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# Using a 5x24 finderscope for polar alignment

Polar Alignment
2 replies to this topic

### #1 Lito

Lito

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Posted Yesterday, 01:21 PM

I wonder if anyone tried polar alignment using a regular finderscope.

I have a motorized equatorial mount without a polar alignment scope. (EXOS NANO + RA drive motor)

I want to try to polar align using a 5x24 finderscope that I have and plan to attach parallel to the RA axis using a dovetail slot and rings with screws.

I have calculated the AFOV: from a distance (D) of 10m I can see a FOV of 1m diameter

Using this formula: AFOV = 2 X tan-1 (FOV / 2 X D) gives me 5.72 degrees (543' 30")

Polaris is at a declination 89o 21' 09", that is 38' 51" from the celestial pole. or 0.65 degrees.

Inside the finderscope there is a crosshair where I'm thinking of inserting a "reticle".
The aperture in this point is 9.8mm, my "reticle" needs to have a circle with a radius of 1.1mm = (9.8 * 0.65) / 5.72

Anyone has done something similar? Please let me know if my calculations make sense.

Thanks

### #2 rj144

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Posted Yesterday, 04:37 PM

It seems to me your finderscope and mount would need to be aligned dead on, right?  Do you know if that's the case?

### #3 Lito

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Posted Yesterday, 11:39 PM

It seems to me your finderscope and mount would need to be aligned dead on, right?  Do you know if that's the case?

The rings where the finderscope will be attached will have three screws.

The dovetail slot will be attached to the rotating part of the mount, so that a rotation in RA axis will rotate the finderscope.
This will alow me to calibrate the finderscope so that when RA rotating the mount it stays centered on the RA axis of rotation.

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