Comparisons between Two AM5s

Which of these 2 mounts, based on their respective data sheets do you think is most likely to produce the best autoguiding results? As you can see, not only are the maximum and minimum PE quite different, but the close up of the curves are very different as well, one is very jagged and the other quite smooth.

The top one has half the periodic error, so I'd say probably that one.

What about the additional harmonics (the jagged, vs the smoother slopes?

My first reaction is the smoother one but I truly don’t know. Have you tested them both yet?

My first reaction is the smoother one but I truly don’t know. Have you tested them both yet?

Not yet only the one with the higher PE values.

Your images are incredible. I am curious as to what you find with regards to which one is the smoother mount, or if there’s even a difference. Could be someone measured something differently and it just looks worse? Not likely but many things are possible.

I'd say - definatelly the upper mount.
It has less periodic error.

They changed the gear ratio. The older one repeats every 2 degrees, while the newer one is 1.2 degrees. I would say that the older plot is simply smoothed. I don't think you can really compare the two on anything but the amplitude, but the older one has that first harmonic that would incline me toward the newer one.

I agree with John. I think the one graph just looks jagged because they plotted the points and connected them, while the other is smoothed.

Then the reason the top graph looks a bit different is because one is scaled -4 to 4 and the other is -10 to 5.

My mount has higher values, a bit above 20 if memory serves me right, but still guides very well, I've had stable guiding at 0.3 with an OAG. With a guidescope it sits nicely at 0.5 at average unless something is going on in the atmosphere. I never throw subs due to tracking related issues. Unguided it is pretty much unusable though, unless I were to shoot with a wide angle lens probably.

Thanks everyone. I haven't yet tried the new mount, just got it yesterday. I'm getting good guiding results with the first one around .4" to .6" on each axis, but there are moments where the guiding becomes erratic; I've thrown out subs due to this issue. I am trying to pinpoint what the problem is, it may be atmospheric issues, I know once or twice it was a cable snag, so I'd really like to achieve (as we all would!) more consistent guiding. I've asked the weather gods many times to cool it with the turbulence, but they don't listen to me..

I get great guiding most of the time with mine, and then things sometimes go less than perfect for a bit. I’m wondering if it’s phd2 (or it’s implementation on the asiair) that is the culprit. I’ve found that if I catch the guiding going unstable, I can stop and start the plan and everything is fine again. That says to me that it’s not a specific area of the mount that’s the problem.

Sean Mc:
I’ve found that if I catch the guiding going unstable, I can stop and start the plan and everything is fine again.

I've seen the same thing. Every once in a while mine takes off. Are you using an ASIAir?

Yup. For some reason phd2 always wants to pick the crappiest star that nearest to the edge of the frame.

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