This single-file solution provides a high-performance, responsive, and aesthetically premium application for astrophotography calculations. It adheres to all constraints: no external storage, zero dependencies other than CDNs, and a clean, light-mode interface. ```html Free Rule of 500 Astrophotography Exposure Calculator

Astrophotography Exposure Calculator

Calculate maximum shutter speed to prevent star trailing.

300 is recommended for high-resolution sensors.

Max Shutter Speed
12.5s

With this setup, keep your shutter open for no longer than 12.5 seconds to ensure sharp, circular stars.