Astro Function Index

Basic Conversions

Normalize Values to be Within Specified Max Value

<float> Keep degrees within 360, hours within 24, etc. Max can be negative.

Day Decimal to Day, Hour, Min and Second Format

<DAY> 1] The first four equations generate one component of Day:Hr:Min:Sec

<HR> 2]

<MIN> 3]

<SEC> 4]

<Mat> Executes all four equations to display Day:Hr:Min:Sec in a formatting matrix.

Day, Hour, Min and Sec to Day Decimal Notation

<DAYDec> Convert input time into a decimal number of days.

<Mat> Input one row matrix (a vector) of above arguments.

Decimal Degrees to Deg, Min and Sec of Arc

<DEG> 1] The first three equations generate one component of Deg:Min:Sec

<MIN> 2]

<SEC> 3]

<Mat> Executes all three equations to display Deg:Min:Sec in a formatting matrix.

Deg, Min and Sec of Arc to Decimal Degrees

<DEGDec> Input DEG, MIN, SEC and get back decimal degrees

<Mat> Input one row matrix (a vector) of above arguments.

Degrees of Arc to Right Ascension and Time Units of Hours, Minutes and Sec

<HR> 1] The first three equations generate one component of Hr:Min:Sec

<MIN> 2]

<SEC> 3]

<Mat> Executes all three equations to display Hr:Min:Sec in a formatting matrix.

Right Ascension and Time Units to Decimal Degrees

<RA> Input HR, MIN, SEC and get RA in decimal format

<Mat> Like above but uses one row matrix (a vector) of above arguments.

Mean Solar Day to Sidereal Day

<DAYDec> Get inverse by dividing Sidereal Day by MEANDay2SIDDay(1).

Date Conversions

Gregorian or Julian Calendar Date to Julian Day Count

<JD> IsGreg flag sets conversion: 1=Gregorian, any other value for Julian

<JD> Gregorian to Julian Day count only

<JD> Gregorian decimal Year to Julian Day. Find JD for mid-year Epoch, i.e.: J1999.5

Julian Day Count to Gregorian or Julian Calendar Date

<MTH> 1] First three return Mth/Day/Year. Conversion type set by IsGreg flag.

<DAYDec> 2] IsGreg flag must be same on all 3: -1 = auto, 0 = Julian, 1 = Gregorian

<YR> 3]

<Mat> Executes all three equations to display Yr:Mn:Dy in a formatting matrix.

<YRDec> Julian day count to decimal year. Find epoch (J1999.23) from JD.

Julian Day Count to Gregorian Calendar Date

<DAYDec> 1] Execute first three to get Mth/Day/Year -- Gregorian calendar only.

<MTH> 2]

<YR> 3]

<Mat> Executes all three equations to display Yr:Mn:Dy in a formatting matrix

Julian Day Count to Julian Centuries from J2000

<JC> Will be negative for dates prior to J2000.

Returns Julian Day Number at 0.0 UT for a Given Julian Day Count

<JD> Returns JD at start of civil day.

Sidereal Time Conversions

Greenwich Mean and Apparent Sidereal Time for Julian Day Date in Degrees of Arc

<DEGDec> IsMean sets conversion type: 1 = GMST to UT, else GAST to UT

<DEGDec> GMST to UT only

<DEGDec> GAST to UT only

Local Mean and Apparent Sidereal Time for Julian Day Date in Degrees of Arc

<DEGDec> IsMean sets conversion type: 1 = LMST at JD, else LAST at JD

<DEGDec> LMST at specified JD and Longitude

<DEGDec> LAST at specified JD and Longitude

UT for Local Mean and Apparent Sidereal Time for Julian Day Date in Degrees of Arc

<DEGDec> IsMean sets conversion type: 1 = LMST, else LAST

<DEGDec> Convert LMST to UT. LONG = 0 yields UT for Greenwich ST

<DEGDec> Convert LAST to UT

<Mat> Handles repeated Sidereal Time in civil day by displaying Hr:Min:Sec in two rows

Precession, Nutations, and Obliquity of the Ecliptic

Precession from Initial Epoch Julian Day Date to Final Epoch Julian Day Date

<RA> In: RA, DEC and JD of initial and final epoch, out: precessed RA (deg)

<DEC> In: RA, DEC and JD of initial and final epoch, out: precessed DEC (deg)

<DEC> Alternate form of (), see text.

Nutation in Longitude and Obliquity of the Ecliptic for a Given Julian Day Date

<SEC> Input is Julian Century (use JCJ2000()), output Nutation in Longitude.

<SEC> Input is Julian Century (use JCJ2000()), output Nutation in Obliquity.

Mean and True Obliquity of the Ecliptic for a Given Julian Day Date

<DEGDec> Input is Julian Century (use JCJ2000()), output Obliquity in degrees.

<DEGDec>

Altitude, Azimuth, Local Hour Angle, Right Ascension and Declination

Altitude and Azimuth of Object to Local Hour Angle of Observer

<DEGDec> See also RA2LHA() version below.

Apparent Right Ascension and Declination from Object's Altitude/Azimuth, Observer's

Latitude/Longitude and UT Time and Julian Day Date

<RA> RA equation

<DEGDec> DEC equation

Right Ascension to Local Hour Angle

<DEGDec> See also AA2LHA() version above.

Ecliptic and Equatorial Coordinate Transformations

Coordinate Transform Between Equatorial and Ecliptic Systems

<DEGDec> Ecliptic Long for true or mean equinox on JD from RA and DEC

<DEGDec> Ecliptic Latitude for true or mean equinox on JD from RA and DEC

<RA> Right Ascension in true or mean equinox on JD from LAT and LONG

<DEGDec> Declination in true or mean equinox on JD from LAT and LONG

Object Coordinates and Phenomena Calculation

Star Data Matrix

Each row contains data on one star. First data row = 1. User can add new star rows.

Star Data Extraction

<string> Star name

<YRDec> Epoch year of star data

<RA> RA of star in decimal degrees

<DEGDec> DEC of star in decimal degrees

<float> Proper motion in arc seconds per year

Planet Data Matrix