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Polar alignment tolerance

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#1 SpaceWatcher

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Posted 25 January 2014 - 01:32 PM

Hi all,

I know polar alignment accuracy is important for tracking with a GEM, but how close is acceptable?

If a goto is not quite on (1-2 degrees?) will the mount (I'm considering an AVX) track on both axies to maintain tracking?

Is there any coorelation between how far off the alignment and how frequently declination corrections will be needed by the mount?

I am sure the tolerances are different for visual and AP, but I wanted to get an idea of hte level of correction necessary relative to the distance of the alignment from the pole.

Thanks for the help!

Mike

#2 WarmWeatherGuy

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Posted 25 January 2014 - 03:44 PM

If a goto is not quite on (1-2 degrees?) will the mount (I'm considering an AVX) track on both axies to maintain tracking?


I am pretty sure that while tracking the DEC axis is turned off, only the R.A. axis is running. Due to polar misalignment the object will drift north or south. You can use the up/down arrow buttons to put the object back in the center or you can redo the goto. Note that you can have excellent gotos even though your polar alignment is way off. Having good gotos doesn't tell you anything about how accurate your polar alignment is. You can see the polar alignment error in the Align menu that you get to by pushing the top left button on your NexStar hand controller.




Is there any coorelation between how far off the alignment and how frequently declination corrections will be needed by the mount?


Yes. Watch this video and it will make sense to you. The audio is horrible so turn on captions to see what he is saying.

#3 rmollise

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Posted 25 January 2014 - 03:52 PM

Hi all,

I know polar alignment accuracy is important for tracking with a GEM, but how close is acceptable?

If a goto is not quite on (1-2 degrees?) will the mount (I'm considering an AVX) track on both axies to maintain tracking?

Is there any coorelation between how far off the alignment and how frequently declination corrections will be needed by the mount?

I am sure the tolerances are different for visual and AP, but I wanted to get an idea of hte level of correction necessary relative to the distance of the alignment from the pole.

Thanks for the help!

Mike


Depends on you. For visual, just plunking the mount down pointed north is usually good enough.

Go-to and tracking are two entirely different things. Polar misalignment doesn't affect go-to accuracy with the VX.

If you mean "polar alignment," yes, the farther from the pole you are, the more the mount will drift in declination. Again, polar and go-to alignment are two separate issues.

The VX does NOT track in declination.

;)

#4 schluterdude

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Posted 25 January 2014 - 08:04 PM

Only RA runs while tracking. If both axis ran, polar alignment wouldn't be needed.

Tracking is only done in one axis for mechanical accuracy. The more axis involved (in any movement), the more chance for error.






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