• ASI Mount

  • AM5 - Guide performance underwhelming and varies

Hi all,

I just made the big step after years of using an AVX and picked up a ZWO AM5. I feel that the guiding could be way better for this mountand i'm sure its settings that i'm not doing correctly. I'm seeing numbers around 0.67 and then over the course of the night I'm seeing these numbers increase despite being under bortle 4 desert skies with crystal clear seeing. Polar alignment is spot on. I primarily use the Polemaster for polar aligning, and have also used the ASI AIR polar alignment tool. I strictly use PHD2 for the guiding software. Even when using the ASI AIr guider i'm seeing around the same numbers.

Within PHD2 I created a profile, ran a calibration to the south above the celestialequator as described in the best practices. After calibration, I also ran the guide assistant for about 5 minutes and applied the suggested numbers and then started imaging using predictive pec, and resist switch. As stated the numbers are slightly underwhelming and steadily increase over the night.

Looking for suggestions from people as I can't seem to find what this thing likes for settings.

My gear is a Stellarvue SVT70-IS, ASI174MM Mini guide cam, ASI294MC Pro, ZWO EAF.

Attached is lastnights guide log. The one that starts at 00:15 for 3hrs 1m was my main imaging run. After that run you can see where i'm playing around with settings, but the numbers keep increasing.

Link to the guide log
https://www.dropbox.com/s/cm1kv2zqawjfcqa/PHD2_GuideLog_2023-06-17_102840.txt?dl=0

  • w7ay replied to this.

    seaber I'm seeing numbers around 0.67 and then over the course of the night I'm seeing these numbers increase despite being under bortle 4 desert skies with crystal clear seeing....and steadily increase over the night [bolded emphases are mine - chen].

    If you are using an ASIAIR, I would recommend stopping and then restarting the autoguiding once every hour or so. When I use an ASIAIR, I usually do that when I refocus my OTA (which I do every 1ºC of temperature change).

    The reason is this: the adequate polar alignment numbers that you read about are associated with field rotation over a short exposure time, i.e.., field rotation over only 2 or 3 minutes. When you use multi-star guiding, you are averaging the centroid of multiple stars, and their relative position depends on field rotation over a much longer time, like over hours. (I had warned ZWO to look out for this when they were starting to implement multi-star guiding, and to use a very slow moving average to mutate the asterism; but as usual, it fell on deaf ears -- or, they simply don't even grok the problem).

    Basically, over an hour or two of autoguiding, the asterism of stars used in auto-guiding has changed due to field rotation. dx and dy for one star is now different from dx and dy of another star (rotated from one another). Resetting guiding (stop and restart) will reestablish a new asterism (relative position of the multiple stars).

    See if that makes the mount a bit more tolerable.

    By the way, this problem does not exist with single star autoguiding.

    Chen

        w7ay If you are using an ASIAIR, I would recommend stopping and then restarting the autoguiding once every hour or so

        Thanks Chen, your explanation is simple and logic as usual ..
        I want to know please.. is that problem solved in PHD2? how ? because you specified ASIAIR.
        Does PHD2 automatically compensate that?

        BR,,

        • w7ay replied to this.

            Hi Chen,

            I dont use the asi air for imaging, I use NINA for my imaging runs and a Polemaster for my PA process. Would I benefit from disabling multi star guiding in PHD2?

            On my run that im doing right now, i'm under clear bortle 4 skies with great seeing and after running the guide assistant and lowering my guide exposures to 0.5, i'm seeing even worse numbers. Its currently at 1.27 which is pretty much where I was with my AVX mount.

            I'm sure theres a setting somewhere that im missing and its a brand new mount to me with a steep learning curve. I just have no idea how to tame this thing and get the awesome numbers everyone else is seeing. I dont think its a weight issue either. We're probably looking at 15-20lbs. And in regards to balance, I dont even know how that could be achieved.

            Any suggestions here would be great.

            • w7ay replied to this.

              ASIMount@ZWO It i indeed a great review, but I personally am not seeing any setting recommendations in it as to how they achieved the consistent 0.4 listed in the closing. I see that they recommend bin 2 for the guide camera setting and shorter exposures.

              No mention as to what algorithms used etc. Which is a question id like to know as im using predictive pec and resist switch.

                w7ay WOW Brilliant Chen!!!! You may have just explained an issue that has had me baffled for a long time. I have been experiencing similar guiding issues as seaber mentions. In my case however probably even worse. BUT what I have noticed is that no matter how bad it gets whenever I do a meridan flip almost like magic my guiding is immediately greatly improved. I have been searching for a reason why for a while now.
                Because of the limitations of my field of view from my home, most nights involve a MF. Then after that, I only have at most another hour or so I can do any imaging on that target before some trees get in the way and I switch to a different target that then is coming into my FOV..........
                You may have explained to me why the best guiding adjustment I can make each night to improve my guiding is an MF :-))) Thanks Al

                • w7ay replied to this.

                    MrAstro is that problem solved in PHD2?

                    I have not looked into PHD code since Craig Stark open sourced it years ago. I know that Craig did not compensate for it, but then it was in the days of single star guiding, so it was not a problem.

                    Chen

                      seaber Would I benefit from disabling multi star guiding in PHD2?

                      I don't know. You will need to ask the N.I.N.A. developers if they are compensating for the slow field rotation when doing multi-star autoguiding.

                      If you are getting a long term deterioration, it is easy enough to stop imaging and resetting the autoguiding every hour or so to see it things improve (and not cause by flexure, clouds, city lights nearer the horizon, and other problems).

                      Chen

                        Byrdsfan1948 what I have noticed is that no matter how bad it gets whenever I do a meridan flip almost like magic my guiding is immediately greatly improved.

                        Hi Al -- since you don't use a strain wave drive, that could also be explained by third axis balance. I.e., third axis balance is potentially different between the two pier sides.

                        When you check for third axis balance, you need to do it for both pier sides.

                        But, it is easy enough to stop and restart autoguiding, to see if field rotation is your problem.

                        Chen

                          Hi all,
                          Can anyone clarify please..
                          If I need to change Max RA duration or Max Dec duration during guiding, Should I stop guiding and recalibrate ?
                          Thanks

                            MrAstro no need to recalibrate etc after changing durations, but after an hour or so just stop auto guiding and restart it to get asiair multistar more accurate.

                                MrAstro i dont believe so. But it never hurts if you see your numbers going up. I often do it just so it picks better stars if the numbers get worse.

                                  Write a Reply...