🔭 Astronomy & Space Tools

How much of a star's light the atmosphere is stealing at any altitude, in which band, and how long you have before it is not worth imaging. Airmass climbs steeply below about 25°.

Explore rotating habitats and short-arm centrifuges. Calculate floor gravity, rotation period, rim speed, target RPM, head-to-foot gravity gradient and Coriolis acceleration while moving.

Convert cabin pressure and gas fractions into oxygen, carbon-dioxide, water-vapour and inert-gas partial pressures. Compare oxygen availability across mixed-pressure habitat concepts.

Turn crew size and mission duration into a first-pass launch mass for water, food, oxygen and daily supplies. Every per-person assumption is editable, including water recovery and contingency.

Turn range into one-way light time, round-trip conversation delay, file-transfer finish time and free-space path loss. Useful for planning when a crew cannot wait for real-time help from Earth.

Check a spacewalk timeline against oxygen, carbon-dioxide removal, battery and cooling endurance. The tightest resource sets the planning margin while overhead reveals usable task time.

Estimate the two burns, coast time, departure phase angle and repeat opportunity for a coplanar Hohmann transfer between circular orbits around the same central body.

Model a controlled push across a cabin: impulse sets speed, distance sets coast time, and the same momentum must be removed at the destination. Include cargo and recoil from a free-floating support.

Combine prior dose, mission duration, a measured or assumed daily rate, shielding reduction and one-off events. Compare the total with a value you choose without pretending that one universal caree...

Apply Tsiolkovsky’s rocket equation to wet mass, dry mass and specific impulse. Check ideal delta-v capability, propellant needed for a manoeuvre, reserve allowance and remaining mass.

Balance solar generation, sunlit and eclipse loads, orbital timing and usable battery depth. See both the eclipse survival margin and whether each orbit finishes with an energy surplus.

Event horizon radius, surface gravity, Hawking temperature, evaporation time and the tidal force at the horizon for any mass. Compares stellar and supermassive black holes side by side.

Psychological research shows that experiencing awe instantly silences self-critical rumination and triggers spontaneous gratitude. Traverse 40 orders of magnitude through the cosmos, feed your worr...

Turn a Sky Quality Meter reading, a Bortle class or a naked-eye limiting magnitude into the others, and see what each sky condition is worth for deep-sky work. Useful for choosing a site before you...

How long a single subframe needs to be before the target signal clears the read and sky noise, and how many of them you need to stack. Includes the f-ratio squared penalty that makes fast scopes so...

Two tidal bulges, not one. The Moon (and a weaker Sun) stretch Earth into a prolate spheroid; a port rotates through both bulges and sees two highs a day. Align Moon and Sun for spring tide; put th...

Interactive star map — explore 30 major constellations, click stars for names and facts

Animated orrery of our solar system — watch planets orbit in real time, click for detailed facts

Convert right ascension and declination into altitude and azimuth for your latitude and local sidereal time — or go the other way. Tells you whether a target is up, where to point, and when it tran...

Phase, illumination fraction, age and a drawn disc for any date and time — plus the next new and full Moons and how much moonlight is washing out the sky. Runs entirely offline.

Charles Messier was hunting comets. These 110 smudges kept fooling him, so he numbered them (1771–81). The hall is now a rite of passage for amateur astronomers. Magnitudes are visual; distances ar...

Why do phases exist, and why are eclipses so rare? Spin the Moon around Earth (its real orbital inclination is 5.14°) and rotate the line of nodes — the place where the Moon's tilted orbit crosses ...

Fly a probe through a real gravity field. Set your starting speed and direction, hit Launch, and watch the trajectory obey Newton's law (a = −GM/r², integrated semi-implicitly). Get a circle at cir...

Build your own ringed world: gas giants with racing storms, lava planets with glowing cracks, tilted Keplerian rings where inner particles genuinely orbit faster, and up to three moons. Every world...

Land on every world like an astronaut with a telescope: a real 3D sphere you can spin, tilt and zoom, textured per planet from real features — Mercury's craters, Venus's hidden iron-peaked clouds, ...

Put in a redshift and get the recession velocity, Hubble distance, light-travel time and the wavelength a known spectral line is shifted to. Distinguishes Doppler motion from cosmological expansion.

Drag to orbit a 3D Sun–Earth model and discover why seasons happen. It is not distance — it is the 23.4° tilt of Earth's axis, which changes the Sun's noon altitude and the length of the day.

A real 3D orrery of the whole solar system with true orbital mechanics — Kepler's equation is solved every frame, so Mercury visibly speeds up at perihelion and retrograde Halley's comet dives insi...

See the planets side by side to true relative scale, compare them by distance, day length, gravity or moons — and find out what you'd weigh on each. All the figures are built in; nothing is fetched...

A sundial only works at the latitude it was cut for, which is why the garden-centre ones are decorative rather than accurate. Give it your latitude and this lays out the hour lines properly — the a...

A whole year of light for any point on Earth, computed offline with the NOAA solar equations: sunrise, sunset, solar noon, the three twilights, golden hour, the compass bearing the sun rises on, ho...

How precisely your secondary and primary need to be aligned for the images you want, and what a star test tells you about the error you actually have. Based on the wavefront tolerance criteria from...

Work out what an eyepiece actually gives you on a given telescope: magnification, exit pupil, true field of view and the practical limits. Covers Barlows and finds your maximum useful power.

What can your aperture actually split, and how faint can it go? Computes the Dawes and Rayleigh limits, the theoretical limiting magnitude, and the doubles and deep-sky targets that fall within reach.

Every body is drawn at its real size and real distance — no compression. Start at the Earth–Moon system (the Moon's orbit is 60 Earth radii across!) and zoom out through the inner planets, the gian...