Date & Time
Stargazing Planner - Planet Visibility Calculator
Check when Mercury, Venus, Mars, Jupiter, and Saturn are visible in the sky. Uses simplified orbital mechanics to predict planet elongation and visibility.
Near greatest elongation - best visibility in evening sky. 68° from Sun
Near greatest elongation - best visibility in evening sky. 90° from Sun
Low in the morning sky. Elongation: 59°
Low in the evening sky. Elongation: 45°
Low in the morning sky. Elongation: 58°
Sky map (approximate elongation from sun)
Dot size = relative brightness. Not-visible planets are omitted.
Simplified model using mean orbital elements. For precise positions, use Stellarium or similar.
Light pollution: the Bortle scale
The Bortle Dark-Sky Scale (1–9) measures sky brightness at a location. Lower is darker.
| Class | Description | Milky Way visibility |
|---|---|---|
| 1 | Truly dark sky (remote desert, ocean) | Clearly defined, casts faint shadows |
| 2–3 | Typical genuinely dark site | Clearly visible, complex structure |
| 4–5 | Rural/suburban transition | Milky Way visible but washed out |
| 6–7 | Suburban sky | Faintly visible near zenith only |
| 8–9 | City sky | Invisible; only brightest stars visible |
Best conditions
- New moon or thin crescent moon (less sky glow)
- Low humidity and no clouds
- Good "seeing" (atmospheric stability) - important for planets and double stars
- Allow 20–30 minutes for eyes to dark-adapt; avoid white light
Seasonal highlights (Northern Hemisphere)
- Winter: Orion and its surroundings dominate the sky - the Orion Nebula (M42), Betelgeuse, Rigel, and the Pleiades (Messier 45) open cluster are best viewed December through February.
- Spring: the Virgo Cluster of galaxies becomes well-placed. Leo is prominent with several bright galaxies.
- Summer: the Milky Way core is best visible in the southern sky on July–August nights. Scorpius rides low on the horizon with the galactic center behind it. The Summer Triangle (Vega, Deneb, Altair) is high overhead.
- Autumn: the Andromeda Galaxy (M31) - the nearest large galaxy, 2.5 million light-years away - is directly overhead in October. The Great Square of Pegasus frames it.
Equipment guide
- Naked eye: star patterns, bright planets, satellites, meteor showers. Best for wide-field experiences and learning the sky. No equipment needed.
- Binoculars (7×50 or 10×50): excellent for open clusters, the Milky Way, and the Moon's surface. The wider field of view makes them more beginner-friendly than a telescope. Also portable.
- Telescope: required for planetary detail (Saturn's rings, Jupiter's moons, Mars polar caps), globular clusters, and resolving galaxies. Minimum aperture of 70–80mm for satisfying planetary views; 6–8 inch reflectors for deep-sky objects.
Moon phase effect on darkness
A full moon raises the effective Bortle class of your observing site by approximately 2–3 classes, effectively turning a Class 4 rural site into a Class 6–7 suburban sky for faint object viewing. The full moon also washes out anything within 40–50° of it. Plan deep-sky sessions for the week centered on new moon. Lunar observing and planetary viewing are unaffected by moonlight.
Averted vision technique
The center of your retina (the fovea) is packed with color-sensing cones but has relatively few rod cells, which detect faint light. Looking slightly to the side of a faint object rather than directly at it places its image on the more rod-dense part of the retina, making it appear brighter. This technique - called averted vision - can reveal objects too faint to see when looking directly.