Astro*Dictionary
by Michael Erlewine

2 articles for
"Refraction"

The bending of light rays as they pass from one transparent medium to another transparent medium of a different density, e.g., from air to water, or interstellar space to air. This is important when viewing planet's rising or setting and can amount to a positional correction of about 34.5' at an altitude of 0°; i.e., on the Horizon.

 

See also: ♦ Rise/set/transit

The apparent "bending" of the light rays from a body asits ligh passes through the Earth's atmosphere. The bending is greatest near the Horizon, and is of such a nature that the body can be "seen" after it has astronomically "set". The nominal refraction at an altitude of zero degrees is about 34.5 minutes of arc.

 

See also: ♦ Rise/set/transit