AM5N erratic guiding

Bill H

Hi all- I have been encountering erratic guiding with my AM5N. This seemed to occur just after the recent ASIAIR updates, but may be coincidental. Guiding is stable for a period of time, and then I start to see spikes. When I got the mount in July, guiding was excellent. In an email with the support staff, I was sent instructions to adjust belt tension. I opened the mount, and belt tension was fine. However, I noticed when slewing that the belt would migrate to the upper or lower flange of the driven pulley, depending on skew direction. I assume this means the motor and driven pulleys are not coaxial. I also noticed that the upper flange on the driven pulley does not look concentric.

Is this behavior normal, or could it be causing my issues?

Kevin_A

Bill H it could also be a bad belt. Make sure it is not just the belt. Look for any wobble in the stepper drive gear teeth or the SWG teeth. If they both run true then the belt may have been too tight and has broken a few internal strands from over stress, making the belt crooked slightly in 1 place at 1 side. Like belt hernia!
My mount too is very similar in function even with good belt tension. It will guide crappy for half an hour when first started up then run sub 0.45” for 2 hours then go off the rails again or it will run great all night! It is like flipping a coin. Not sure if the update did any foul or harm or just add more grief elsewhere? Make sure it is the gears, but most likely it is the weakest link.. a belt!

MrAstro

Also,,
I noticed that seeing is a major factor that affected guiding, in addition of different factors that each one has a slight affect on the guiding too.
In the same session, always things changed, like seeing, temperature, humidity, location of the target in the sky, gears cycle inside the mount.. etc.

elpajare

Guiding varies throughout the night continuously. High clouds that we don't see, passing medium and low clouds, wind, humidity changes...etc.
The guide star size (HfD) should always remain between 3 and 5 for good guiding. Use 1 second exposures and vary the gain to stay within these HfD parameters.

Kevin_A

Seeing is definitely more a factor when guiding at 0.5-1.0s but multistar guiding really helps with reducing the effects of that. But, I too have also seen my guiding go off the rails where the atmosphere was very stable and constant too using a $1000 guide scope and top end guide camera.
I am not sure if it is how Asiair implements guiding but my mount usually guides better with crappy star centroids vs very good tight stars, and sometimes better in hazy skies. This is the first mount I have ever seen this happen with. With old school worm gears, people would often over tighten their belts and they had similar bad guiding and upon opening up their mounts they would find belts that had partial torn internal fiberglass reinforcement strands from being too tight and their belts were misshapen. Recently I had 4 nights of clear skies and it guided fabulous on two, fair on one and horrible on one and the skies and sky and wind data was all equal. Before the recent update my guiding was not as good but a constant 0.7rms with just a few spikes here and there. My AM5 is the original 432s period first gen which erratic guiding seems to be quite normal and maybe that is why they changed gears to 288s period without warning. It is what it is and I will be getting a new mount in the near future anyways. It also maybe time to change back to phd2 and stop enduring the weekly asiair updates that screw things up…

MrAstro

I have very consistent guiding when the sky is good, RMS 0.40-0.65 average,
At bad seeing or dusts ( as my region famous with dusts ) I got RMS 0.70-0.80 average.
Those values are always appeared according to that specific sky situations.
And that why I consider seeing is the most critical factor, All that in case of I have good control of other factor, like cable management, tripod stability, multi star, polar alignment, calibration etc..
NOW if seeing was perfect and one or more of other factors is not prober controlled do not expect you will have a good guiding.. EACH factor has its own impact at different amount.
I use 1 sec , 50mm FL200mm Guide scope, PHD2, Agg. about 60-70 on both axis, heavy stable tripod, nearly balanced Dec.,