Hello,
I know there are numerous threads on this forum including ones where several users confirmed that short guide exposures with short guide pulses and low aggression settings in ASIAir or PHD2 seem to drastically improve the guiding capabilities of the AM5. Yesterday I had the chance to take my AM5 for the second time to try some of these suggestions since my first attempt was very disappointing. Before getting into the details, please note that my main mount is an ioptron CEM70 with a Evoguide 50 guide scope and an ASI178mm camera. I consistently get sub .4 arcsec rms total error consistently under the seeing conditions in my area.

With this second attempt, I decided to eliminate as many variables as possible so I used the same guide scope on the AM5 setup which is also carrying an Askar 80PHQ with a PO Ares-c camera...total weight about 6 KG. The setup including the guide scope was bench balanced, marked, and mounted on the AM5 so that the COM is approximately aligned with the centre of the dovetail plate of the mount.
As you'll see in the attached log, I tried an imaging sessions with very fast guide exposures and lower than default guide pulse aggression settings and was getting the same results as I was on the first night, around .9 arcsec rms total error. I then decided to perform shorter guide runs starting with default settings and changing one parameter at a time to see how the mount is behaving. Each 10 minute run started in the same Alt/Az point very near the zenith to minimize atmospheric effects.
My conclusion from what I saw is while the AM5 benefits greatly from short guide exposures, lowering the aggression settings definitely lowers the mounts ability to respond to errors. Lowering the guide pulse durations doesn't seem to have as much of an impact as others reported. Also switching from hysteresis to predictive PEC seems to have the biggest positive impact on the RA RMS error. This seems to contradict the information I found on this forum around improving the AM5 guiding results (referring to this thread among others https://bbs.zwoastro.com/d/15711-very-large-backlash-in-new-am5/13).

Please note that when I did imaging runs with some of the settings(the guide runs in the log that have dithers are all also imaging runs), the results where acceptable given the image scale of the main imaging scope, but certainly no where near as sharp/consistent as my CEM70 (running the same guiding scope and a faster imaging scope but a similar image scale). I'm not obsessing about sub pixel or sub arcsec rms errors, I'm just trying to understand why my mount behaves very differently from others. Also since I just received the mount, I'm still in the 30 day return period in case the results indicate there's something actually wrong with the mount.

For your reference, I'm on the latest driver and firmware for the AM5 and using the latest ASCOM platform and PHD2 as well. Calibration was performed at the beginning of the session with good results (shown in the log) and the guide scope is very securely attached to the setup.

phd2-guidelog-2024-03-07-145428.txt
2MB

    eyecon I looked over the log and the minmo is too high. Switch both to 0.1px and that will help. With a higher number it does not react fast enough to small movements. Start off at 1s guide exposures and 50/50% on the aggressions and 500/500ms on the durations as a baseline setting. Disable the backlash compensation too of 1010ms.

        Kevin_A will definitely try that on the next clear night. Thank you very much for taking a look!

          eyecon do you have a photo of your PE curve you can share. Usually you can see if that Ra error is going to be challenging! Mine is challenging only due to my non sinusoidal shape and additional harmonic blips. But through careful analysis and tweaking I have tamed it nicely and that allows me good photos in most sessions except bad sky turbulence.


              Kevin_A

              This is my PE curve. Mine looks to have higher frequency harmonics which might explain the worse results that I’m getting. Let me know what you think!

              • w7ay replied to this.

                  eyecon This is my PE curve. Let me know what you think!

                  Lots of high harmonics. Could be problematical -- but with ZWO, it is the luck of the draw, and the next one could be just as bad.

                  Chen

                      Thanks for taking a look w7ay that’s what I figured, lots of deviations more frequently requiring faster guide adjustments…
                      Do you think it’s worth looking into a replacement?

                      • w7ay replied to this.

                          eyecon Do you think it’s worth looking into a replacement?

                          Did you read the rest of my comments? You need to switch manufacturer to people who knows how to manufacture precision parts.

                          Chen

                              w7ay sorry the rest of your comment wasn’t showing on my phone for some reason. Yeah if it’s hit or miss with ZWO then it might not make a difference.

                              • w7ay replied to this.

                                  As Chen said it has lots of high harmonics but a lot of the 288s period mounts have these rough curves and some guide well. So it seems in Asiair. You may get a worse mount the second time around if you order a replacement. Your mount has small PE but it is not smooth wheras higher end mounts have larger PE but smooth sinusoidal curves. I have found that with a rough high harmonic mount curve that these amateur mounts have, a lot of guiding advice does not work as well as with a smooth curve. In fact I can alter my durations and aggressions a lot and it changes nothing some nights. I am constantly testing and one definitive thing I have found is… asiair while convenient, is not good enough to tame a bad mount. You can give it all you have and nothing seems to control it when using asiair. Just make sure your Minmo is around no higher than 0.1px and disable backlash compensation unless it is really necessary.

                                    eyecon Yeah if it’s hit or miss with ZWO then it might not make a difference.

                                    It is a shame that ZWO is giving mounts that use strain wave gears a bad reputation.

                                    I have been using strain wave geared mounts since 2020, and have no problem with my four Harmonic Drive (TM) mounts.

                                    Chen

                                        w7ay Kevin_A thanks for your feedback and advice…as this is my portable mount I’m not obsessing too much about guide errors just trying to get the best results possible as mentioned earlier. My iOptron CEM70 performs consistently at sub .4 arcsec rms. Unfortunately it weighs a ton 😂

                                        Out of curiously, 2hat would you consider to be a higher end strain wave mount?

                                            w7ay they really are just amateur mounts as they are very coarse in function! And the asiair implimentation of phd2 does not help. I upgraded all my guide scopes and it did only a little to help. When having perfect PA helps more than sharp stars one knows it is best to change ecosystems if you want the best and excellent images. For me right now I am ok with 0.5 to 0.6rms guiding averages as my biggest scope is a 644mm and I do not need 0.3rms guiding to get good round stars. But when I get around to building a skyshed with a bigger scope it will be with a premium mount and not Asiair controlling it! I will use the asiair ecosystem then on my AM5 when I go to the lake to do 15mm milkyway shots with this forgiving guided rig.

                                                Kevin_A I don’t own an Asiair and been only using phd2 so far. I just installed Metaguide which in theory could produce better guiding results since it’s using the camera’s video feed with a clever centroid averaging algorithm to track rather than discrete exposures. I have a feeling this type of guiding might be better suited for mounts with higher rates of change in their PE curve based on everything you experienced and w7ay has mathematically demonstrated on other threads.

                                                      eyecon yes, the AM5 and asiair are not great but intended for fair guided portable use.
                                                      I find it silly when users put C11 scopes on them…. Seriously? Haha It is like taking a dump truck to the racetrack or a Corvette off-roading!

                                                      • w7ay replied to this.

                                                          Kevin_A I assume by premium mount you’d be looking at a more traditional worm
                                                          Gear mount? I haven’t done much research but at least what’s available here in Canada in terms of pure strain wave drive mounts seems to be the AM series from ZWO or the RST series from rainbow Astro. The RSTs are significantly more expensive the AM but I guess based on what w7ay explained on other posts, they seem to be better made and might have a better gearbox(?)
                                                          Again for me, the AM5 is the portable rig which I’m using with my portable refractor setup. My 10” fast newt lives on the CEM70 and I have had no issues with guiding at all with this combo.

                                                          It’s just always good to understand the equipment and try and squeeze as much performance as possible given the use case and price point.

                                                                Kevin_A Seriously? Haha It is like taking a dump truck to the racetrack or a Corvette off-roading!

                                                                So far, the largest payload I have put on the RST-135 and RST-135E is the FSQ-85 (dual saddle with side-by-side guide scope adding some 5 or 6 lbs).

                                                                I have received my Mewlon 180C (waited a year for Tak ' manufacturing run) and will try that as a payload. But that is the absolute max I will put on it when weather allows. I have in the past without trouble used a C6A on an RST-135. The strain wave gear should have no problem slewing the Mewlon (even C11), but guiding could be a problem, we'll see. That being said, I plan on using the Mewlon unguided on the RST-135E, though -- the OTA is just for planetary (the encoder will keep the planet inside a 2.5" FOV).

                                                                Hope I don't have to go to an RST-300 (way heavy for my taste, and I w'll need them to release an "E" version, in any case).

                                                                Chen

                                                                    eyecon I too am in Canada, near London Ontario. I have had worm gear mounts and I just got fed up with the huge weight carrying it and then balancing it. I would be looking at a RST135 maybe, as with a harmonic mount I do not have to perfectly balance it all the time as I switch up a lot between my 4 telescope rigs. I think iOptron HAE mounts are just a bit better than ZWO… but maybe not!

                                                                        [unknown] I will probably go with a RST -135 next but I do not need it yet!
                                                                        Is it work going to the 135E instead?

                                                                        • w7ay replied to this.

                                                                          Kevin_A oh didn’t realize you were in Ontario, I’m in Burlington so not too far 🙂

                                                                          Yeah being an iOptron mount user, I looked at the HAE series before pulling the trigger on the AM5 but they seemed a bit too expensive and heavy given their weight capacity…maybe I wasn’t comparing to the right models. Anyway I will try highspeed guiding with metaguide and see if I get better results on the AM5. Based on w7ay experience, the RST seems to be the way to go…for my portable rig use case I’m not sure the price point is justified. I think the RST maybe the way to go if it’s the only mount but at least based on my experience, the older worm gear tech offers a better cost to performance combination.