Celestial Programming: Greg Miller's Astronomy Programming Page

A collection of astronomy related programs, algorithms, tutorials, and data. Most of the code here is public domain, though some of data and/or images my be under other copyright (usually an open source license), details will be given on relevant pages.
Greg Miller (gmiller@gregmiller.net)

Applications

• VSOP-87 Multilang Implementation of VSOP-87 in many different languages.
• Rise and Set Graph Graph showing sun, moon, twilight and other objects' rise and set times.
• Altitude Graph Graph showing the altitude of selected objects over the course of a day for a given location.
• Sky Path Graph showing the path of an object for a given location and day.
• Digital Sextant Use your phone's camera to get a location fix on two stars.

Tutorials

• JPL Ephemeris Format Explains the format of the ASCII and binary files used for the JPL Development Ephemeris, explains how to use the data to compute the positions of the planets and other data stored in them, and has a walkthrough example. Example implementations in JavaScript and other languages are provided.

Snippets

• Julian dates. Snippets regarding Julian date conversions.
• Low Precision Moon Position. Low precision moon algorithm from the Astronomical Almanac. Accuracty .5deg between 1900 and 2100
• Low Precision Sun Position. Low precision algorith from the Astronomical Almanac to return RA/DEC of Sun. Accuracy 1deg from 1950-2050.
• Rise, Set, Transit Times. A simplified implemention of the Rise, Set, Transit algorithm from the book Astronomical Algorithms.
• Moon Position Code to compute the position of the moon using the truncated ELP82 theory in Astronomical Algorithms.
• Moon Phases Implementation from Astronomical Algorithms to compute the dates of phases of the moon.
• Illuminated Fraction of the Moon An implementation of Meuus' aproximation of the illumnated fraction of the Moon's disk.
• Moon Phase Rendering Produces an image showing the phase of the moon.
• Moon Age Computes the approximate age of the moon in days.
• Day of Week Compute the day of the week for a given date, useful for generating calendars.
• Compact Ephemeris A compact and fast ephemeris to generate approximate planet positions. Algorithm from the Explanatory Supplement.
• RA/Dec to Alt/Az Quick approximate conversion to Alt/Az
• Ra/Dec to Alt/Az Test Data A set of about 300 test cases to validate the RA/Dec to Alt/Az implementations.
• Decimal Hours/Deg to Components Converts decimal forms of hours and degrees to hours, minutes, seconds, and degrees to degrees, arcminutes, arcseconds.
• Horizon DistanceCompute various values relating to the distance to the horizon.
• JSON Star Catalog The Hipparcos catalog in JSON format with a simplified number of fields. Links to other common star catalogs.
• Atmospheric Refraction Approximate atmospheric refraction corrections.
• 2000b Nutation An implementation of the IAU 2000b nutation model.
• Equation Of Time A simplified Eqation of Time algorithm.
• Lat/Lon to XYZ Converts the polar coordinates of Latitude and Longitude to Cartisian/Rectangular x, y, z coordinates.
• Stellar Parallax to Distance Convert parallax (in arcseconds) to distance (in parsecs and AU).
• Constellation Stick Figures The stick figures used to represent constellations, taken from Stellarium (GPL License).
• Constellation Center Points The RA/Dec coordinates of the centers of the constellations.
• Rectangular to Polar Convert between rectangular (xyz) and polar (lat/lon or RA/Dec) coordinates.
• Rotation Matricies 2D and 3D rotation matrices.
• Star X, Y, Z Coordinates Compute the rectangular (x, y, z) coordinates of a star from parallax and RA/Dec.
• Alt/Az to Hour Angle/Dec Compute the Hour Angle and Declination from an Alt/Az position.
• GMST Greenwich Mean Sidereal Time.
• Geographic Position A non-rigorous example to convert RA/Dec to a Geographics Position.
• Angle Between Two Ra/Dec Points Computes the angular separation between two points.
• Angle Between Ecliptic and HorizonThe angle between the ecliptic and the local horizion.
• Sky Path Angle Angle between the horizon and the path of an object through the sky.
• Common Star Names A list of common star names and their HIPPARCOS catalog ID.
• Two Star Celestial Fix Compute latitude and longitude using the Alt from two stars.
• Local Solar Time Computes the local solar time for a given longitude.