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* [[Spacecraft]] – ''a category that includes all spacecraft except space telescopes''
* [[Telescope]] – ''a category that includes both ground-based and space telescopes; organizations that operate telescopes (for example, the [[National Optical Astronomy Observatory|National Optical Astronomy Observatory (NOAO)]]) are listed under "organization"''
== 0–9 ==
* 1RXH – (''catalog'') 1st [[ROSAT]] X-ray HRI, ''a catalog of sources detected by [[ROSAT]] in pointed observations with its [[High Resolution Imager]]''
* 1RXS – (''catalog'') 1[[ROSAT]] X-ray Survey, ''a catalog of sources detected by [[ROSAT]] in an all-sky survey''
* 2dF – (''instrumentation'') Two-degree Field, ''spectrograph on the [[Anglo-Australian Telescope]]''
* [[2dF Galaxy Redshift Survey|2dFGRS]] – (''observing program'') Two-degree-Field Galaxy Redshift Survey
* 2MASP – (''catalog'') Two-Micron All Sky Survey Prototype, ''an early version of the 2MASS catalog''
* [[Two Micron All Sky Survey|2MASS]] – (''observing program''/''catalog'') Two-Micron All Sky Survey, ''an all-sky survey in the [[near-infrared]]; also used to describe the catalog of sources from the survey''
* 2MASSI – (''catalog'') Two-Micron All Sky Survey, Incremental release, ''one of the versions of the 2MASS catalog''
* 2MASSW – (''catalog'') Two-Micron All Sky Survey, Working database, ''one of the versions of the 2MASS catalog''
* [[2dF-SDSS LRG and QSO survey|2SLAQ]] – (''observing program'') 2dF-[[Sloan Digital Sky Survey|SDSS]] [[Luminous red galaxy|LRG]] And [[Quasar|QSO]] survey
* 6dF – (''instrumentation'') Six-degree Field, ''spectrograph on the [[UK Schmidt Telescope|UKST]]''
== A ==
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