Too many years ago now to be worth counting, I decided it would be interesting, albeit not tremendously useful, to write a planetarium program. The original motivation was that I couldn't find any free applications that conveniently plotted the positions of the planets on the sky at consecutive intervals (days months or years) with the dates beside them. This is a handy feature if you want to quickly know when a planet will appear in the vicinity of certain other objects in the sky.

After two or more years I finally implemented the original feature I wanted in my planetarium, but not after first adding hosts of other features I thought would be useful or necessary; in short, my small project turned into a full-featured planetarium application. Since then I've been using this program almost exclusively for my amateur astronomy needs and it has suited my needs quite nicely.

I finally got around to producing a deploy-worthy version for free distribution which can be downloaded by following the link at the bottom of the page. The application will work in any Windows OS but has only been tested in OS's from Win98 onward. I have also provided the Borland C++ Builder 6.0 source code for those who feel like hacking in their own features. Good luck reading the code; I had some silly habits when I wrote this application years ago. Enjoy!

Summary of the features of the SkyAtlas planetarium (Windows application)


You have the choice of spherical, cylindrical, Lambert and Mercator projections. My favorite for everyday usel is the Lambert projection. Mercator is handy for really wide field, all-sky views.


  • SAO star catalogue - This catalogue contains stars down to 10th magnitude or so; about 350,000 total.
  • RC3 galaxies - The third reference catalogue of bright galaxies, 23,000 records.
  • ARP peculiar galaxies
  • Lynd and Barnard dark nebulae
  • Messier - But of course!
  • RNGC & IC - ...Can't do without these!


Draws the standard "western" constellation line figures as well as the IAU defined constellation boundaries and labels.

Astrometry and Coordinates

All coordinates are precessed to the nearest Julian day at which the sky is being viewed. If proper motions are available then these are used to correct star positions. Planet positions are accurate to 30 arcseconds over the next 180 years (based on a JPL model from the late 1970's). The coordinates displayed when mousing over the sky can be either equatorial, horizon (altitude-azimuth), galactic or with respect to the ecliptic.


Planet paths can be displayed, with or without labels. The planets and their moons are rendered in a separate window showing the surface features and limb darkening of the planet at the current epoch.


Includes a catalogue of locations on earth to quickly enter longitude and latitude (this is basically a list of airports). This catalogue can be customized by the user. Note, any new location used does not have the correct time zone stored; the user must enter this value.


  • Creates simple maps for printing out.
  • Has a quick pop-up legend for the object symbols used.
  • Colours the stars according to spectral type.
  • Hide or show objects below the horizon.
  • Translates Dreyer codes used in the RNGC catalogue into plain English.
  • Catalogues include commonly used names for the objects.
  • Object search engine.
  • Images for all catalogued objects. If an image is not provided then you can add your own by copying it to the "Images" subdirectory of your SkyAtlas installation path. Note that the distribution does not contain the images I use personally because of copyright restrictions. I built my own image library from the Anglo-Australian Telescope (AAT), the SEDS Messier Catalogue website and some Hubble Heritage Team images.

Usage hints

  • Right clicking displays information for the closest object to the mouse cursor.
  • Left click and drag on the chart to change the view or use the scroll bars along the bottom and right edges.
  • Make sure you enter the number of hours from Greenwich of your location in the location dialogue.
  • Works best on screens with resolutions of at least 800x600.
  • When you have the object information dialog open, clicking on highlight causes the object to be circled on the map so it can be easily found later. Favorite objects can be added to a list in the information dialog for quick retrieval but these are not saved between sessions.
  • Almost every feature can be toggled on or off in the "View" menu.

Peculiarities (i.e. unwanted features or bugs)

Everything is drawn with Borland C++ Builder wrappers around Windows GDI commands so the drawing is slow. On post 2000 machines this is basically not an issue. Getting constellation figure lines to terminate correctly at the edge of the screen was a real pain, so you will occasionally see a stray line drawn across the screen when the constellation figures are turned on.

Things to do when I'm bored (i.e. it will never happen)

  • The galaxies really need an elliptical profile to show their extent on the sky... might get to it one of these days.
  • Include a tool to add additional satelites of earth and the sun.
  • Write some help files!
  • Rewrite the graphics engine to use OpenGL.


The compiled application and source can be freely used or modified for non-commercial purposes as long as credit to the author is given in its use.


Borland C++ Builder 6.0 source code for release version 1.00 : (14,131 kB)

Windows installation package : (18,962 kB)

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More of my projects: Marc Baril's home page