Transit Finder · transit calculator

Exoplanet transit times

Enter your telescope's coordinates and an observing date — the tool works out which exoplanet transits, from a list of bright planets, can be imaged from that place, with start / mid / end times and the altitude above the horizon.

Observing site and date

Latitude (° north positive)

Longitude (° east positive)

Date of the observing night

Minimum altitude above the horizon (°)

Maximum timing uncertainty (min)

Maximum magnitude

Minimum transit depth (mmag)

Maximum transit duration (h)

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Darkness required

The calculator uses a set of 107 transiting exoplanets, extracted and processed from TEPCat — a maintained academic catalogue (Southworth, Keele University) devoted to exactly the parameters observation planning needs (position, magnitude, ephemeris). It covers planets down to about magnitude 14.7, not the full 6,000+ known planets (many of them too faint for any equipment). The list of planets is TEPCat's; the ephemerides are not. Period, epoch, transit depth and both radii are taken from the NASA Exoplanet Archive, from its ps table, each planet's period and epoch taken whole from a single paper that publishes an error on both — the paper whose ephemeris is best determined for today. That error is what the uncertainty column reports, and it grows with every cycle since the reference epoch. Six planets have no such publication anywhere and say so instead of showing a number. For a final check, cross-reference against the NASA Exoplanet Archive ephemeris service or the Exoplanet Transit Database (ETD) (the new portal, VarAstro).

Exoplanet transit times

Observing site and date

The night at a glance

Visible transits