iOptron CEM70EC2 - guiding performance at long FL

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.

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.

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 encoded mounts who achieve extremely sharp images (all other factors being equal) with these mounts.

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

Lorenzo - Very good to know - 0.4" rms is much better than what I would expect at 2210mm with the CEM70

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

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

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?