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77 lines
1.9 KiB
Markdown
77 lines
1.9 KiB
Markdown
# Quick Start
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Five minutes from install to solar position.
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## Install
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```sh
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npm install nrel-spa
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```
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## Basic usage
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```js
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import { getSpa } from 'nrel-spa';
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const result = getSpa(
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new Date('2025-06-21T12:00:00Z'),
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40.7128, // latitude
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-74.0060, // longitude
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-4, // UTC offset in hours (EDT)
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);
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console.log(result.zenith); // solar zenith angle in degrees
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console.log(result.azimuth); // solar azimuth in degrees
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console.log(result.sunrise); // fractional hours, e.g. 5.42
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console.log(result.sunset); // fractional hours, e.g. 20.58
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console.log(result.solarNoon); // fractional hours, e.g. 13.00
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```
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`getSpa` is synchronous. There is no initialization step, no WASM loading, no async overhead.
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## Formatted output
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```js
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import { calcSpa } from 'nrel-spa';
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const result = calcSpa(
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new Date('2025-06-21T12:00:00Z'),
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40.7128,
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-74.0060,
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-4,
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);
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console.log(result.sunrise); // "05:25:12"
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console.log(result.sunset); // "20:34:47"
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console.log(result.solarNoon); // "12:59:58"
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```
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## Custom zenith angles (twilight)
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```js
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import { getSpa } from 'nrel-spa';
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const civil = getSpa(date, lat, lon, tz, {}, [96]); // civil twilight
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const nautical = getSpa(date, lat, lon, tz, {}, [102]); // nautical twilight
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const astro = getSpa(date, lat, lon, tz, {}, [108]); // astronomical twilight
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console.log(civil.customAngles[0].sunrise); // civil dawn
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console.log(nautical.customAngles[0].sunrise); // nautical dawn
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```
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## Options
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```js
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const result = getSpa(date, lat, lon, tz, {
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elevation: 100, // metres above sea level
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pressure: 1013.25, // millibars
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temperature: 15, // Celsius
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delta_t: 67, // ΔT in seconds
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});
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```
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## Next steps
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- [API Reference](../API-Reference) — full function signatures and return types
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- [Architecture](../Architecture) — module structure and algorithm notes
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- [Advanced Guide](advanced) — twilight, batch calculations, polar scenarios
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