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Old 31-08-2018, 10:00 AM
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Forge is offline
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Do Alt-Az GoTo mounts require constant realignment?

I've got a Skywatcher 12" GoTo recently and after a month or so of use I've found a minor issue. Before each viewing session I collimate and align it and for a good hour, the GoTo function (i.e. selecting an object and the telescope slewing to it) is almost pinpoint accurate. However after that using the same function, I have to manually use the controller to adjust it by quite a few degrees to get the selected object into the center of the eyepiece.

Is that expected behavior due to the nature of alt-az mounts or does it indicate a problem with the motors or encoders in my specific mount?

Just read the manual and it seems I could use the PAE function to try and correct this, but I've not tried it yet.

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Old 31-08-2018, 12:16 PM
gaseous (Patrick)
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I think you're doing well if you're getting an hour of pinpoint accuracy! I find they can tend to lose a little accuracy over time, and tend to realign after a few hours if the target object is not within a low-power field of view, but if it's out by several degrees, then something may be amiss.
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Old 31-08-2018, 12:56 PM
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The pointing accuracy of gotoís is reduced (Iíve read), with the SW encoders on. I presume that error compounds with time. You could try and see what happens with the encoders off.... I rarely manually locate if Iíve aligned so leave the encoders off mostly.


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Old 31-08-2018, 03:14 PM
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Allan_L (Allan)
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something I posted in another thread:
Originally Posted by Allan_L View Post
Maybe try to check the integrity of the encoders.

Centre an object.
Note the RA Dec from the hand controller.

(This is from the skywatcher manual
Utility > Show Position - This displays the coordinates of the location where the telescope is currently pointed. The coordinates can be displayed in Dec and RA, Alt and Azm, or Ax1 (the angular reading of the elevation) and Ax2 (the azimuth axes of the mount). Use the scroll keys to choose your desired reading

Rotate the mount through 360* then check that the RA Dec reading is the same.

You may also move it back and forth to try to induce any encoder slippage error and return to the original object to check the displayed RA Dec are the same.
The accuracy is always best in the quadrant where your alignment stars are.
I also found the accuracy decreased as the night got colder.
That other thread also had some hints on picking quality alignment stars, just in case you missed it.
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Old 31-08-2018, 07:21 PM
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Thank you all, seems like the scope is doing alright. But I will try your suggestions to do some further testing
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