Where are you observing from?
Location estimated from your device's time zone. Pass times change from one city to the next: set your location for accurate times. It is stored only on this device.
Observing tools: pointing, polar alignment, deep sky
Aim at an object from
Live altitude and azimuth of a celestial object to point an instrument, polar alignment help and Messier objects visible tonight.
- Azimuth
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- Altitude
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Azimuth measured clockwise from true north (east = 90°). Altitude above the horizon, including atmospheric refraction.
Polar alignment of an equatorial mount
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Aim at true north: a compass shows magnetic north, which differs by a few degrees depending on the place (about +2° in France, −9° in South Korea).
In the polar scope, right now
Deep sky tonight
Messier catalogue from OpenNGC (CC BY-SA 4.0). Visible: higher than 20° during full darkness. The suggested instrument is a guide: under a country sky you see far more than in town.
About this tool
What it does
It shows where to point: live altitude and azimuth of the Moon, planets, bright stars, Messier objects, the ISS, Tiangong and Hubble. For polar alignment, it shows where to place Polaris (or Sigma Octantis in the southern hemisphere) in the polar scope. On a phone, viewfinder mode guides the device to the object.
The calculations
Coordinates of date (precession and nutation) and atmospheric refraction: astronomy-engine. Satellites: satellite.js, from their orbital elements. A Messier object counts as visible if it rises above 20° during the dark night. Everything is computed on your device.
The sources
Messier catalogue from OpenNGC (CC BY-SA 4.0), magnitudes completed from SEDS. Orbital elements: CelesTrak. Viewfinder mode reads the phone’s orientation and sends nothing.
Where should Polaris sit in the polar scope?
On the small circle of the reticle, at the hour shown on the dial, like a clock hand. The drawing comes in an inverted view, as in most polar scopes, and a naked-eye view. In the southern hemisphere, it is Sigma Octantis, magnitude 5.4.
Which Messier objects can I see tonight?
Those that pass above 20° altitude during astronomical darkness, sorted by best time, with the suggested instrument and a warning when the Moon is close. To photograph them, see their real size in your sensor's frame.
Will the night be good?
Pointing tells you where to aim; for the Moon, hourly clouds and the planets that are up, see tonight's sky.