Stargazing Site Visibility Forecast Overlay

WHAT IT DOES This script scans weather and astronomy forecast pages—Clear Outside, Meteoblue, Astrospheric, and others—for visibility conditions including cloud cover, transparency, seeing, darkness, wind, and humidity. It displays a floating overlay showing a comprehensive stargazing forecast with an overall visibility score from 0-100%, color-coded conditions (green for good, yellow for fair, orange for poor, red for bad), and a summary of key metrics. The panel shows cloud cover percentage, seeing and transparency ratings (0-5 scale), darkness percentage, wind speed, humidity, and additional details like temperature and moon phase. Users can set custom thresholds for "good" visibility, export forecast data as CSV, and store viewing location preferences. A history section tracks previous forecasts for the domain. WHERE IT RUNS Works on any weather or astronomy forecast page—Clear Outside, Meteoblue, Astrospheric, 7Timer, SkippySky, or any site displaying cloud cover, seeing, transparency, and darkness data. The script scans page content for numeric values and ratings, making it compatible with most stargazing forecast platforms. HOW TO USE The panel appears automatically when you visit a forecast page. It detects visibility conditions and calculates an overall score. The score card shows the percentage and color-coded status. The metrics grid shows cloud cover, transparency, seeing, darkness, wind, and humidity. Additional details like temperature and moon phase appear when available. The history section shows your last 10 forecast snapshots with scores. Set custom "Good" and "Fair" thresholds using the input fields—the color coding adjusts accordingly. Click "Refresh Forecast" to rescan the page for updated data. Export all forecast history as CSV for trend analysis. Use "Clear History" to reset stored snapshots for the current domain. The panel automatically saves a snapshot each time you visit, building a history of visibility conditions. TECHNICAL MECHANISM: MULTI-PASS FORECAST EXTRACTION WITH WEIGHTED SCORE CALCULATION The script uses a comprehensive detection strategy. First, it scans the page text for cloud cover patterns using regex for percentages, transparency and seeing using numeric values (0-5 scale), darkness using percentages, and wind/humidity using numeric patterns. Second, it scans tables for label-value pairs, checking for "Cloud Cover," "Transparency," "Seeing," "Darkness," "Wind," and "Humidity" labels and extracting adjacent values. Third, it scans elements with class names matching metric keywords (cloud, transparency, seeing, darkness, wind, humidity) and extracts numeric content. The visibility score is calculated using a weighted formula: cloud cover contributes up to 50% penalty (lower cloud = better), transparency and seeing contribute 30% and 40% respectively, darkness contributes 20%, wind penalizes up to 30 points for high wind, and humidity penalizes above 50%. The final score is capped at 100 and rounded. Color coding uses user-configurable thresholds: good (≥70 by default), fair (50-69), poor (30-49), bad (