Reference
Your sky: altitude and azimuth for a place and a moment
import { … } from "@johnmorrisdotca/hoshi-stars/sky";Exports
| Name | Kind | What it is |
|---|---|---|
greenwichSiderealTime | function | The Greenwich mean sidereal time: how far the Earth has turned against the stars, as the right ascension on the meridian of Greenwich, in degrees (Meeus 12.4, the IAU 1982 expression). |
horizontal | function | Where a star (or any J2000 position) stands in the sky of a place on Earth at a moment: its altitude above the horizon and azimuth from north through east. |
Horizontal | type | Where a star or a planet is in your sky: degrees above the horizon (negative below it) and degrees round from north through east. |
horizontalFrom | function | Where a star stands in the sky of a place on ANOTHER planet: the sky turns about that planet's pole (the IAU WGCCRE pole and prime meridian, passed in as spin), so the star is rotated into the planet's own equatorial frame, its hour angle is the prime meridian plus the observer's east longitude minus its right ascension there, and the horizon formulas are the same as for Earth. |
HorizontalOptions | type | How to read the position and whether to bend the light. |
isAboveHorizon | function | Whether a position is above the horizon of a place at a moment (altitude greater than 0). |
localSiderealTime | function | The local mean sidereal time: the right ascension that is on your meridian, due south or north of you, in degrees. |
Observer | type | Where you stand on Earth, in degrees. |
PlanetSpin | type | The spin of another planet, as the IAU WGCCRE gives it: where its north pole points, and how far its prime meridian has turned. |
precess | function | A J2000 position carried to the mean equator and equinox of a date: the precession of the Earth's axis (Meeus chapter 21, the rigorous method with the IAU 1976 constants, good for a few centuries either side of 2000 to far under an arc-second). |
SkyPoint | type | A point on the celestial sphere, in degrees. |