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A Complete Guide to the Solar System and the Night Sky
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public Observing fromLocation: Greenwich, United Kingdom edit_location_alt
SunriseRise: 6:42  
clear_day Transit: 12:10  
SunsetSet: 17:40
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This site aims to provide accurate real time data and finder charts for the most interesting Solar System objects. Currently we are tracking 453 objects, including comets, planets, asteroids and spacecrafts.


The ephemeris provided by this site (which include coordinates, distances from Earth and Sun, estimated magnitude and, for comets, time to perihelion) are obtained from the JPL Horizons service. In order to compute real time data, we are using interpolation of the Horizons sampled data, which provides a quite good accuracy. It you need very accurate and lates up-do-date data, please use the Horizons service directly.

Finder Charts and Catalogs

Our Finder Charts (see example) are created using the Digitized Sky Survey imagery. For each object, we acquire a 60'x40' DSS image in the red channel and we add overlays to represent the observed object, plus informative labels about the stars and deep sky objects represented in the chart. The position of the overlays is dynamic, this means that in case of fast moving objects (e.g. fast moving comets) it should be possible to see the live movement of the object on the chart.

We are using the following astronomical catalogs to show information about represented objects:

  • Hipparcos Catalogue: contains information about 117934 bright stars. We use green labels for information from this catalogue
  • Tycho 2 Catalogue: contains information about 2430468 stars. We use blue labels for information from this catalogue
  • PGC 2003 Catalogue: contains information about 983261 galaxies. We use red labels for information from this catalogue
  • GSC 2.3 Catalogue: an all-sky catalog of approximately 2 billion stars and galaxies containing positions, magnitudes,colors and proper motions complete to a minimum of V=18. We are using grey labels when showing information from this catalog


Comet Observation Data

  • We acknowledge COBS, the Comet Observation Database for the usage of recent comet observation data, in particular the recently observed comet magnitude and coma diameter.

HTML5 Sky Maps and 3D orbit diagrams

  • The constellation lines used in the ephemeris computation HTML5 sky charts have been created by Dan Burton as part of his Star Chart project.
  • The HTML5 sky charts and orbit diagrams have been developed using the three.js javascript 3D library.
  • The astronomy.js library by Don Cross is used to compute approximate position of the Solar System objects given their keplerian elements.



Please use one of the following ways to send any feedback for improvement, questions or suggestions:

  • Write to:
  • Use the Feedback Form

You are free to use and share content from this site, like data and screenshots, provided you cite and link the source.

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Since its launch in 2013, this site has been developed and maintained by Iacopo Sassarini, as a personal project to bring together interests in astronomy and coding.