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Simpler Polar Alignment - Will it work?

imaging tripod classic
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#1 mpupeza


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Posted 17 November 2019 - 04:09 PM

I wonder if this will work?

With my old C8+ on a wedge, I adjust the mount properly to center it visually to Polaris. If I  then pick a Southern Star (say Sirius in Feb), can I use the following to Polar Align to NCP.

Center the star Sirius with reticle eyepiece aligning crosshairs with Azimuth and Altitude directions. Let it track for some minutes then re-adjust the errors by adjusting out 1/2 the errors in the Altitude and Azimuth with the mounts base positioning adjustments.Actually move the base azimuth and elevation.

Then re-center Sirius with normal  viewing adjustments and let it track for a while, then re-adjust the mount in alt-az again by 1/2 of the errors with the base mount.

In my mind, I think, with several iterations, it should then be bang on - assuming the motor is at the sidereal rotational rate.

Will this not work?

In mechanics, and electronics, this adjusting out 1/2 the error on multiple iterations is a valid method of accurate tracking.

Again, I think this would be easier than selecting a southern star, adjusting one direction, then picking an eastern star then adjusting the other direction, repeating, etc. My method would not require changing stars.

Any ideas??

Mike P with an old C8+ Byers Drive with Argo Navis DSC......>





#2 Dynan



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Posted 17 November 2019 - 06:01 PM

If you're not perfectly level, one adjustment affects the other. Back and forth...back and forth...tedious, but for a permanent pier, well worth it.


Or just use SharpCap like many of us do.

#3 Phil Sherman

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Posted 18 November 2019 - 12:31 AM

If you pick a star in the SE portion of the sky, then your drift is a combination of both azimuth and altitude errors. With what you propose, how will you seperate out the two components? Drifting a star near the meridian isolates out the azimuth error which you correct for. With the azimuth error corrected, any drift of the E (or W) star must be from altitude errors.


As pointed out in a previous reply, tools like Sharpcap can do polar alignment in one step. They do this by determining the center of rotation of the mount, projected on the sky, then computing the offset from the NCP (or SCP). 

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#4 doolsduck


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Posted 18 November 2019 - 01:30 AM

Is there a reason you won't do traditional drift alignment?  I'm really not much more than a beginner but when I got drift alignment, I realised how simple it is I decided to make a visual model to explain it.  This is a photo of the teaching aid, but it will not mean much without the accompanying videos which can be found here: https://www.youtube....w_as=subscriber

The 15:26sec video called 'polar alignment by the drift method' is the guts of it and is the first one to watch.  I think it is a very easy intuitive way to understand drift alignment. It explains about observational directions to decouple the altitude and azimuth errors and why other areas of the sky do not decouple these errors.

Sorry if you already know how to do drift alignment and are posing your question for another reason.  

Attached Thumbnails

  • drift alignment - 1 (1).jpg

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#5 Jond105


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Posted 18 November 2019 - 03:08 AM

Moved to mounts for better fit

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