This page shows a wide-field image of the night sky from Perth Observatory that is updated at an interval of about 10 minutes. An SBIG ST402 "All Sky Camera" is used to acquire the images. This instrument has a 90° by 140° field of view and provides a wide-field (fish-eye style) image of about 40% the night sky. The sky camera operates between approximately the evening and the following morning's nautical twilight time. This roughly corresponds to 7:00pm and 5:30am Western Australia Standard Time. That is, between 11:00 to 21:30 hours UTC (Co-ordinated Universal Time), and the last image will remain on this web site until the next evening's observing session.
Just an in real optical astronomy, clouds, light pollution, twilight, and moonlight will all effect the quality of the images. If the image quality is poor then return later or on another day. Beware, the Moon is so bright that it saturates the detector and distorts the images (any bright object will create a bright line emanating from it - this is just the overflow of electrons along a row in the CCD camera). However, it is possible to estimate the position of the Moon in the images and thus determine its motion with respect to the background stars. Clear images contain some useful information such as: constellations, star positions, planets, meteors, comets, the orientation of the Milky Way, our galactic neighbours - the Magellanic Clouds or (sometimes) a new nova.
Additionally, a computer generated HA / declination (sky co-ordinates) chart of the sky imaged is provided. Hour angle (HA) is a co-ordinate that indicates the time interval until a celestial object is located at its highest in the sky. It is related to right ascension, the celestial co-ordinate equivalent to longitude on the Earth. Lines of constant HA have an approximately horizontal orientation (especially on the left of the sky image) and are separated by one hour in the chart.
Declination is the equivalent co-ordinate of latitude for celestial objects and lines of constant declination have an approximately vertical orientation on the left and middle of the chart. Northern objects are on the left hand side of the image. Also of note is the South Celestial Pole, the projection of Earth's rotation axis on the sky, located at declination -90° on the right of the image and chart. Notice that the lines of constant declination become more curved in the south and encircle the South Celestial Pole.
To the general public it is thought that stars rise in the east and set in the west. This is partly true - stars originally located on the left to middle of the all sky image (east) will move approximately vertical (to the west) over night. A more correct way to describe the motions of stars is that observers in the Southern Hemisphere will see the stars wheel around the South Celestial Pole (in a clock-wise motion on the all sky image) during the course of the night. This motion is most apparent for stars located close to the Southern Celestial Pole. Note: It is not the stars that are moving in this dramatic fashion - it is an effect produced by the Earth rotating about its axis.
Another way of expressing the motion is that a given star follows the line of constant declination appropriate to its declination (see the sky co-ordinates chart). So stars originally located on the left to middle bottom of the all sky image (east) will move approximately vertically (to the west) over night and so on. Also, one hour elapses between a star's crossing of successive HA lines on the chart.
This camera was purchased with funds from a SEED grant from the Astronomical Society of the Pacific.
Sky Camera Image
Sky Co-ordinates Chart
Other Useful Links
Time lapse movie of the night sky.
Current Perth Observatory weather data.
Current Perth Observatory weather data from the Bureau of Meteorology.
Current Perth region forecast from the Bureau of Meteorology.
Current Perth region weather data from the Bureau of Meteorology.
If you have any comments please them to Perth Observatory.
This page has been accessed times.
