# Celestial Programming: Greg Miller's Astronomy Programming Page

### Greg Miller (gmiller@gregmiller.net)

### Applications

### Tutorials

- JPL Ephemeris Format Explains the format of the ASCII 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.
- Algorithm for Rise, Set, and 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.
- 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.