Azimuth is the compass direction to face, measured clockwise from north; elevation is how high to look, from 0° at the horizon to 90° overhead.
To point at anything in the sky you need two numbers. Azimuth says which way to face: it is measured clockwise from true north around the horizon, so north is 0°, east 90°, south 180° and west 270°. Elevation says how high to look: the angle up from the horizon to the object, so 0° is the horizon and 90° is straight overhead.
These are the numbers this site computes for every satellite and pass. It uses satellite.js to turn the satellite's estimated position and your location into a ‘look angle’: azimuth, elevation and the straight-line distance (range).
You do not need instruments. A fist held at arm's length covers roughly 10° of sky. So a pass with a Max height of 40° means about four fists up from the horizon. A listed height of 90° means the satellite passes directly overhead.
The site rounds azimuth to one of 16 compass points — N, NNE, NE, ENE, E and so on — for the Look line on each pass card, for example SW → NE. On the Where to look compass it shows the exact figure too, such as SW · 226°.
Mathematically a satellite is ‘up’ the moment its elevation goes above 0°. In a real Indian city, buildings, trees and haze hide the lowest part of the sky. So this site counts a satellite as visible only once it is at least 10° above the horizon. A pass whose highest point is 12° is real but hard to see; one that reaches 60° or more is easy, because it is high, close and bright.
Worked example: from Delhi, an ISS pass might be listed as Look W → SE, Max height 65°. Face west at the start time, look a little above the rooftops, and follow it as it climbs to about six and a half fists up before sinking to the south-east.
Each pass card's Look line gives the azimuth as compass points (start → end) and Max height gives the peak elevation in degrees. See tonight's passes over Delhi
Look angles come from a coordinate change. SGP4 gives the satellite's position r_sat in an Earth-centred inertial frame. This site rotates it to Earth-fixed coordinates using Greenwich sidereal time, then subtracts the observer's Earth-fixed position r_obs to get the range vector ρ = r_sat − r_obs. Projecting ρ onto the observer's local south, east and up directions (the SEZ frame) gives components (ρS, ρE, ρZ), and:
satellite.js does this in ecfToLookAngles(); the site converts radians to degrees and wraps azimuth with (az + 360) mod 360.
Worked example: how far away is the ISS when it is low? With Earth radius R = 6,378 km, orbit height h = 420 km and elevation E = 10°, the slant range is ρ = √((R + h)² − (R cos E)²) − R sin E = √(6,798² − 6,281²) − 1,108 ≈ 2,600 − 1,108 ≈ 1,490 km. Overhead (E = 90°) it is just 420 km. That 3.5-fold difference in distance is why low passes look much fainter.
The 16-point compass uses sectors of 360/16 = 22.5°; the site picks the point with round(az / 22.5) mod 16. NOAA notes that refraction lifts objects near the horizon slightly; this site does not model it, another reason to ignore the lowest few degrees.
SW is about 225° and NE about 45°, so the satellite rises in the south-west and sets in the north-east.
About three fists at arm's length, since one fist covers roughly 10°.
It is much farther away — for the ISS about 1,490 km instead of 420 km — and its light also passes through more atmosphere.