudynights.com/topic/765943-phd2-settings-for-cem120ec2/#entry11102839 and I see the same results by following the poster's advice. For planetary where I don't use PHD2 at all, I've come back hours later after aiming at a planet with Edge 9.25 and seen hardly any drift due to tracking. Polar alignment needs to be great of course. I can't say I've had the same level of results for several other mounts. I did consider a CEM120EC for a possible future observatory, but it really feels like overkill and I set up and tear down in a backyard and driveway nightly or every few days. If you need mobility, the CEM70 does the job and saves you a lot of back pain. I can one hand it to open a door in the garage to bring it in. I would never do that with a 120!  The Tri-pier 360 iOptron pier lets you mount multiple brands and size mounts and I have been very happy with it. I can't compare it to the 'default' tri-pier non-360 or the LiteRoc. The 360 pier is light enough to move around short distances and is extremely stable. I wouldn't take it for a hike though! |
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Hi all, Reading along with interest as I am on the journey to a good mount some time in the short to medium future. I can't justify a 10 micron .I have a friend with a CEM70W. He loves it and I have hooked my laptop upto it with a couple of clicks it is imaging !He regularly get 0.5 arc sec guiding . I am considering the CEM70EC ( encoder on the RA) but am concerned with reading different forums that there is little evidence of a benefit. I am currently building an observatory but visit a dark site monthly so need to be mobile as well. I reached out to Ioptron for clarification and here was their response. Hi ,I am a potential customer .I have never owned an =ilIoptron mount before . Your CEM70 range of mounts do come within the specification requirements that I am looking for.Sub arc second guiding is one of the criteria but I am now somewhat confused.I am looking seriously at the CEM70EC model as the PE reading on paper is recorded to be >10x better than the non encoder model HOWEVER I have been told by another owner of a CEM70 that he did not buy the Encoder model as it was not able to be autoguided. Is this CORRECT?? Kind regards And response from Ioptron=MsoNormalHi, Wes,=MsoNormalThank you for your interest in =iliOptron!=MsoNormal =MsoNormalCEM70EC sure can be auto guided with good results. Some customers who do tracking only (don’t do autoguiding) might be restricted to the EC model because of the naturally low PE. If auto guiding, the EC and non-EC models might do similar job/results. CEM70EC can be set at with dual axes or DEC only guiding (filter RA guiding), that might be the confusion of “was not able to be autoguided.”=MsoNormal =MsoNormalWith EC model, customers use (and we recommend) long cadency guiding, that is, guiding corrections are issued on intervals of, say, 5 to 10 seconds to guide out the low-frequency errors, such as polar alignment error, atmospheric refraction, thermal fluctuation, flexure, etc, and no need to use rapid guiding in order to allow the encoder working diligently between pulses and keeping the mount on track. Long exposure and cadency are good to average out the seeing and capable for very faint guide star, which is good for OAG since bright stars might not always be available for OAG.=MsoNormalWish you a healthy and prosperous New Year! Cheers Taking the above into account Guiding with the CEM70EC model should give better results ? |
