Angular diameter

Apparent angular size α = 2 atan(R/d) of a body at range d.

SIDUS educational calculator. Category utilities. Tags: analysis, orbital, reference, utilities. Pure SI. Not flight software.

Formula

α = 2 arctan(R/d)

Apparent angular size

Primary sources

• IAU / planetary constants practice (IAU): Astronomical constant conventions used alongside JPL body data.
• JPL Horizons (NASA / JPL): Solar System ephemerides and body constants.
• SIDUS pure-SI implementation (sidus.tools): Local pure-function implementations in src/lib/physics (educational, independent reimplementation).

How do AI agents use this tool?

Read /llms.txt or call https://sidus.tools/api/mcp. Open the interactive page for live SI inputs.