# Name of this angle?

Given a planet and a point $P$, is there an existing name for the angle $\theta$ as seen in the diagram below? If not, what would you call it? ("Angle of elevation"?)

Thanks!

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Question not clear. Where's the planet in the diagram? Where's the point? Where's the observer? What does $r$ mean? – Gerry Myerson Jun 14 '12 at 5:41
@Gerry: Sorry! The circle represents the planet. $P$ is the point (which is the location of the observer). $r$ is the radius, and doesn't really add to the question at all. – Cameron Jun 14 '12 at 5:42
I think you're asking about the "angular radius" of the planet, although a more commonly used concept is the "angular diameter". – Gerry Myerson Jun 14 '12 at 5:42

@GerryMyerson: Sorry if I wasn't clear. The angular diameter would be $2\arcsin(r/D)$, where $D$ is the distance from the observer to the centre of the sphere. The OP's angle is $\arctan(r/D)$, so it is a (very) little smaller than $\arcsin(r/D)$. – André Nicolas Jun 14 '12 at 7:17