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    Moon’s Horns Conundrum
    From: David Pike
    Date: 2021 Feb 19, 01:21 -0800

    Yesterday, Thursday, during our allowed one hour’s ‘lockdown’ exercise walk, both Sun and Moon were visible simultaneously for the first time in many a day.  Unfortunately, having carried my sextant in the car on Tuesday and Wednesday on the off chance of some lunar aiming practice, I forgot to take it with us yesterday. 

    However, I was able to confirm something that’s been worrying me for a while.  We all know that light travels in straight lines, and we read that because of this the perpendicular bisector of the Moon’s horns points towards the Sun.  Except it doesn’t; it tweaks up a touch towards my zenith.  So, I ask myself, should I try and imagine a great circle drawn in the sky from the Moon to the Sun instead; then the perpendicular bisector will point towards the Sun.  In fact, might the same be true for all these imaginary lines in the sky published to help star recognition.  DaveP

       
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