The following symbol set should be used in dialling equations wherever possible. In computer programs and spreadsheets, where Greek symbols cannot be used, the capitalised version should be used instead. The sign conventions and reference points for the various parameters are given in the main glossary. |

Preferred symbol |
Alternativesymbols |
Meaning |
Dimensions |

(a) Co-ordinates on the celestial sphere, etc. | |||

RA | Right Ascension of a celestial body | angle or time | |

DELTA, DEC | declination of the Sun (or other celestial body) | angle | |

ELON | ecliptic longitude of a celestial body | angle | |

ELAT | ecliptic latitude of a celestial body | angle | |

EPS | obliquity of the ecliptic | angle | |

e_{c} |
EC | eccentricity of the Earth’s orbit | dimensionless |

s | S | Sun’s semi-diameter | angle |

(b) Observer’s local co-ordinates | |||

LON | longitude (terrestrial) (positive west of Greenwich) | angle | |

PHI, Lat | latitude of a place | angle | |

h | HA | hour angle (p.m. hours give positive angles) | angle |

A | AZ | azimuth of the sun (clockwise from S) | angle |

a | ALT | altitude of the sun | angle |

z | ZD | zenith distance | angle |

PA | parallactic angle | angle | |

(c) Sundial parameters | |||

d | DEC | declination of a wall (E negative, W positive) | angle |

i | INC | inclination of the dial plate (horiz. to back of dial) | angle |

v | V | angle between noon line and angle of greatest slope for a declining, inclining dial | angle |

SH | SH | style height or angle from dial plane (note unusual use of “height”) | angle |

SD | SD | sub-style angle from noon line | angle |

DL | DL | difference in longitude | angle |

X | HLA | hour line angle from noon line (positive for pm) | angle |

N | NH | nodus height above dial plate (or length of vertical style) | distance |

(d) Time related | |||

E | EoT | Equation of Time (as a time) | time |

E_{a} |
EoTA | Equation of Time (as an equivalent hour angle) | angle |

t | T | time (subscript shows which system) | time |

LAT | LAT or L.A.T. | Local Apparent Time | time |

LMT | LMT | Local Mean Time (LAT corrected for EoT) | time |

ST | ST | Standard Time (LMT corrected for longitude) | time |

TDT | TDT | Terrestrial Dynamic Time | time |

TZ | TZ | Time Zone number (integer) | dimensionless |

t_{sr}, t_{ss} |
TSR, TSS | times of sunrise and sunset | time |

JD | JD | the Julian Day number | days |

SDT | sidereal time | time | |

ST | ST | standard time | time |

ET | ET | ephemeris time (obsolete) | time |

UT or UTC | UT | Universal Time (Co-ordinated) | time |

GMT | GMT | Greenwich Mean Time | time |

DST | DST | Daylight Saving Time | time |

BST | BST | British Summer Time | time |

(e) Co-ordinate systems | |||

(x, y) |
X, Y | cartesian co-ordinates of a point on the dial plane w.r.t. the origin. Optionally, (x, y, 0) in 3-D | length, length |

R, THETA | polar co-ordinates of a point on a dial plane w.r.t. the origin | length, angle | |

hec | HEC | hectemoros angle | angle |

hor | HOR | horarius angle | angle |

(f) Miscellaneous | |||

MU | refractive index | dimensionless | |

R_{o} |
R0 | angle of atmospheric refraction | angle |

T | TEMP | temperature | Kelvin |

Notes: is traditionally used for both terrestrial and ecliptic longitudes. In the rare cases where this could cause confusion, they should be denoted _{t} and _{e}, respectively. |