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97 lines
2.8 KiB
Markdown
97 lines
2.8 KiB
Markdown
# Quick Start
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This guide covers the most common use cases in moon-sighting.
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## Installation
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```bash
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pnpm add moon-sighting
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```
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No peer dependencies. The JPL DE442S ephemeris is bundled.
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## Check crescent visibility for a specific date and location
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```typescript
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import { visibility } from 'moon-sighting';
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const result = visibility({
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date: new Date(2023, 2, 22), // March 22, 2023 — evening of 29 Sha'ban 1444
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lat: 21.3891, // Mecca, Saudi Arabia
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lng: 39.8579,
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elevation: 277, // meters above sea level
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});
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console.log(result.criterion); // 'yallop' (default)
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console.log(result.visible); // true or false
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console.log(result.q); // Yallop q-value
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console.log(result.category); // 'A' through 'F' (Yallop) or 0/1/2 (Odeh)
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```
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## Use the Odeh criterion
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```typescript
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import { visibility } from 'moon-sighting';
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const result = visibility({
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date: new Date(2023, 2, 22),
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lat: 51.5,
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lng: -0.12,
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criterion: 'odeh',
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});
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console.log(result.category); // 0=invisible, 1=optical aid, 2=naked eye
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```
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## Batch: check a range of dates
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```typescript
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import { visibility } from 'moon-sighting';
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const observer = { lat: 40.71, lng: -74.01, elevation: 10 };
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// Check every night for 5 days
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const dates = Array.from({ length: 5 }, (_, i) => {
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const d = new Date(2023, 2, 20);
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d.setDate(d.getDate() + i);
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return d;
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});
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for (const date of dates) {
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const r = visibility({ ...observer, date });
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console.log(`${date.toDateString()}: visible=${r.visible}, q=${r.q?.toFixed(3)}`);
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}
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```
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## CommonJS
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```js
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const { visibility } = require('moon-sighting');
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const result = visibility({
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date: new Date(2023, 2, 22),
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lat: 21.39,
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lng: 39.86,
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});
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console.log(result.visible);
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```
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## Result fields
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| Field | Type | Description |
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| ----------- | --------- | ---------------------------------------------------- |
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| `visible` | `boolean` | Whether the crescent is likely visible |
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| `criterion` | `string` | `'yallop'` or `'odeh'` |
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| `q` | `number` | Yallop q-value (only when criterion is `'yallop'`) |
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| `category` | `string` | Yallop A-F or Odeh 0/1/2 category |
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| `arcl` | `number` | Arc of light (degrees) |
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| `arcv` | `number` | Arc of vision (degrees) |
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| `daz` | `number` | Relative azimuth (degrees) |
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| `w` | `number` | Crescent width (arcminutes) |
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## Next steps
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- [API Reference](API-Reference) for the full input/output schema
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- [Crescent Visibility](Crescent-Visibility) for a detailed explanation of the Yallop and Odeh criteria
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- [Observer Model](Observer-Model) for how observer location affects calculations
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