The secondary reflector, if any, is often called the subreflector . While smaller than the primary reflector, it is often large relative to a person. A powerful macro-based text formatter written by Donald Knuth, popular in the scientific community. The language was effectively frozen in 1985. TeX can be obtained from the labrea.stanford.edu archive at Stanford University.
Application programs can use the tags to accept or ignore fields, depending on their capabilities.
A term used to describe a VLBI observing mode at the WSRT wherein all antennas are autocorrelated to obtain a large collecting area without high spatial resolution. See phased array . Many different time systems are relevant in astronomy. See atomic time , local sidereal time , sidereal day , Universal Time , UTC . When, for example, the visibility data along a u-v track are averaged, with equal weight, over time intervals of width t sec.