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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 · Map projections for sky charts

unprojectfunction

The sky position under a point of the chart: the inverse of project, with the same options.

Import it

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

Definition

function unproject(kind: Projection, point: MapPoint, options: ProjectionOptions): SkyPoint | undefined

Parameters

NameTypeDescription
kind"stereographic" | "orthographic" | "gnomonic" | "equidistant" | "equirectangular" | "mollweide" | "hammer"

The projection.

pointMapPoint

A point of the chart, in the same units and convention as project gives.

optionsProjectionOptions

The same options that drew the chart.

Returns

SkyPoint | undefined

Right ascension (0 up to 360) and declination in degrees, or undefined when the point is outside the map: beyond the edge of the orthographic disc, the equidistant disc (radius pi times scale), the Mollweide and Hammer ovals, or the equirectangular rectangle.

Examples

import { project, unproject } from "@johnmorrisdotca/hoshi-stars/projection";

const options = { centre: { rightAscension: 279.2, declination: 38.8 }, scale: 200 };
const spot = project("orthographic", { rightAscension: 290, declination: 45 }, options)!;
console.log(unproject("orthographic", spot, options)); // { rightAscension: 290, declination: 45 }, to rounding
{ rightAscension: 290, declination: 45.00000000000001 }

What it prints (run when this page was built)

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