I emphasize that saying that each third of an ecliptic-month is 10 degrees
is not an approximation. An ecliptic-month is defined as exactly 1/3 of an
astronomical- quarter…1/3 by ecliptic-longitude, not by time or days.
An astronomical-quarter is the ecliptic interval between a solstice & an
equin
BTW, I like sundials that tell the ecliptic-months, Aries thru Pisces.
…for which one would need the Solar declinations for the beginning of each
ecliptic-month, & preferably also for some fractions of each
ecliptic-month, such as 1/3 & 2/3.
On Fri, Oct 14, 2022 at 10:16 PM Michael Ossipoff
wro
-- Forwarded message -
From: Michael Ossipoff
Date: Fri, Oct 14, 2022 at 10:16 PM
Subject: Re: How to turn ecliptic longitude into solar declination?
To: Steve Lelievre
Or you could just use the ecliptic longitude, reckoned as usual from the
Vernal Equinox…multiply its sine b
Multiply the sine of ecliptic longitude (reckoned forward or backwards from
the nearest equinox) by the sine of 23.438 or whatever the current
obliquity’s exact value is).
Take the inverse sine of the result.
On Fri, Oct 14, 2022 at 4:57 PM Steve Lelievre <
steve.lelievre.can...@gmail.com> wrote:
Hi,
For a little project I did today, I needed the day's solar declination
for the start, one third gone, and two-thirds gone, of each zodiacal
month (i.e. approximately the 1st, 11th and 21st days of the zodiacal
months).
I treated each of the required dates as a multiple of 10 degrees of
