An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A device that is commonly used to measure the → seeing at optical astronomical sites. The DIMM delivers an estimate of the → Fried parameter based on measuring the variance of the differential image motion in two small apertures, usually cut out in a single larger telescope pupil by a mask. The DIMM concept was introduced by Stock & Keller (1960, in Stars and Stellar Systems, Vol. 1, ed. G. P. Kuiper & B. M. Middlehurst, p. 138), whereas its modern implementation was first described by Sarazin & Roddier (1990, A&A 227, 294).

→ differential; → image; → motion; → monitor.

1) (v.) To watch closely or evaluate something on a constant or regular basis.
To oversee, supervise, or regulate.
2) (n.) A video device that displays data or images generated by a computer or terminal.

From L. monitor "one who reminds, admonishes, or checks," from monere "to remind, warn, advise," related to memini "I remember, I am mindful of," mens "mind," from PIE base *men- "to think;" Pers. cognates under → idea.

Pahregar "watch, guard," agent noun from pahré (Dehxodâ) "watch, guarding," from Mid.Pers. pahr, pahrag "guard;" Av. pāθra.vant "guard, watchman," from *pāθra-, from Av. pā- "to protect," pāti "guards," nipā(y)- (with → ni-) "to watch, observe, guard," nipātar- "protector, watcher," nipāθri- "protectress;" cf. Skt. pā- "to protect, keep," tanû.pā- "protecting the body," paś.pā- "shepherd;" Gk. poma "lid, cover," poimen "shepherd;" L. pascere "to put out to graze," pastor "shepherd;" Lith. piemuo "shepherd;" PIE base *pā- "to protect, feed."
Pahridan verb from pahr, as above.

An optical instrument that follows the variation of → atmospheric turbulence by continuously measuring the → seeing conditions.

→ seeing; → monitor.