A direction described by one or more angles relative to a specified reference.

Interferometric angular diameter ( $V (B) = 2 J_{1} (π B Θ/ λ) / (π B Θ/ λ)$ )

An angular diameter inferred from the interferometric visibility of an extended source. The displayed monochromatic formula is for a uniformly bright circular disk, with projected baseline

B

, diameter

Θ

and wavelength

λ

. Its first visibility zero gives

B Θ/ λ ≃ 1.22

. Stellar angular diameter from a visibility envelope describes this calibration; real photospheres require limb-darkening corrections.

Minute and second of arc

 0  0

A minute of arc is one sixtieth of a degree; a second of arc is one sixtieth of a minute of arc. These units describe small astronomical angles, including astronomical seeing.

Arcsecond ( $1^{''} = π /648000 rad$ )

 0  0

An arcsecond is

1/3600

of a degree, equivalently

π /648000

radians. There are approximately

206265

arcseconds in a radian.

Milliarcsecond ( $mas$ )

 0  0

One thousandth of an arcsecond:

1 mas = π / (648000000) rad

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Angle by

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An angle is a geometric figure formed by two rays (or line segments) that have a common endpoint, known as the vertex. The measure of an angle is typically expressed in degrees or radians and represents the amount of rotation required to align one ray with the other. Angles can be classified into several types based on their measure: 1. **Acute Angle**: Less than 90 degrees. 2. **Right Angle**: Exactly 90 degrees.

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Angle by