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`d = S "/" alpha`

Enter a value for all fields

The **Astronomical Distance (SAF) **calculator uses the small angle formula (SAF) to compute the distance to an astronomical body based on the size of the object or separation between two objects (S) and the angle subtended (α).

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

- (
**S**) Separation (see diagram). - (
**α**) Angle Subtended.

**Distance (D):** The calculator returns the distance in Astronomical Units (ua). However, this can be automatically converted to compatible units (e.g. light-years) via the pull-down menu.

Use the small angle formula (SAF) to compute the distance given the size and angle subtended.

D = S / α

where:

**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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