John, Ron, all,
When I worked on this I choose 7 date ticks per month in the
following sequence 1,5,10,15,20,25,30 (Feb being the exception tick7 =
28). The URL below is for a PDF file illustrating the analemma marked in
this scheme, zoom in to see the date ticks. The date tick for the first
of the month is drawn in the color of its respective season all others
are drawn in black.
ftp://ftp.gcstudio.com/pub/sundial/analemma.pdf
Not sure about the 1,6,... sequence, perhaps it was chosen to
force the dates of the solstices (typ the 21st) to be included. The leap
year cycle however causes all date ticks to migrate along the analemma
anyhow (some more than others - the standard deviation of the EoT is at
its highest close to the Winter Solstice, i.e., Dec 21) so I can't see
any advantage to trying to force a date in the sequence (esp the 21st).
I liked the 1,5... sequence but I don't think it really matters.
Best,
Luke
