HOME Space Calculator

Various space calculators for education and learning.

Sky Coordinates: RA/Dec ⇄ Az/Alt

Observer & Time

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Use the same location and time for both conversion directions.

RA/Dec → Az/Alt

Enter values and convert.

Az/Alt → RA/Dec

Enter values and convert.

Distance Unit Converter

Update any box to refresh the others.

Distance ⇄ Time at the Speed of Light

Update either side. Uses c = 299,792.458 km/s.

Frequency ⇄ Wavelength

Update either side. Uses λ = c / f.

Doppler Frequency Shift

Relativistic line-of-sight Doppler calculator for electromagnetic waves.

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Colour (RGB) ⇄ Visible Wavelength

Approximate nearest visible spectral wavelength. Many RGB colours are not pure single-wavelength colours, so this is only an estimate.

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Angular Size

Calculate apparent angular size from real size and distance.

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Orbital Period (Circular Orbit)

Useful for quick orbit estimates around Earth, Moon, Mars or the Sun.

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Escape Velocity

Compute escape velocity from mass and radius.

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Blackbody Peak (Wien's Law)

Update either side: λmax T = 2.897771955 × 106 nm·K.

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The astronomy conversion uses the entered observer coordinates and local date/time.
The RGB-to-wavelength feature returns the nearest single-wavelength visible colour and is approximate.