Convert Arcseconds to Milliradians

Convert Arcseconds (″) to Milliradians (mrad) instantly and accurately.

Conversion Formula

mrad = ″ × 0.004848136811

About Arcseconds

An arcsecond (″) is 1/3,600 of a degree - π/648,000 rad ≈ 4.848 × 10⁻⁶ rad. It is the fundamental resolution unit of classical astronomy and geodetic surveying. The Hubble Space Telescope delivers ~0.05″ resolution; atmospheric seeing at excellent sites gives 0.4-0.6″. Stellar parallax of Proxima Centauri is 0.7687″, defining its distance of 1.3009 parsecs. The parsec is defined as the distance at which 1 AU subtends exactly 1 arcsecond - giving 1 pc = 3.0857 × 10¹⁶ m. 1″ = π/648,000 rad ≈ 4.848 µrad.

About Milliradians

A milliradian (mrad) is one thousandth of a radian (10⁻³ rad ≈ 0.05730°). The MIL-dot reticle system in precision rifle scopes uses milliradians for its elegant property: at range R metres, 1 mrad subtends exactly R mm - so at 300 m, 1 mrad = 300 mm; at 1,000 m, 1 mrad = 1,000 mm = 1 m. Semiconductor laser slow-axis divergence is typically 5-15 mrad. Note: 1 mrad ≠ 1 NATO mil (which is π/3,200 rad ≈ 0.9817 mrad). 1 mrad ≈ 0.05730° ≈ 3.438′ ≈ 206.3″.

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