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    Re: Sextant Collimation Error
    From: David Pike
    Date: 2020 Jun 25, 16:14 -0700
    Might there be a similarity between looking from the left of ring to right of horizon mirror as opposed to looking down the centre of and not holding the sextant vertical? I’m off
    to try it.  DaveP

    I tested my theory using a Hughes Mate’s sextant with the telescope/sighting tube removed to observe the Sun v the UPVC guttering of my roof.  I’m afraid the test was a failure for the following reasons:

    The Sun was moving too quickly.  I need to try again around local noon. 

    If you want to see the Sun properly, you more or less have to be looking through the centre of the ring.

    With no magnification, it’s that much harder to sit the sun exactly on the UPVC.

    However, as far as I could see, for my sort of observing (i.e. to the nearest minute of arc), so long as the sextant is held vertically, being slightly off the line of sight isn’t a problem, and being a long way off line of sight means you can’t see the Sun.

    I hope we’re talking about the same ring.  I’m talking about the ring the telescope screws into.  The only other ‘ghosts’ I’ve experienced are the ghosts of the Sun you sometimes experience with periscopic sextants. DaveP

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