With professional telescopes, or even reasonably good amateur telescopes,

it's possible to point and shoot to target a telescope and

go very precisely to a region of sky within less than a degree.

But to do observational astronomy, or learn the night sky,

you can estimate angles very simply without using a telescope.

In simple terms, if you want to know angular measurement,

where 90 degrees is the angle between the zenith, the point overhead, and

any horizon, your full handspan held out at arm's length is about 20 degrees.

Your fist width is about 10 degrees, and

an index finger width is about a degree, held at arm's length.

That's twice the diameter of the full moon,

which subtends half a degree, as does the sun.

There's a basis for getting angular measurement and

indeed, amateur astronomers and anyone without a telescope,

you can step your way around the sky just using those single units of measurement.

In positional astronomy, where the celestial sphere is the frame of

reference, we can define the position of any star or

any object in the night sky with two angles.

Just as we can define a position on the Earth's surface by latitude and longitude.

Astronomers use two different frames of reference for measuring angles.

The simplest is altitude and azimuth.

Altitude is the elevation directly going straight up

from any horizon to the object of interest.

And azimuth is the angle around the horizon from

some fixed point like due north or due south.