mirror of
https://github.com/acamarata/moon-sighting-dart.git
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70 lines
2 KiB
Markdown
70 lines
2 KiB
Markdown
# Advanced Usage
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## Yallop vs Odeh Criteria
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The package implements two published crescent visibility criteria. Both are returned in `getMoonVisibilityEstimate`:
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```dart
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import 'package:moon_sighting/moon_sighting.dart';
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final vis = getMoonVisibilityEstimate(
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DateTime.utc(2025, 3, 31, 18, 30),
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21.4225, 39.8262,
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);
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print('Yallop zone: ${vis.yallopZone.label}');
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print('Odeh zone: ${vis.odehZone.label}');
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print('Combined: ${vis.zone.label}');
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```
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Yallop and Odeh zones:
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| Zone | Label | Description |
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| --- | --- | --- |
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| A | Easily visible | Visible to naked eye |
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| B | Visible under good conditions | May be visible to naked eye |
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| C | May need optical aid | Visible with binoculars |
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| D | Optical aid and perfect conditions | Telescope only |
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| E | Not visible | Below horizon at sunset |
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| F | Below new moon | Moon sets before sun |
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## Finding the Next New Moon
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```dart
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final newMoon = nearestNewMoon(DateTime.utc(2025, 3, 15));
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print('Next new moon: ${newMoon.toIso8601String()}');
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```
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Pass `next: false` for the previous new moon:
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```dart
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final prev = nearestNewMoon(DateTime.utc(2025, 3, 15), next: false);
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```
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## Monthly Crescent Calendar
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```dart
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import 'package:moon_sighting/moon_sighting.dart';
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void main() {
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// Find when Ramadan crescent might be visible in 2026
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final newMoon = nearestNewMoon(DateTime.utc(2026, 3, 20));
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print('New moon: ${newMoon.toIso8601String()}');
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// Check 3 successive evenings
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for (int d = 1; d <= 3; d++) {
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final check = newMoon.add(Duration(days: d, hours: 18));
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final vis = getMoonVisibilityEstimate(check, 21.4225, 39.8262);
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print('Day $d: ${vis.zone.label}');
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}
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}
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```
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## Accuracy and JS Comparison
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| Aspect | moon_sighting (Dart) | moon-sighting (npm/JS) |
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| --- | --- | --- |
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| Algorithm | Meeus Chapter 47 | JPL DE442S ephemeris |
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| Position accuracy | ~0.3 degrees | Sub-arcminute |
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| Bundle size | Minimal | ~500 KB (ephemeris data) |
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| Best for | Flutter apps, mobile | Server-side, high precision |
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