The Observatory
Unique Astronomy Instruments
Every calculator on this site does one job well. These do something different: each one is a one-of-a-kind instrument, built once, that turns real calculated sky data into something you can watch move, read from, or print and keep.
Where to start
Pick the question you have tonight
Can I see the Southern Cross, and where?
The Southern Cross Clock answers for your town and hour. From Sydney, Adelaide and Melbourne the whole Cross stays above the horizon all night, every night. Further north, in Perth, Brisbane or Darwin, some or all of it sets each day, and from London it never rises at all.
Which planets are up, and which are close together?
The Wanderers' Lane lines the Sun, Moon and planets up on the one road they all travel, and lists the close meetings coming up, such as the Moon passing a bright planet.
Why does the sky turn the other way up north?
Face south and the stars wheel clockwise around the pole; face north and they turn the other way. The Twin Clocks of Earth show both faces at once, and Earth Clocks follow the same hand around all 24 time zones.
How long ago is long ago?
The Cosmic Calendar turns the age of the universe into one year, so the dinosaurs end on 30 December and every written word fits in the last 12 seconds.
Methodology
Real astronomical data, checked twice
Every position these instruments show — planets, the Moon, sunrise and sunset, conjunctions — comes from Astronomy Engine by Don Cross, the same open-source engine used across CalculationTime’s astronomy pages. We cross-check the results against Jean Meeus’s Astronomical Algorithms, the standard reference text professional ephemeris software is built from, before an instrument is published here.
What that means in practice
Design is ours, positions are not
- The astronomical calculations come from Astronomy Engine, not a guess or an illustration.
- Results are cross-verified against Meeus’s Astronomical Algorithms before publication.
- The visual design, dial layout and print outputs are CalculationTime’s own work.
- Each instrument states its own limitations rather than presenting itself as a professional ephemeris.