Arcsecond (″) - Unit Information & Conversion
🔄 Quick Convert Arcsecond
What is a Arcsecond?
Arcsecond (arcsec or second of arc) is 1/3600 of a degree, measuring tiny angles in astronomy and precision optics. Symbol: ″. 1° = 3600 arcseconds. Used for stellar parallax, telescope resolution, and GPS precision.
History of the Arcsecond
Derived from Babylonian sexagesimal system. Critical for astronomical measurements since telescope invention (1600s). Modern usage includes satellite positioning and high-precision surveying.
Quick Answer
What is an Arcsecond? An arcsecond is 1/3600 of a degree, used for measuring extremely small angles. A penny viewed from 4 km away appears about 1 arcsecond wide. 1 arcsecond = 1/60 arcminute = 1/3600 degree ≈ 0.000278°. Use our angle converter for instant conversions.
Definition
1 arcsecond = 1/60 arcminute = 1/3600 degree ≈ 0.000278° ≈ 0.00000485 radians
Symbol: ″ (double prime) or arcsec
Key conversions:
- 60 arcseconds = 1 arcminute
- 3600 arcseconds = 1 degree
- 1 arcsecond ≈ 4.848 × 10⁻⁶ radians
Common Uses
Astronomy: Measuring star positions, planetary motion, stellar parallax, and telescope resolution. Surveying: High-precision land measurements and geodetic surveys. GPS Systems: Coordinate precision (1 arcsecond ≈ 30 meters at equator). Optics: Telescope and microscope angular resolution specifications.
Real-World Examples
Astronomical Measurements
- Stellar parallax: Nearest star (Proxima Centauri) has 0.768 arcsecond parallax
- Hubble Space Telescope resolution: ~0.05 arcseconds
- Jupiter's moons: Callisto orbits ~140 arcseconds from Jupiter
- Mars polar ice cap: ~15 arcseconds diameter when viewed from Earth
- Saturn's rings: Main ring system spans ~40 arcseconds
Distance Scale on Earth
- 1 arcsecond at equator: ≈ 30.9 meters (101 feet)
- 1 arcsecond latitude: Always ≈ 30.9 meters
- 1 arcsecond longitude: Varies by latitude:
- Equator: 30.9 m
- 45° latitude: 21.9 m
- 60° latitude: 15.5 m
Visual Comparisons
- Human hair: ~20 arcseconds at 1 meter distance
- Tennis ball: ~3600 arcseconds (1°) at 10 meters
- Penny (19mm): ~1 arcsecond at 4 km distance
- International Space Station: ~60 arcseconds when overhead
Arcsecond Conversion Formulas
To Degree:
To Radian:
To Gradian:
To Arcminute:
To Turn:
To Revolution:
To Quadrant:
To Gon:
To Mil:
Frequently Asked Questions
Formula: Degrees = Arcseconds ÷ 3600 Examples:
- 3600 arcseconds = 1°
- 1800 arcseconds = 0.5°
- 60 arcseconds = 1 arcminute = 0.0167°
- 1 arcsecond ≈ 0.000278° Arcseconds to Degrees converter →
Convert Arcsecond
Need to convert Arcsecond to other angle units? Use our conversion tool.