NavList:

Richard Langley, you wrote:
"If your e-mail program displays some of the text in the previous message
(reproduced below) as a question mark, interpret that to mean the degrees
symbol."

Sorry. That was a bug. It has now been fixed.

For email readers, here is the proper text of that message:
"Interesting, deductive development.

When it comes down to it, virtually everything in celestial mechanics can be expressed using equations, albeit at times with limited precision, and/or extremely long ones. Some of the equations are intuitive, some less so.

The equation of time, E, can be written in equation form as (see Meeus, Chapter 27):

E = L_o - 0.0057183° - alpha + deltaPsi * cos (epsilon)

where:
L_o = sun's mean longitude (given by planetary ephemerides; also representative by an equation)
alpha = apparent right ascension of the sun
deltaPsi = nutation in longitude (given by the nutation theory and a very long equation)
epsilon = obliquity of the ecliptic (can be represented by a polynomial)

The Explanatory Supplement to the Astronomical Almanac, gives a low precision version of the equation of time as

E = -1.915° * sin(G) - 0.020° * sin (2G) + 2.466° * sin(2*lambda) - 0.053° * sin(4*lambda)

(nicely showing the annual and seasonal variations)

where:
G = 357.528° + 35999.050° * T
L = 280.460° + 36000.770° * T
lambda = L + 1.915° * sin(G) + 0.020° * sin(2G)
T = number of Julian centuries from J2000.

Wikipedia also gives some expressions for computing EoT:
http://en.wikipedia.org/wiki/Equation_of_time

-- Richard Langley"

----------------------------------------------------------------
NavList message boards and member settings: www.fer3.com/NavList
Members may optionally receive posts by email.
To cancel email delivery, send a message to NoMail[at]fer3.com
----------------------------------------------------------------