Origin of Star Finders
Star Finder or Planisphere was first used in ancient Rome. It was the iconic architect and engineer Vitruvius who in 27 B.C described a star map that was etched on a solid plate and also consisted of a horizon mask. This horizon mask circulated over to show the risings of various celestial bodies
By the 4th century A.D scientists started using planispheric astrolabe. It was then used by Medieval Arabs and Persians. By the end of the Middle Ages, astronomers started using astrolabes to witness the Sun and stars.
Later, the invention of clocks resulted in a more sophisticated instrument to locate stars and constellations. This is how planisphere came into being.
How does a star finder work?
A star finder works in a simple way. It consists of a circular base which shows the days and months of the year around the edge of a circular base. It also displays the hours of the day around the overlay.
As soon as you turn the overlay in order to line up the time of your observations along with the date, the apparent portion of the sky will be displayed through the small opening in the overlay. You just need to hold the star finder over your head and continue orienting it with respect to North.
Issues with Planisphere or Star Finder
‘Planisphere’ literally means flat sphere. Although, avid star lovers use planisphere to locate stars and constellations, design issues continue to persist. Often the map on star finder is extremely small and distorted. This results in compressing the celestial hemisphere above and around. You should remember that star patterns will look bigger in real life than on the map.
Since the map is usually small, it becomes difficult to move your eyes to witness the constellation. As a result, it seems like the star finder is showing the east and west horizons together while in reality it the east is in front of you and the west is behind your back.
However, you can still manage to use it correctly by holding the planisphere in front of your eyes as you see the horizon. As you twist it around, the part of the map which is labelled with the direction comes at the bottom. Consequently, the correct horizon will appear horizontally on the map in order to match the horizon in front of you. Now you can compare stars above the horizon on the map with those you're able to see on the sky.
No matter you love to gaze at the stars or not, locating them on sky by using a star finder is, indeed, a beautiful experience!