Polar Align Tool

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tmyers
Posts: 46
Joined: Wed Mar 04, 2020 2:49 pm
Location: Dayton, OH, USA

Polar Align Tool

#1

Post by tmyers »

In my opinion SC has the easiest to use Polar Align tool out there. Since SC can control the mount's movement, how hard would it be to have a button that would take the mount from a park position to an east or west position to put the counterweight bar parallel with the ground for the first PA solving. Once solved could simply press park for the 90 degree swing to the second plate solve. At this point you would be Aligned, and parked and ready for a target to slew to.

I have tried to use the mount control for this in SC but 50x Sidereal is just too slow.

I am doing this now, but using CDC with a slew rate of 600 to move the mount. Would love to just do this in SC.

Thoughts?
Tim

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clouzot
Posts: 46
Joined: Thu Aug 08, 2019 11:13 am

Re: Polar Align Tool

#2

Post by clouzot »

I thought about that feature as well, but as long as you have to be close to the mount anyway (in order to fiddle with its alt-az settings), I guess there would be little benefit in automating a 90° slew that is done in 1 second (compared to the time it takes for my AVX to do the same with its lazy motors)
AussieHowie
Posts: 25
Joined: Fri Aug 11, 2017 12:23 am

Re: Polar Align Tool

#3

Post by AussieHowie »

I do PA before turning on the mount. After balancing the OTA, I just release the RA clutch and turn it by hand to each position. Very quick and easy.

When you finish the polar alignment, rotate and lock in the Home position and power up the mount and proceed to 1 or 2 or 3 or whatever star alignment you wish to do for accurate goto. Done.

Also, it does not have to be exactly a 90 degree rotation. If you turn by eye and you didnt rotate quite enough, sharpcap tells you within a couple of seconds that "You have not rotated the mount enough!" Or something like that. Release clutch and turn another bit until you see it say it was successful with the second platesolve and shows you the polar error on the screen. If you go beyond 90 degree's a tad it does not seem to matter. I've never seen an error for that come up.

Also, you can start the PA routine in any position. You can go from 45 degrees on the left to 45 degrees on the right ... or 120 degrees left to 30 degrees left ... whatever starting position you wish ... and rotate counter-clockwise or clockwise ... does not matter.

The rotation is so the routine can work out where your mounts axis of rotation is pointing (its RA bearings and axle). Platesolving tells it where the pole actually is. From those two bits of info it then knows the direction and amount it has to move the polar axis (RA axle) determined from the rotation, to be pointing right at the celestial pole determined from platesolving the stars.
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admin
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Re: Polar Align Tool

#4

Post by admin »

Hi,

In general I think that most people would be happy to use the existing buttons to control the mount - I am a bit concerned though that you seem to only have a maximum speed of 50x sidereal in SharpCap, but higher speeds available in other applications. If that is the case then please can you capture and share a log file (after you've used the mount control a bit) so I can see if I can work out why you don't get the full speed range.

Cheers, Robin
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