preceding limb

preceding limb

[prē′sēd·iŋ ′lim]
(astronomy)
The half of the limb of a celestial body with an observable disk that appears to precede the body in its apparent motion across the field of view of a fixed telescope.
References in periodicals archive ?
It takes 50 minutes for a feature to rotate from Jupiter's central meridian halfway to the preceding limb.
Evening clouds have the same appearance as morning clouds but occur on the planet's preceding limb.
Start this drawing as close to the preceding limb as you can, and continue from there toward the planet's central meridian (CM).
The winds along the northern edge of the SEB, known as the South Equatorial jet stream, blow at more than 200 miles (320 kilometers) per hour in the direction of Jupiter's preceding limb, while the prevailing winds along the southern edge of the SEB, known as the SEBs jet stream, blow toward the planet's following limb at speeds that can exceed 300 miles (480 km) per hour.
Observers with access to a stopwatch and an accurate time source can make timings of the various stages: the preceding ansae (tips) of rings A and B, preceding limb of disk, center of disk, following limb of disk, and following ring ansae.