Planets

Planets Why Jupiter's Great Red Spot Is the Easiest Planet Feature to Track TypePlanet (gas giant) — a surface feature on Jupiter, the Great Red Spot, a long-lived anticyclonic storm MagJupiter itself ranges roughly from about -2.5 to -1.5 in apparent magnitude, bright enough to be seen with the unaided eye; the Great Red Spot is a low-contrast detail within the planet's disk and needs optical aid to resolve, so it is effectively a small-telescope target ScopeA small telescope is the least equipment that shows the Great Red Spot usefully; a modest aperture with moderate magnification reveals it as a pale oval, while larger apertures and steady air make it easier Jupiter is one of the most rewarding objects for a backyard observer, and the Great Red Spot is the single feature most people want to see. Planets Reading Saturn's Rings: What a Small Telescope Can Actually Show TypePlanet (Saturn) MagTypically around magnitude 0.5 to 1.0, easily visible to the naked eye; its rings require a telescope. ScopeA small telescope (60 mm to 150 mm aperture) is needed to see the rings; larger apertures reveal more detail. Saturn is the crown jewel of the solar system for many amateur astronomers. Planets Mars Opposition Years and Why the Planet Looks Different Each Time TypePlanet (Mars) MagRanges from about magnitude -2.9 at the brightest oppositions down to roughly magnitude +1.8 near solar conjunction; naked-eye whenever it is above the horizon, though small telescopic detail needs a modest instrument ScopeUnaided eye to find and track it; a small telescope is the least gear that shows the polar cap and dark surface markings under steady seeing Mars is the only bright planet whose appearance changes dramatically from one opposition to the next. Planets Spotting Mercury and Venus in Twilight Without Losing Them to the Sun TypePlanet (the two inferior planets, Mercury and Venus) MagVenus ranges roughly magnitude -3 to -5 and is easily naked-eye; Mercury ranges roughly magnitude -2 to +2 and is naked-eye when well placed but often lost in bright twilight ScopeUnaided eye to locate and follow; binoculars or a small telescope to see phases and, for Venus, a featureless disk Mercury and Venus are the two planets that orbit closer to the Sun than Earth does, which is exactly why they are so often described as twilight objects. Planets The Galilean Moons: Watching Jupiter's Four Bright Dots Move Nightly TypeMoons of Jupiter (the four Galilean satellites: Io, Europa, Ganymede, and Callisto) MagThe moons themselves range roughly from magnitude 5 to 6, bright enough for binoculars and often visible in a steady small telescope; Jupiter itself is far brighter, roughly magnitude -2 to -3 depending on the year, and is plainly naked-eye. ScopeBinoculars held steadily or braced will show the moons as tiny points near Jupiter; a small telescope at moderate magnification gives the clearest view of their changing positions. Jupiter is the largest planet in the solar system and one of the most rewarding targets for a backyard observer. Planets Uranus and Neptune: Finding the Planets That Look Like Stars TypePlanet (ice giants Uranus and Neptune) MagUranus about magnitude 5.7–6.0; Neptune about 7.8–8.0. Uranus is marginally naked-eye under very dark skies but usually binocular; Neptune requires binoculars or a small telescope. ScopeUranus: binoculars (7x50 or larger) or a small telescope; Neptune: at least 50mm binoculars, preferably a small telescope at 100x or more. Uranus and Neptune are the two outermost major planets in our solar system, often called ice giants because of their deep atmospheres rich in water, ammonia, and methane. Planets Planet Rotation and the Window When Each One Is Best Placed TypePlanet (Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune) MagMercury -2 to +5, Venus -5 to -3, Mars -3 to +2, Jupiter -3 to -1, Saturn -1 to +1, Uranus +5 to +6, Neptune +7 to +8; Mercury, Venus, Mars, Jupiter, and Saturn are naked-eye, Uranus is binocular, Neptune is telescope-only ScopeUnaided eye for Mercury, Venus, Mars, Jupiter, Saturn; binoculars for Uranus; small telescope for Neptune Planets are the wanderers of the night sky, and each one has a window when it is best placed for evening observing. Planets Why Atmospheric Seeing Ruins a Planet Just When You Want Detail TypePlanet (any of the bright planets visible in amateur telescopes) MagVaries by planet; typically brighter than magnitude 2 and often much brighter, making most planets easily naked-eye objects ScopeUnaided eye to locate; a small telescope (60–100 mm) is enough to show a planetary disk and some detail, though larger apertures help when seeing is steady Atmospheric seeing is the reason a planet that looked crisp in a photograph can turn into a boiling, wobbly blob at the eyepiece.