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    Re: Sextant scope out of collimation
    From: Bill Morris
    Date: 2011 Mar 13, 19:30 -0700


    Four and a half degrees is a lot of tilt and should be quite noticeable. Is there a screw loose somewhere in the 'scope mounting? Look for womething like this before attempting to bend the scope mounting. When made of Al alloy, they don't bend, they break, quite suddenly. If all the screws are tight it is better carefully to file a little off the underside of the scope bracket on the sextant until the tilt is corrected. Use a square between the frame and the front lens of the scope to check for squareness.

    Simms gives the error in seconds as 3600(n2.sin 1".tan 1/2w), where n is the tilt in minutes and w is the sextant reading in degrees. For example, a tilt of 60 seconds at a sextant reading of 60 degrees gives an error of 0.6'.

    4.5 degrees tilt would give an error of about 12 minutes at 60 degrees.

    Bill Morris
    New Zealand
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