Orrery

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[[Category:Applications]]
 
[[Category:Applications]]
  
The orrery is a simple application for the openmoko platform which displays the night sky. It is nowhere near as elaborate as, for example Google Sky or xephem. It is intended to be a small application that will have a storage footprint comparable to a ringtone, or one of the games bundled with the
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The orrery is a simple open-source application for the openmoko platform which displays the night sky. It is nowhere near as elaborate as, for example Google Sky or xephem. It is intended to be a small application that will have a storage footprint comparable to a ringtone, or one of the games bundled with the
 
openmoko rootfs. It requires no network connection, but does use the GPS information, by querying gpsd.
 
openmoko rootfs. It requires no network connection, but does use the GPS information, by querying gpsd.
  

Revision as of 02:43, 26 March 2008

In progress: This article or section documents one or more features whose implementation are in progress.

The orrery is a simple open-source application for the openmoko platform which displays the night sky. It is nowhere near as elaborate as, for example Google Sky or xephem. It is intended to be a small application that will have a storage footprint comparable to a ringtone, or one of the games bundled with the openmoko rootfs. It requires no network connection, but does use the GPS information, by querying gpsd.

Orrery Screen Grab 1

The image above shows the default display - all stars visible to the unaided eye, with colors for the brightest ones. It's displayed with a Transverse Mercator projection (similar to Norton's Star Atlas) which works well with the VGA aspect ratio. It's a conformal transformation, so the constellations have about the right shapes. The sun, moon and planets are plotted, and the moon is shown with the proper phase.

The view can be panned around the sky by tapping the green arrows at the bottom, or the green azimuth values.

Orrery Screen Grab 2

If one taps the main display area, the program toggles into constellation mode, as shown above. In addition to constellation names and figures, the celestial equator (light yellow), ecliptic (red) and galactic plane (blue-green) are shown. Solar system objects are shown symbolically (see Mars in the above image).

The star database was extracted from the Hipparcos catalog. To ease the computational load, the coordinates are not precessed or nutated before being displayed. Currently, planetary ephemerides (from JPL Horizons) are used, but I hope to which to using orbital elements soon, because that will substantially reduce the required storage space.

I have not yet gotten this packaged for proper distribution, but I would be extremely happy to send the files to anyone who wants to have this program. I'd of course be happiest if you made suggestions about how the program could be improved. I can be contacted at orrery.moko@gmail.com.

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In progress: This article or section documents one or more features whose implementation are in progress.

The orrery is a simple application for the openmoko platform which displays the night sky. It is nowhere near as elaborate as, for example Google Sky or xephem. It is intended to be a small application that will have a storage footprint comparable to a ringtone, or one of the games bundled with the openmoko rootfs. It requires no network connection, but does use the GPS information, by querying gpsd.

Orrery Screen Grab 1

The image above shows the default display - all stars visible to the unaided eye, with colors for the brightest ones. It's displayed with a Transverse Mercator projection (similar to Norton's Star Atlas) which works well with the VGA aspect ratio. It's a conformal transformation, so the constellations have about the right shapes. The sun, moon and planets are plotted, and the moon is shown with the proper phase.

The view can be panned around the sky by tapping the green arrows at the bottom, or the green azimuth values.

Orrery Screen Grab 2

If one taps the main display area, the program toggles into constellation mode, as shown above. In addition to constellation names and figures, the celestial equator (light yellow), ecliptic (red) and galactic plane (blue-green) are shown. Solar system objects are shown symbolically (see Mars in the above image).

The star database was extracted from the Hipparcos catalog. To ease the computational load, the coordinates are not precessed or nutated before being displayed. Currently, planetary ephemerides (from JPL Horizons) are used, but I hope to which to using orbital elements soon, because that will substantially reduce the required storage space.

I have not yet gotten this packaged for proper distribution, but I would be extremely happy to send the files to anyone who wants to have this program. I'd of course be happiest if you made suggestions about how the program could be improved. I can be contacted at orrery.moko@gmail.com.