But would anyone claim to measure declination to seconds of arc? Still seems a puzzle to me!
Regards, John ----- Original Message ----- From: "Frank King" <[EMAIL PROTECTED]> To: "fer de vries" <[EMAIL PROTECTED]> Cc: "sundial" <[EMAIL PROTECTED]> Sent: Saturday, April 21, 2007 10:28 PM Subject: Re: strange longitude > >> I looked with Google ... and I got a picture of the dial... > >> It is an east declining sundial for local suntime and I >> think the value is the declination of the dial. > > That thought occurred to me too. In which case PL might be a > slightly unusual use of the navigator's term Position Line? > > Strictly, a Position Line is the local arc of the circle > centred on the sub-solar point that passes through the > position you happen to be at. The plane of the dial > stands on this arc when the outward normal to the plane > is in the same direction as the sun. > > That is a good moment for measuring the declination > of the dial which gives it some relevance. > > Maybe this is stretching the idea of a Position Line > too far!! > > Frank King > Cambridge U.K. > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
