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Well yes that is correct basically. Having just setup my new mount on the pier i have been through this again. A compass with a rotating bezel helps because you can preset the offset. I am lucky that when i setup the pier i made a mark on the obs wall that corresponds to true south. When facing magnetic south with your compass, true south will be offset 12.3 degrees to your left (or eastern side).
I found that placing a straight piece of timber molding in the dovetail clamp, and using that as a "gun sight" to true south, i could get very close to exact. You only need to be within about 2 degrees for the various plate solving PA tools to dial your mount in exactly. I used Sharpcap's new PA plate solver tool and it is brilliant, takes less than three minutes to get very good PA. Sharpcap is a free download and contains the plates for Northern and Southern hemisphere pole areas in the app so no Net connection required to solve the PA. You don't even need the mount to have power to use it, just release the clutch and rotate RA until it tells you to stop. I am sitting on 9 arc seconds off perfect right now. Which is close enough for any target to be close to my scopes and cameras centre of field of view for tweaking in framing.
And don't forget the mass of your mount ( if it, or the pier, is made of ferris material) will affect the magnetic bearing. Get as far away from any ferris source as possible, including your belt buckle.
Last edited by glend; 26-01-2017 at 06:04 PM.
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