An astrolabe illustrates how the sky looks at any given time of day and throughout the year. This is accomplished by drawing the sky (star patterns) on the astrolabe with moveable parts to adjust for the date and time. The traditional sky map astrolabe allowed people to locate celestial objects in the sky similar to how a place is located using a map. A mariner’s astrolabe is different in that it was used to measure the height or altitude of the Sun or of a star above the horizon. The altitude of a star is the angular height above the horizontal from 0 to 90°. Mariners needed to measure the altitude of the Sun or stars in the sky in order to determine their position. Knowing the altitude of the Sun at noon or of the pole star at night told them their latitude (their distance, north or south, from the equator.
The azimuth of a star is its angular position from north, measured clockwise. For example a star located directly to the north of Earth has an azimuth of 0°, while a star directly to the east has an azimuth of 90° and a star to the northwest has an azimuth of 315°.
Curriculum Connection: Grade 6 Space, Grade 9 Astronomy
To help find your way around the night sky, Skymaps.com makes available for free each month The Evening Sky Map. It is a 2-page monthly guide to the night skies of the northern and southern hemispheres. Each issue contains a detailed sky map, a monthly sky calendar, and a descriptive list of the best objects to see with binoculars, a telescope, or using just your eyes. The font size on the printout is about a nine, but still readable for my aging eyes.
Great magazines like SkyNews (Canadian) and Astronomy (American) offer an equal amount of information as Skymaps and with interesting articles that befit magazines of this caliber.
Educators can make printed handouts for non-commercial educational use.
For educators and students who want a current sky map for free, this is one valuable resource.
Some testimonials about Skymaps:
“Your sky maps are great — visually attractive, easy to use and information dense. Great for unaided eye and casual stargazing, a fine introduction to astronomy, especially for younger night sky explorers. Great job! Thanks!”
— Kevin M. Ahern (Massachusetts, USA)
“Great maps. I am so happy to have found you. Thank you. It helps so much to have a monthly map, for planets and such-like and rediscovering childhood constellations with my child.”
— Monty Drake (British Columbia, Canada)
By Stan Taylor
Stan Taylor is a retired elementary school teacher. He currently does science workshops for Scientists in School and is a member of the Crucible and Elements Editorial Committee (CEEC).