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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 · Stars: names, positions, distance and colour

starPositionfunction

Where a star is at a moment: its J2000 position carried forward (or back) by its proper motion in a straight line. The frame stays J2000, so precession to the date is not applied: use the result with J2000 coordinates, or convert it to the date with /coordinates. A straight line is good to a fraction of an arc-second for centuries for nearly every star here; it is not good for the few with large motion over millennia.

Import it

import { starPosition } from "@johnmorrisdotca/hoshi-stars";

Definition

function starPosition(star: Pick<Star, "rightAscension" | "declination" | "properMotionRaMas" | "properMotionDecMas">, when?: When): { rightAscension: number; declination: number; }

Parameters

NameTypeDescription
starPick<Star, "rightAscension" | "declination" | "properMotionRaMas" | "properMotionDecMas">

A star, or anything with a J2000 position and a proper motion in milliarcseconds a year (a nearby star from /nearby).

when (optional)When | undefined

The moment as a Date or milliseconds since 1970 (UTC); J2000 when left out.

Returns

{ rightAscension: number; declination: number; }

Right ascension and declination in degrees, J2000 frame, at that moment.

Examples

import { starByName, starPosition } from "@johnmorrisdotca/hoshi-stars";

const now = starPosition(starByName("Arcturus")!, Date.UTC(2026, 10, 7));
console.log(now.declination.toFixed(3));
19.168

What it prints (run when this page was built)

View sourceEdit on GitHubMade from the source of @johnmorrisdotca/hoshi-stars 0.7.0.