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`\alpha = ( s / d )`

Enter a value for all fields

The **Astronomical Angle Subtended (SAF) **calculator uses the small angle formula (SAF) to compute the angle subtended (α) of astronomical observations based on the size of the object or separation between objects (S) and the distance (D)

**INSTRUCTIONS**: Choose units and enter the following:

- (
**S**) This is the size of the object or the distance of separation between two objects (see diagram) - (
**D**) This is the distance to the object

**Angle Subtended(α):** The calculator returns the angle in arc seconds. However, this can be automatically converted to compatible units via the pull-down menu.

Use the small angle formula (SAF) to compute the angle subtended by an astronomical object given the size and distance is:

α = S / D

**D**is the Small Angle Formula Distance to the object.**S**is the size of the object.**α**is the angle subtended.

This is an essential step in computing distance with the parallax method. **Note:** some textbooks show this formula with a coefficient of 2.06 x 10^{5}. This is the equivalent to the formula used here, because vCalc makes the appropriate unit conversions from arc-seconds to radians and does not require the 2.06 x 10^{5} coefficient.

- Hubble's Law
- Kepler's 3
^{rd}Law formula T² = (4π • R³)/(G • M) - Small Angle Formula
*Small Angle Formula**α = S / D* - Flux and Magnitude formulas
- Telescope formulas
- Mass formulas
- Relative Size Formulas
- Wavelength Formulas
- Luminosity and other Formulas

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