- At almost all planetarium shows, our projector is used to display ‘The Night Sky.’ We show Juneau’s night sky showing how the sky would look if the sky was clear. We include current and local astronomical happenings. These presentations are informal with audiences asking questions.
- Over the years various teenagers, adults and teachers have been trained to use starball. Volunteers operate the starball and narrate during the presentation. Volunteers incorporate current astronomical events, especially those observable in Juneau, into their presentation.
- The Spitz projector is an analog mechanical optical projection system. It works well for showing the night sky but its capabilities are very limited. It can only show view from earth.
- Our starball turned 50 in 2017. Click here for article on this anniversary.
Art Shaw, Planetarium Director
Spitz Star Projector
The main instrument in the planetarium is the star projector. The Marie Drake Planetarium is equipped with a Spitz Model A3P. The star projector provides a realistic view of the night sky as seen by the naked eye. It projects stars, planets, Sun, and Moon in their correct positions as well as an astronomical grid to illustrate the coordinates used by astronomical charts.
The planetarium cost about $70,000 when it was purchased. It is in working condition despite its age. The star ball is a hollow metal bulb with over 1,400 holes drilled in it. Each hole projects a point of light on the dome to represent a star in the night sky. The brighter star requires a lens to focus the light. The cells that hold the lens over the holes are visible as dark rings on the star projector. Some lens have colored gel to simulate star color. Other holes are covered with small film of images of nebular objects and which collectively project the pattern of the Milky Way Galaxy. The bulb that provides the stars is a 75 watt xenon arc lamp.
The meridian projector projects a line marked off from 0 to 90 degrees from the north point on the horizon, through zenith and down to the southern point on the horizon. The meridian projector allows the planetarium to illustrate how high or low a position(star, planet, etc.) is on the dome from the horizon. The meridian also splits the sky into an eastern and western half. When the sun is directly on the meridian, the time of day of called noon. When the sun is east of the meridian the time of day is called ante meridian(a.m.). When the sun is west of the meridian, the time of day is post meridian (p.m.).
The ecliptic projector displays the path that the sun appears to travel across the sky. This is very useful for illustrating seasonal markers. The coordinate projector displays a partial Earth equatorial coordinate system on the dome. The vertical (similar to longitude) are lines of right ascension. The horizontal lines (latitude) are circles of declination. Astronomical charts use these right ascension and declination marks to track the position of stars, planets, and the Moon in the night sky.
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