Penombre: Astro Photo Planner

Penombre plans the shot before you leave the house.

The penumbra is the shadow where a partial eclipse is seen — the app is named after
the thing it computes.

ECLIPSES
• A map of the Moon's shadow, moving: the path, the umbra crossing it, and curves of
how much Sun goes — 20, 70, 90 and 99 per cent
• Tap anywhere on Earth for that spot's contact times, coverage and Sun altitude
• Eclipse day: every phase timed for your exact position, offline
• Eye-safety guidance that changes with what you will actually see from where you are
• The cloud cover that place usually gets in that month, from 20 years of NASA data

THE SKY, DRAWN
• Solar System: the planets in their orbits, each with its own moons
• Earth and Moon, and the shadow that falls between them at an eclipse
• Sky View: the whole horizon laid flat, showing what is up right now
• Sky chart for any date and time — constellations, bright stars, tap for details
• Moon calendar with phases and illumination
• All 109 Messier objects on the chart, drawn with the symbols a star atlas uses —
tap any of them for what it is, how big, how bright and where to point
• The Moon drawn as it will look tonight, tipped the way libration has it: the
features at the edge come and go, and the app says which limb is favoured

METEOR SHOWERS
• The eleven worth going out for, with maxima that land on the right night in any
year, because they are keyed to where the Earth is rather than to a date
• The rate this sky will actually give — corrected for how high the radiant climbs
from where you are and how far the night is from maximum, not the poster figure
• The stretch of the night when the radiant is up, the sky is dark, and the Moon is
out of the way

PLANNING THE SHOT
• Golden hour, blue hour and every twilight stage
• Sun and Moon azimuth on a map, so you know where they will actually be
• Search for when the Sun or Moon sits at a chosen bearing — a full moon setting
exactly behind a landmark
• Tonight: what is visible, when, and how dark it gets

OPTICS
• Depth of field, hyperfocal distance and field of view for your lens and sensor
• Longest exposure before stars trail, by both the 500 rule and NPF — NPF accounts
for aperture and pixel pitch, so a 60 MP body gets an honest answer

ALSO
• 10-day weather with cloud cover, because that is what decides the night
• Saved locations and coordinate conversion (decimal, DMS, UTM, MGRS)
• 17 languages and eleven themes, including a dark orange one for the field

Astronomical calculations work offline. Weather and maps need a connection.
No account, no ads, no tracking.

Astronomical calculations are computed on the device from published algorithms —
nothing is fetched from a server. Weather data comes from MET Norway. Cloud
climatology from NASA POWER (CERES). Maps are © OpenStreetMap contributors.
Deep-sky data from OpenNGC, CC BY-SA 4.0. Constellation figures from d3-celestial.

TAKING IT WITH YOU
• Share the night as a card, or put an eclipse or a shower straight into your calendar
• Where the sky is actually dark: light pollution modelled from satellite data, not a
map of streetlights
• The horizon you really stand under — a ridge or a terrace moves every rise and set
• Pick your camera body once and its pixel pitch comes with it

EYE SAFETY
The eclipse guidance here is information, not protection. What protects your eyes is a solar filter certified to ISO 12312-2 — and during a partial or annular eclipse it never comes off. Computed times can be a minute or two out, so nothing this app shows is a reason to look at the Sun unfiltered.