-----Original Message----- From: Mac Oglesby <[EMAIL PROTECTED]> To: Roger Bailey <[EMAIL PROTECTED]> Cc: [email protected] <[email protected]> Date: Wednesday, September 01, 1999 8:04 Subject: Re: Italian Hours
> > >September 1, 1999 > >Hello Roger, > >I wonder what it would take to make it a sundial showing hours until dark. >That is, how would the time of "dark" (relative to sunset) be determined? > <snip> Nice idea Mac! Perhaps Roger could design the dial to show time remaining until (1) sunset (2) civil twilight (3) nautical twilight, and (4) astronomical twilight I've always been confused about when the three twilights begin and end. My best guess is that the order is: (1) Astronomical twilight begins (altitude = -18 deg) (2) Nautical twilight begins (altitude = -12 deg) (3) Civil twilight begins (altitude = -6 deg) (4) Sunrise (altitude = 0 deg) (5) Sunset (altitude = 0 deg) (6) Civil twilight ends (altitude = -6 deg) (7) Nautical twilight ends (altitude = -12 deg) (8) Astronomical twilight ends (altitude = -18 deg) If this is not right, would someone please set me straight and "end" my confusion. (My "Confusion twilight" "began" quite some time ago :) Charlles
