Re: Playing during an eclipse

Arthur J. O'Dwyer wrote:
To clarify, for those readers who are as slow-witted as I was: The game
doesn't care about eclipses at all. But lunar eclipses always happen
during full moons, and solar eclipses always happen during new moons.

(The game doesn't care about eclipses because they're too complicated
to predict in advance, or too irregular in occurrence, or something. The
algorithm for computing the phase of the moon is surprisingly simple,
though.)

AFAICT it is an adaptation of part of the Easter formula, though it has been adjusted to make it more suitable for computers, using modular integer arithmetic instead of lookup tables. The moon it works with does not exactly follow the real moon but an approximation to it based on a perfectly circular orbit of constant speed. Occasionally it will be off by a day or two (which is why Easter seems to be almost two weeks off from its "proper" date in some years). Also, AFAICT, the SOL and LUN corrections are absent, so Nethack will gradually drift out of alignment with the real phase of the moon over the next century or two.

(YANI: A switch for nethack that makes it say what time it thinks it is and all time-related info instead or starting the game. Good for public servers. Or maybe a simple wrapper round hacklib.c would do.)

--
Simon Richard Clarkstone:
s.r.cl?rkst?n?@durham.ac.uk/s?m?n.cl?rkst?n?@hotmail.com
Scheme guy says: (> Scheme Haskell)
Haskell guy says: (> Scheme) Haskell
.

Relevant Pages

  • Re: astronomy/moon accuracy in BCE years, customizing formulas
    ... astronomical calculations to answer some questions as I develop some ... Is it possible to accurately calculate moon data (phase, age, azimuth, ... altitude, rise/set, perigeee, apogee, zenith angle, eclipses, and so ... How difficult is it to get accurate calculations in the arctic ...
    (sci.astro)
  • Re: Playing during an eclipse
    ... that's a full moon condition. ... doesn't care about eclipses at all. ... (The game doesn't care about eclipses because they're too complicated ...
    (rec.games.roguelike.nethack)
  • Re: Anglican Addresses - sources?
    ... Passover is celebrated at full moon. ... in fact solar eclipses only occur at the time of a full ... Erm no, no confusion, solar eclipses only occur at the time of a full ... between the Earth and the Sun and so facing the observer. ...
    (uk.misc)
  • Re: Eclipse during a full moon?
    ... Solar eclipses are ALWAYS during a new moon. ... eclipses both of the sun and the moon. ... He didn't mean that Juliet was the sun that gives all life, ...
    (talk.origins)
  • Re: The Heavenly Match: A Cosmic Oddity
    ... Some say that Stonhenge is a rough predictor of solar eclipses. ... The eclipse is not always total, since the moon moves in an elliptical ...
    (talk.origins)