I have had an AM5 for abount a month now, and I've had it out quite a few times.
While I like how smooth the mount and its Alt/Az controls operate, I must say that it is the most difficult of my half-dozen mounts to polar align. With my experience with different brands and designs, I generally take 90 seconds to 4 minutes to polar-align to less than 30 arcsec (the former being iOptron CEM120s or 40s with iPolar, the latter one being with NINA's 3-point polar alignment with a Celestron CGX mount). For comparison, the fastest I seem to be able to get through it with the AM5 is 12-20 minutes.
I completely understand the fact that I don't need to obsess over the error if it's under a handful of arc minutes given my focal length. The problem is that even when I am happy with my PA, I re-run the routine again and ASIAir will tell me it's 10, 20, 30, even 40 arc minutes off. So, even when I spend 20 minutes, it seems for naught.
I have spent hours with various techniques:
- Do an initial PA run with all-tight clutches.
- Loosen the clutches until there's still noticeable friction.
- Adjust Az until it's within 5 arcmin, then slightly tighten the clutches.
- Adjust Az more, until it's within 1 arcmin and then tighten the clutches more.
- Adjust Alt until it's within 5 arcmin, then slightly tighten the clutches.
- Adjust Alt more, until it's within 1 arcmin and then tighten the clutches more.
- The problem, as everyone seems to experience, is that ANY adjustment of either ALT or AZ can affect the other axis by several arc minutes or more. So, I keep iterating through this.
- When I get both axes close to an arcmin, I try to final-tighten the clutches. Of course, this completely throws off everything and I end up being 5, 8, 10 arcmin off.
- Yes, I PA without crossing the meridian. I've tried sticking near the NCP, or pointing near Zenith or the celestial equator.
- Yes, I've replaced the rubber feet with the steel grass pegs (on a giant concrete slab).
I have tried many variations of these techniques, such as doing ALT first or getting everything to 1' before trying to do the initial clutch tighten. I've spent hours in the discussion forums reading people trying the same approaches. Nothing seems to work appreciably better than what I normally do. Part of me thinks there is just a mechanical issue with how the mount interfaces with the tripod and with the Alt/Az controls. And hey, smaller-pitch threads would help with those finer adjustments!
Now, I'm posting this to the ASI Mount forum but much of my difficulty may be the polar alignment tool of the ASIAir. I say this because I can set up my mount, run PA, not even approach the mount, run PA a second time and miraculously be off by 10 or 20 arcmin from what it said the first time. The ASIAir PA tool seems highly inconsistent and unreliable to me. I should have hooked up one of my MiniPCs running NINA and PHD to see how long the effort takes with this mount, to prove or disprove the ASIAirs's contribution to my problem. I could also then see the drift-obtained PA error to see if the ASIAir was close.
Now, I am running a 12 pound payload without a counterweight on the ZWO CF tripod. So, there may be some flexure as the mount slews, affecting PA. But, if that were the only cause, I'd see similar results if I re-ran the PA routine with the identical start point without adjusting anything. I do not. It always varies, by more than what would be acceptable for long exposures.
That was long, whew! I'm not sure what I'm expecting from the community, but there it is. My opinion, based on the very simple observation that this mount is more difficult to PA than any of my others and is far less consistent across PA runs.
