ASIAM5 Polar Align

[jerry1]

Hi Robin,

I’ll try that. I’m awaiting a laser pointer bracket due to be delivered later this week. I’ll align it with the scope access at a high power and then attempt to use it for a more accurate polar alignment than what I’ve been able to do by eye. Then I’ll try selecting several objects and see how close plate solving gets to determine if this approach is usable. But truth be told, I’d ultimately like to perform a classical, accurate alignment at some point. Do you think you’ll be able to identify and resolve the issue I’m experiencing? Would it be possible for you to borrow an AM5 to diagnose what is happening and why?

Thanks,

Jerry

[admin]

Hi Jerry,

as far as I can work out from the earlier posts, all you need to do is turn off the 'auto advance' option in the polar alignment tool. That will let you advance through the steps manually and avoid the 'rotation detected' problem.

cheers,

Robin

[jerry1]

Hi Robin,

Well, as mentioned, 'auto advance' was not ticked when I checked it, so I don't know what will happen. However, I will be speaking with someone next week who works at High Point that uses SharpCap with an AM5 mount. I'll let you know what I learn and whether or not it works for me. I will also try to just get a close setting to Polaris as you suggested and then slew to a target and see if plate solving can take me the rest of the way.

It has been cloudy and rainy all week and is forecasted to be the same tomorrow with no clearing until Sunday, so that will likely be my first opportunity to test. This sounds a lot like UK weather, doesn't it? Please don't share it.

Jerry

[admin]

Hi Jerry,

don't knock the UK weather... There was an hour or so last night when I could just about see a hazy full moon through the clouds, before it started raining again

cheers,

Robin

[jerry1]

Ha! Touche.

[jerry1]

Hi Robin, and Happy New Year!

We had a very fine, clear day and evening here, so I was finally able to get outside this evening and see the stars. Over the last few days, I’ve converted from having my laptop directly cabled to run the AM5 mount and camera to placing a mini computer at the tripod and having it do all the work. I’m using my same laptop to remote in wirelessly to the mini-computer to control the mount and camera as well as to receive all images downloaded and saved on the mini – this part is working flawlessly (yes, I’m surprised also).

I’ve reported the foregoing to let you know that I successfully performed a polar alignment and could rotate the R/A axis using SharpCap’s GoTo controls without causing the error reported in the previous posts. Once the error was below one minute on both axes, SharpCap reported a “Good” alignment. I was able to do this whether I used ASTAP or SharpCap’s engine. I then wanted to point the scope to a celestial object to image it and ran into two other problems.

1. For some reason, objects that I could physically see high in the sky, such as Jupiter, M45, M31, etc., were reported by SharpCap’s database as “Below the Horizon” and SharpCap did nothing when I tried to aim the scope toward them – the mount did not move, which makes sense if the target was truly below the horizon. So, suspecting an incorrect setting someplace, I moved to the “Settings” tabs. On the Polar Alignment Settings” tab, instead of using “Estimate automatically from time zone” for Observing Location, I put in my actual Lat and Long coordinates to two decimal points of precision. I also assured that the mini-computer running SharpCap had the proper date and time, which it did. But no matter what I confirmed to be correct, SharpCap refused to believe that celestial objects I could actually see in the sky (and which I also confirmed with Stellarium running on my cell phone in case my vision was failing rapidly… or was it my brain?) It’s as if SharpCap saw my location as being in the southern hemisphere rather than in New England in the U.S.

2. One other issue is that when I checked the polar alignment about 20 minutes later, it seemed to have gotten worse going from errors of R/A and Dec from seconds to minutes. I performed another successful polar alignment, them immediately ran it again to confirm the errors were under one minute, and then proceeded to return to solving the problem of not being able to use the object database to point the scope at a target in the sky. About 30 minutes later, I re-ran the polar alignment routine and it was again 10 – 30 minutes out of alignment, and so, I performed an alignment again. After each successful alignment, I tightened the mount’s locks on the manual R/A and Dec controls, but alignment was never permanent for long.

Have I performed the alignment Incorrectly? If I was aimed at any object other than Polaris, I would have assumed that the mount was not tracking, but Polaris hardly moves because it is so closely aligned with the Earth’s axis. And there was no wind.

I’m sorry for such a long missive, but I wanted to provide enough info on how I had proceeded to help you diagnose the problem, whether with your software, the hardware, or my wetware.

Thanks,

Jerry

[oopfan]

Hi Jerry,

I had similar problems with my German Equatorial mount until I found the culprit. I hadn't thoroughly locked the mount in place after completing polar alignment. There was still some play in the altitude and azimuth adjustment. Also look for possible movement in the tripod. I recommend using the spikes to get a solid grip in the soil.

Good luck,
Brian

[admin]

Hi,

good to hear that you are making progress - even if that leads to new problems... Better than facing the same problem over and over again

For the first problem, the thing to check is the latitude and longitude settings in the AM5 ASCOM driver. Those give the position that SharpCap uses to calculate the altitude and direction of targets in the sky. That's by far the most likely cause (the other is the computer time being off). To check/adjust these, use the 'Setup' button in the telescope control area in SharpCap to access the ASCOM driver setup window.

As for the polar align slipping over time, since you have already checked the tightening of the altitude/azimuth adjustments, movement of the tripod seems the most likely cause. This can just be a case of the tripod legs gradually pressing into soft ground, or could be partly caused by the weight distribution on the tripod changing as you point the telescope to different parts of the sky. I do wonder if this may be more of an issue for harmonic drive mounts - using a mount without a counterweight means that the weight distribution on the tripod legs will change significantly as the mount is moved around, much more than it would for a traditional 'balanced with counterweight' mount.

cheers,

Robin

[oopfan]

Jerry,

I know this isn't a comforting thought but the AM5 has a significant Periodic Error (PE) of +/- 20 arc seconds, so you will need auto-guiding for deep-sky especially narrowband. They claim auto-guiding accuracy of 0.5 to 0.8 arc seconds. Therefore, the post-alignment problems you are experiencing should be mitigated by auto-guiding, that is if there are no sudden movements. That's the beauty of stacking!

Brian

[jerry1]

Robin & Brian,

Thanks to you both for your suggestions! I was on the asphalt driveway last night with rubber feet on the tripod's feet, so the tripod was not sinking nor moving. On these cold nights, I’ve had no problems with heat rising from the driveway affecting the seeing; in the summer, it’s a different story entirely and grass is much better. I did already confirm last night during the testing that the computer's time was correct.

Robin, you could be right that harmonic mounts without counter weights could definitely provide more of a tripod with larger weight distribution shifts. I’ll need to explore that more.

I will also check the settings in the ASCOM driver setup window. I’ll let you know.

Thanks,

Jerry