Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://www.stsci.edu/instrument-news/handbooks/ghrs/GHRS_40.html
Дата изменения: Wed Feb 14 17:44:54 1996 Дата индексирования: Sat Dec 22 16:58:50 2007 Кодировка: Поисковые слова: п п п п п п п п п п п п п п п п п п п п п п п п п п п п |
Whenever possible, we recommend that faint objects be acquired by offsetting from a nearby and brighter point source. If accurate coordinates are used, this method should be reliable. However, such objects are not always present next to targets of astrophysical interest. Also, obtaining a good astrometric position of an extended source can be prevented by its large saturated area on the photographic plates upon which the Guide Star Catalog is based. In these cases a direct target acquisition will need to be attempted, and it should succeed if the object provides enough ultraviolet photons. The procedure closely follows that for point sources just described: