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Bill Osuch - Random geek notes

Way back in the dark ages (1985 or so) there was a book title Astronomy With Your Personal Computer by Peter Duffett-Smith. This book provided BASIC routines for various astonomical calculations: date/time conversions, planetary location, eclipse information, etc. Some of the calculations would be handy for some mobile apps I'm working on, so I decided to look into converting the code to C#.

Just looking at a few lines of the sample programs in the book, it becomes quickly obvious that simply converting the code line-by-line is not a good idea - if nothing else, the precision of the calculations is suspect, and many of the old BASIC commands are just inefficient. Plus, I'm not trying to infringe on any copyrights here!

So, my goal here will be to simply duplicate the purpose of each of the major subroutines in the book in C#. I've listed them below, and as future blog posts are written I'll come back and add the appropriate link.

Subroutine Description
DEFAULT default value input routine
No need to convert this one...
YESNO 'Y' or 'N' input routine
Yeah, skip this one too...
MINSEC converts between decimal hours/degrees and minutes/seconds form
JULDAY calendar date to Julian day number since 1900 January 0.5
CALDAY Julian day number since 1900 January 0.5 to calendar date
TIME converts between local civil and sidereal times
EQHOR converts between equatorial and horizon coordinates
HRANG converts between right ascension and hour angle
OBLIQ calculates the value of the obliquity of the ecliptic
NUTAT finds corrections for natation in longitude and obliquity
EQECL converts between equatorial and ecliptic coordinates
EQGAL converts between equatorial and galactic coordinates
GENCON converts between any of the coordinate systems
Gotta love that subroutine name!
PRCESS1 approximate precession of equatorial coordinates
PRCESS2 rigorous precession of equatorial coordinates
PARALLX converts between geocentric and apparent position
REFRACT calculates the effect of atmospheric refraction
RISET finds the circumstances of rising and setting
ANOMALY solves Kepler's equation for elliptical motion
SUN finds the ecliptic coordinates of the Sun
SUNRS finds the circumstances of sunrise and sunset
PELMENT returns the orbital elements of the major planets
PLANS finds the position of a planet
MOON finds the position and parallax of the Moon
MOONRS finds the circumstances of moonrise and moonset
MOONNF finds the times of new and full moon
ECLIPSE finds the circumstances of lunar and solar eclipses
DISPLAY displays an eclipse in graphical form
ELOSC finds positions from osculating elliptical elements
RELEM converts elliptic orbital elements from one epoch to another
PCOMET finds the position of a comet from parabolic elements
PFIT finds parabolic elements from observations
EFIT finds elliptical elements from observations

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Posted on Monday, October 3, 2011 11:06 AM C# , Astronomy | Back to top


Comments on this post: Updating the book Astronomy With Your Personal Computer

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