Content deleted Content added
Fgnievinski (talk | contribs) |
Fgnievinski (talk | contribs) |
||
Line 93:
=== Astronomy ===
In [[astronomy]], the [[angular size]] or angle subtended by the image of a distant object is often only a few [[arcsecond]]s (denoted by the symbol ″), so it is well suited to the small angle approximation.<ref name=Green1985/> The linear size ({{mvar|D}}) is related to the angular size ({{mvar|X}}) and the distance from the observer ({{mvar|d}}) by the simple formula:
:<math>D = X \frac{d}{206\,265{''}}</math>
where {{mvar|X}} is measured in arcseconds.
The
The exact formula is
:<math>D = d \tan \left( X \frac{2\pi}{1\,296\,000{''}} \right)</math>
and the above approximation follows when {{math|tan ''X''}} is replaced by {{mvar|X}}.
| |||