No guide logs, but here's a link to a cell phone photo of the laptop screen taken late into a recent session. Most nights I see guiding clustering around 0.30" RMS (arcsecs, not pixels) total. Some nights are worse, likely when I have not done my part. Pretty sure everything is configured correctly. I have checked and rechecked as I did not expect (and at first questioned) these results from this class of mount. I would accept ~0.70" (or anything less than 1" really) so half of that is amazing to me.
I had to do a couple of things when I received my CEM70G to get good tracking. Here's the current typical setup:
- C9.25XLT or EdgeHD 9.25 at F/10 (I do not use a reducer), plate solving reports 2227mm focal length, sometimes FLT132 / Guidetstar 61 / OSC of some sort
- Celestron OAG / ZWO ASI174MM
- ZWO 2" 7 position filter wheel fully populated
- ZWO ASI 1600MM Pro
- Pegasus Astro UPB
- dew straps around the corrector plate and the filter wheel
- sometimes a dew shield
- CEM70G (latest version) on an iOptron Tri-Pier, set up on the lawn each night (less than ideal)
- PHD2 usually set for multi-star guiding, usually 1.5 sec exposure, and rarely do I set the focus of the guide camera (FWHM ranges from <3" to >7"); also, usually calibrate (every session due to temporary setup) just East of the meridian at DEC=0 but not always
- iPolar for PA
- dithering frequently depending on sub length, NINA for acquisition
- 5A PSU dedicated to the mount, everything else runs through a separate 10A supply
I think payload is over 30 lbs as configured above but haven't weighed it recently. The FLT132 which also rides on this mount loaded up with stuff is >40 lbs as I recall. I need to validate those numbers so please consider them SWAGs for now.
This may be a bit difficult to describe. The head of the mount where it connects to the base allows it to pivot in a dovetail interface. My mount had an almost imperceptible amount of play that got a little worse after a few nights, and became very obvious when the mount was loaded up with payload and counterweights. While it was small, there should be effectively zero play, of course. Guiding was widely variable, and error prone, over the course of an hour.
There are a couple of set screws that control the amount of play in the dovetail. I adjusted those until there was no detectable play by feel without totally locking down the dovetail. I verified this with the mount fully loaded then lifting on the c/w extension bar to feel for movement. Not scientific. When I get the mount on a permanent pier I will readjust perhaps with with a dial indicator. I set up and tear down every night, so it doesn't seem worth it just yet, especially given the results I am enjoying. I try to remember to check the c/w shaft and c/w knobs every night. Heat cycling (presumably, maybe vibrations too) causes them to loosen which can result in guiding issues. Finally, the to plate of the Tri-Pier was not 100% secure. This took a while to find and was remedied by tightening those fasteners. I suspect this may be a failure point in the future, but is not the mount's fault.
The RA axis on my mount seems pretty decent with PHD2 reporting near-zero backlash. PHD2 reports that DEC has more although I cannot detect it by feel. One of these days I'll fiddle with the worm gear engagement to see if I can reduce it. Even this DEC backlash is low based on what I see reported by other's mounts, but it is the source of deviations. PHD2 seems to be able to handle it.
Unguided subs of 5 mins are possible at F/10 but I rely on guiding anyway. Deformed stars appear now and then in 5 min subs depending upon how well I set up the mount. I have never seen issues in a 4 min unguided sub. Long unguided subs are super easy with the shorter FL refractors. I just typically guide because I feel I should and it (usually) covers up any lack of care I took during setup. Once in a more permanent set up, I'll take the time to get everything as close to perfect as possible.
I considered the CEM70G a gateway to something better later on from the usual suspects (AP, 10micron, Paramount). Had the premium mounts been available at the time I would not have purchased the iOptron. Now, I am not so sure I need to upgrade. I may do that if/when the CEM70 wears out, but even then, it's a question.
One irritating issue I am fighting is intermittent disconnects for devices plugged into the CEM70G USB hub. While rare, it happens enough that long imaging sessions have been ruined since it goes unreported by NINA (clearly at least) to the user. The errors are in the logs. I can address that by manually setting the abort on error for each command (tedious). There's no obvious way to my knowledge to send an alert to inform of this though. Maybe a log file watchdog. Issues are filter wheel not changing causing NINA to go into an infinite loop of error reporting, or focuser doing the same thing, or focuser not responding causing NINA to give up proceed to image with previous focuser position (and likely poor focus). Likely a h/w issue exacerbated by s/w design choices. NINA generally works great when the hardware behaves.
This is another topic and I have not sorted out the details yet so I'll stop there. Too many words up there already.
I hope something in these ramblings is helpful to someone.