The method of starting from an easy bright star and hopping from star to star, chart in hand, to the target. A finder or Telrad and the known size of its field help. It is slow at first, but it is how you learn the sky.
ToolsInteractive atlas, Eyepieces
Related terms
- Telrad
A finder with no magnification that projects three red circles of 0.5°, 2° and 4° onto the sky. The circles act as a scale for hopping from a bright star. Many star atlases print these circles to make finding objects easier.
- Finder scope
The small scope fixed on the tube, with low power and a wide field (for example 8×50, about 6°), that helps you aim. Align it with the main telescope in daylight on a distant object. In a straight-through finder the image is upside down.
- True field
The patch of sky actually visible in the eyepiece. As a first approximation it is the apparent field divided by the magnification: a 52° eyepiece at 50× shows about 1°, twice the width of the full Moon. The exact figure comes from the field stop.
- Asterism
An easily recognised star pattern that is not an official constellation. The Plough (Big Dipper) in Ursa Major, the Summer Triangle (Vega, Deneb, Altair) and the W of Cassiopeia are examples. Asterisms are handy signposts for finding your way.
← The whole glossary