Meridian Altitude Calculator
Find the highest and lowest geometric altitudes and classify horizon crossings at a chosen latitude.
Calculate locally
No account, API or uploaded inputs. All calculations run in this browser.
Worked example
At latitude 45° N and declination +60°, the highest altitude is 75° and the lowest is 15°, so the object is circumpolar. At the same latitude, declination −60° remains below the geometric horizon.
Method and units
Maximum altitude = 90° − |latitude − declination|. Minimum altitude = |latitude + declination| − 90°. A positive minimum stays above the horizon; a negative maximum stays below it. Zero is a grazing or horizon boundary.
What this result means
These are ideal geometric extrema, not rise/set times or a visibility guarantee. A mountain, haze, daylight, refraction or a local horizon can hide a target. At the geographic poles or celestial poles, altitude can be constant; boundary targets can lie on the horizon rather than cross it. Coordinates should refer to the intended observation epoch.