Observations of these occulations can give information about the angular diameter of a star, or about close companions.
22.
The cluster has a visual magnitude of 4.5 and spans an angular diameter of 20 arc seconds.
23.
For example, the full moon has an angular diameter of approximately 0.5? when viewed from Earth.
24.
Applying trigonometry ( angular diameter ), this is equivalent to an apparent 4.96?angle in the sky.
25.
Occasionally, the symbols \ chi or r are used to denote both the comoving and the angular diameter distance.
26.
If so, it likely has a small angular diameter; if not, it likely has a large diameter.
27.
Angular diameter distances to the lenses and background sources are important for converting the lensing observables to physically meaningful quantities.
28.
:Someone with 20 / 20 vision can ( by definition ) resolve something 1 arc minute in angular diameter.
29.
The distance can also be derived by comparing changes in the angular diameter with the measured radial velocity in the atmosphere.
30.
These are much larger than the Sun's angular diameter, so total solar eclipses are caused by these moons.
