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Hoshi Stars星

The stars you can see without a telescope, with names, colours and distances; the 88 constellations with their lines and boundaries; the Messier objects; and seven map projections to draw them on.

Hoshi is the Japanese word 星 for a star. About the name

Contents

Reference · /chart

SkyBodytype

One body to draw over the stars: a planet, the Moon, a dwarf planet. Everything is given by the page (this package computes no positions).

phase is the lit fraction of the disc, 0 (new, dark) to 1 (full, or a planet with no visible phase). A body drawn as a disc (the Moon, always; any other whose disc is 4 pixels wide or more) shows it: the lit part is a crescent below 0.5 and gibbous above. brightLimb says on which side it is lit.

Import it

import type { SkyBody } from "@johnmorrisdotca/hoshi-stars/chart";

Definition

interface SkyBody {
    id: string;
    names: SkyBodyNames;
    ra: number;
    dec: number;
    magnitude: number;
    phase: number;
    brightLimb?: number | undefined;
    size?: number | undefined;
}

Members

NameTypeDescription
idstring

What a pick says it was (hoshi-pick's id). The Moon is moon: it is drawn as a disc with its phase, a little larger than its true size so that the phase can be seen.

namesSkyBodyNames

The name written beside it, in English and in Japanese; the chart's language chooses.

ranumber

Where, in degrees: right ascension 0 to 360 and declination -90 to 90 (J2000, the frame the stars are in). A body whose number is not finite is not drawn.

decnumber
magnitudenumber

The apparent visual magnitude (the Moon's is about -12.7 when full, Venus's about -4, Mars's 1.8 at its faintest). A body fainter than the chart's magnitude setting (5), made fainter by 2.5 for each tenfold of zoom as a telescope does, is left out.

phasenumber

The lit fraction of the disc, 0 to 1. A value outside it is held to it; one that is not a number counts as 1 (full).

brightLimb (optional)number | undefined

Where the lit side is: the position angle of the middle of the bright limb in degrees, measured from celestial north through east (the Almanac's convention; 90 is east, the side of the next star to rise). When left out, the lit side is the right of the chart.

size (optional)number | undefined

The apparent diameter in arc-seconds. Left out, the body is a dot sized by its magnitude like a star; given, the disc is drawn at its true size where that is bigger than the dot.

Examples

import type { SkyBody } from "@johnmorrisdotca/hoshi-stars/chart";

const moon: SkyBody = { id: "moon", names: { en: "Moon", ja: "月" }, ra: 83.2, dec: 21.4, magnitude: -11.7, phase: 0.25, brightLimb: 250, size: 1860 };
console.log(moon.names.en, moon.phase);
// Moon 0.25
Moon 0.25

What it prints (run when this page was built)

View sourceEdit on GitHubMade from the source of @johnmorrisdotca/hoshi-stars 0.47.0.