moon-sighting-dart/.github/wiki/guides/advanced.md

Advanced Usage

Yallop vs Odeh Criteria

The package implements two published crescent visibility criteria. Both are returned in getMoonVisibilityEstimate:

import 'package:moon_sighting/moon_sighting.dart';

final vis = getMoonVisibilityEstimate(
  DateTime.utc(2025, 3, 31, 18, 30),
  21.4225, 39.8262,
);

print('Yallop zone: ${vis.yallopZone.label}');
print('Odeh zone:   ${vis.odehZone.label}');
print('Combined:    ${vis.zone.label}');

Yallop and Odeh zones:

Zone	Label	Description
A	Easily visible	Visible to naked eye
B	Visible under good conditions	May be visible to naked eye
C	May need optical aid	Visible with binoculars
D	Optical aid and perfect conditions	Telescope only
E	Not visible	Below horizon at sunset
F	Below new moon	Moon sets before sun

Finding the Next New Moon

final newMoon = nearestNewMoon(DateTime.utc(2025, 3, 15));
print('Next new moon: ${newMoon.toIso8601String()}');

Pass next: false for the previous new moon:

final prev = nearestNewMoon(DateTime.utc(2025, 3, 15), next: false);

Monthly Crescent Calendar

import 'package:moon_sighting/moon_sighting.dart';

void main() {
  // Find when Ramadan crescent might be visible in 2026
  final newMoon = nearestNewMoon(DateTime.utc(2026, 3, 20));
  print('New moon: ${newMoon.toIso8601String()}');

  // Check 3 successive evenings
  for (int d = 1; d <= 3; d++) {
    final check = newMoon.add(Duration(days: d, hours: 18));
    final vis = getMoonVisibilityEstimate(check, 21.4225, 39.8262);
    print('Day $d: ${vis.zone.label}');
  }
}

Accuracy and JS Comparison

Aspect	moon_sighting (Dart)	moon-sighting (npm/JS)
Algorithm	Meeus Chapter 47	JPL DE442S ephemeris
Position accuracy	~0.3 degrees	Sub-arcminute
Bundle size	Minimal	~500 KB (ephemeris data)
Best for	Flutter apps, mobile	Server-side, high precision