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    Re: Stick shadows and sundial curves
    From: Adrian F
    Date: 2021 Jun 1, 05:12 -0700

    Hello Tony,

    You said : "If the gnomon (the stick) is at 51.2°N (at the latitude equal to star's declination) the shadow will draw the staight East-West line". 

    I'm afraid I'm having a little difficulty in seeing that. A shadow staying on the straight East-West line seems to imply the star staying at a constant azimuth of 90° or 270°.   Taking the latitude of the stick to be the same as the declination of Vega (38.8°), it seems to me that Vega's azimuth from the stick will vary from 37° (when it rises) to 90°, then from 270° to 323° (when it sets).  Or am I missing something ?

    Thank you for your helpful description of the conic sections as the gnomon moves southwards from the pole, and my apologies if I'm misunderstanding what you were describing regarding a straight line.

    Best wishes,

    Adrian F

       
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