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    Re: Lunar observation engraving c.1871
    From: Peter Monta
    Date: 2022 Jun 28, 18:40 +0000
    Here's my (doubtless incomplete) list.

    • octant rather than sextant
    • missing index arm
    • if it's a telescope: optical axis not aligned to horizon mirror
    • if it's a peep sight: unit magnification not enough for lunars
    • eye too far away from telescope eyepiece or peep sight
    • star shining through the moon
    • chosen star has low sensitivity to lunar motion
    • upper dotted line goes to center of moon (or perhaps some random point on the limb) rather than the limb's nearest point to the star
    • upper dotted line should intersect the sextant at the index mirror
    • lower dotted line should intersect the sextant at the horizon mirror
    • odd-looking back-sight assembly
    • deck watch not shown
    • lunar elongation is very low, making for a challenging (or impossible) sight

    Cheers,
    Peter

       
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