Planet details

How your telescope shows the sky: binoculars and the naked eye show north up and east left; a refractor or Schmidt-Cassegrain with a star diagonal gives a mirror image (east right); a Newtonian or a straight-through finder turns it upside down (south up, east right). The little N/E arrows on each drawing follow the choice.

Overview lists every planet’s magnitude, size, phase, distance from the Sun, altitude, and rise, highest point and set for the day, and draws the five bright ones side by side at your magnification.

Jupiter draws the disc with its two main belts, the Great Red Spot when it is on the side facing us, the four Galilean moons where they are (labelled I, E, G, C; a ring for a moon in Jupiter’s shadow) and any moon shadows on the disc. Below: each moon’s distance east or west in Jupiter radii and arcminutes; the transits, shadow transits, eclipses and occultations for the next 1–7 nights, each marked visible or not from your place; the central meridian in Systems I, II and III; and the times the Great Red Spot crosses the central meridian.

Saturn draws the globe and the A, B and C rings at their tilt, with Tethys, Dione, Rhea, Titan and Iapetus.

Mars draws the phase, the polar caps and the classical dark markings (Syrtis Major, Mare Acidalium, Solis Lacus and others) for the central meridian; in the close-up they are labelled.

Venus & Mercury show the phase and size, how far from the Sun each is, and a warning when one is close to it.

The Galilean moons use the method in chapter 44 of Jean Meeus’s Astronomical Algorithms (2nd ed., 1998); it reproduces his worked example 44.a to 0.01 Jupiter radius and JPL Horizons' positions for October–November 2026 to about 0.1 radius (2″). Events are timed for the moon’s centre at Jupiter’s edge (or the edge of its shadow, taken as a cylinder, with Jupiter’s flattening); against Horizons' limb-to-limb times they agree within about 3 minutes for Io and Europa and 8 for Ganymede and Callisto, whose discs take longer to cross.

Central meridians use the IAU rotation models (Jupiter Systems I, II and III; Mars; Saturn) with light time, and agree with Horizons within 0.1°.

Saturn’s moons use orbits I fitted to JPL Horizons (SAT441) state vectors for 2015–2040 — a fixed plane, a mean longitude and, for Titan and Iapetus, the eccentricity — within about 1° of longitude (an arcsecond or two) in that span; outside it they drift.

Planet positions, sizes, magnitudes and phases come from the site’s astronomy core (VSOP87).