Solar Eclipse Visibility

Combine apparent Sun and Moon diameters with their centre separation to gauge how deep a solar eclipse will be from your observing site. The result reports the percentage of the solar disc obscured and a practical viewing window to plan photography or outreach.

Apparent angular diameter of the Sun in arcminutes for your location and time.
Apparent angular diameter of the Moon in arcminutes at maximum eclipse.
Angular separation between the Sun and Moon centres at maximum eclipse (arcminutes).
Duration from first through last contact visible at your site, in minutes (defaults to 180).

Examples

  • Partial eclipse geometry with a 31.6′ Sun, 30.4′ Moon, and 10.2′ centre separation ⇒ 56.62% obscuration
  • Near-total geometry with a 32.0′ Sun, 34.5′ Moon, and 2.0′ separation ⇒ 98.18% obscuration

FAQ

How do I find Sun and Moon diameters?

Consult ephemeris tools such as JPL Horizons, Stellarium, or trusted planetarium software—they list apparent diameters for any observing site and time.

Does this tell me exact contact times?

No. It summarises depth and viewing duration. Use dedicated eclipse prediction tools for precise first through fourth contact times.

Why might my observed obscuration differ slightly?

Atmospheric refraction, uneven lunar limb topography, and local horizon obstructions can shift the apparent overlap—treat the output as a mid-event estimate.

Additional Information

  • Geometry assumes circular apparent discs and ignores limb darkening, which only slightly alters deep-total values.
  • Classification depends on the diameter ratio and overlap, flagging whether totality or an annular ring is expected.
  • Event span is clamped between 30 minutes and 4 hours to reflect realistic contact timelines for most sites.
  • The viewing window boosts coverage by 25% to account for pre- and post-maximum interest, then caps at the full contact span.

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