Hi, I recently purchased a CEM70EC2 and have it permanently mounted in my observatory. I have done a Polar Alignment with my ASIAIR Plus and ED72 F5.8 scope with ISO1600MM PRO with CFW and its close enough for now. being around 20 arc seconds or so out. My DEC curve stays fairly horizontal so PA must be ok.

I did a Calibration and that went fine but when it started Autoguiding and settled in, the guiding was not steady. I am not sure how to setup aggression for both Axes or how to fine tune them. My guiding varied in some trials in different areas from 0.5 to 1.1 rms. Since this is a dual encoder mount what settings should I try and can you please advise on how to set it up properly to guide with the ASIAIR plus.
thanks Nick

15 days later

Hi, is anyone available to answer please?
Here are my Logs..
thanks..

phd2-guidelog-2023-11-05-204347.txt
367kB

I am currently having tracking issues with my CEM25EC and via my supplier have had communication from iOptron relating to guiding (which I cannot get to work at all on my setup - but that is another story). This is the reply from iOptron;

In general, well-made mounts with high precision encoders don't benefit from aggressive (rapid) guiding and some may actually suffer from it. Guiding with short exposures are not a good approach, mostly because the mount was probably just chasing seeing effects. Mounts with encoder often produce the best results with long-cadence guiding, meaning that guide corrections are issued on intervals of, say, 5 to 10 seconds.

The goal is to guide out the low-frequency errors that arise from polar alignment error, atmospheric refraction, flexure, etc. There's no need to use rapid guiding because the encoders should be keeping the mount on track.

This guiding cadence is established by using two parameters: 1) the guide camera exposure time and 2) the time lapse property.

If you use longer exposure times, you will dampen the effect of seeing variations right away - a good starting point for you would be 2-3 seconds or so. Then you adjust the time lapse property to create the final delay between guide corrections: camera exposure time + time lapse value. If you find that the guide star drifts too much in declination, you can reduce the time lapse value or improve the polar alignment.

The time-lapse property is not implemented in ASIair PHD. I have raised this with ZWO Support over a month ago asking for the feature to be implemented but other than an acknowledgment I have not received any further updates.

My apologies if this is a 'red-herring' but I thought it may be of interest.

I have no idea why there are font changes above - apologies if that is a distraction in any way.

Yes it makes sense to use longer exposures when guiding encoder mounts as you want minimal corrections from the ASIAIR or other Guiding Software. It us good you contacted Ioptron about this. Its been cloudy here for a few weeks now and probably for another week or two so I have to tried this yet.

What I also want to know is information on the Calibration Step and MAX RA and DEC Duration figures on the ASIAIR's Mount setup page. The current ASIAIR defaults are 2000, 2000, 2000 and I have read that if you are using a ZWO mini Guide scope with FL=120mm these figures should be in the vicinity of 8000 to 10000? I know when you do a calibration, these higher values move the mount more than if you use the default 2000 values and requires less Steps to calibrate. However if you are using an OAG with the FL of the Guider being the same as the FL of the scope, then these figures should be in the range of 250 to 500ms. So info here would be very helpful and I am not sure what to do.

Also when guiding, what aggression values should I use? I would presume using lower figures such as 10 to 25% would keep the autoguiding bumps down to a minimum? Also with the Guiding Rate, should I try different values 0.25, 0.5, 0.75 x Siderial to see which gives better RMS values or just leave it at 50%?

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