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How to Look Up Orion’s Coordinates Using JPL Horizons

A step-by-step guide for Artemis II observers

There’s no login required — JPL Horizons is a free, public system with no account needed. Here are the instructions:

  1. Go to the Horizons web app. Open ssd.jpl.nasa.gov/horizons/app.html in your browser.
  2. Set the Target Body. Click the “Edit” button next to Target Body. In the search box type Artemis II or enter the object number -1024. Select “Artemis II (spacecraft) (Integrity)” from the results.
  3. Set your Observer Location. Click “Edit” next to Observer Location. You can type a city name (e.g., “London, UK”), enter geographic coordinates (longitude, latitude, altitude), or use an observatory code (e.g., 675 for Palomar). This gives you topocentric coordinates specific to your location, including altitude and azimuth so you know exactly where to point.
  4. Set the Time Span. Click “Edit” next to Time Specification. Enter your start and stop times in UTC (e.g., Start: 2026-04-02 20:00, Stop: 2026-04-03 06:00). Set the Step Size — use small intervals like 5 min or 10 min for close passes when the spacecraft moves quickly, or 1 h to 4 h for the cruise phases.
  5. Choose what data you want. Click “Edit” next to Table Settings. The most useful quantities are:
    1, 2
    Right Ascension and Declination (where to point your telescope)
    4
    Azimuth and Elevation (compass direction and height above your horizon)
    9
    Visual magnitude (will show “n.a.” for this spacecraft, so use Molczan’s estimates below)
    20
    Range in AU (multiply by 149,598 to get km)
    23
    Solar elongation (how far from the Sun in the sky; higher is better for observing)
  6. Generate the ephemeris. Click “Generate Ephemeris.” The results table shows the spacecraft’s sky position at each time step. Negative elevation values mean the spacecraft is below your horizon.

Quick Tips

Molczan Magnitude Estimates for Artemis II

Since Horizons does not provide magnitude estimates for the Artemis II spacecraft, satellite observer Ted Molczan has produced rough estimates based on published NASA dimensions. To estimate how bright the spacecraft will appear, find the range (delta) from your Horizons output and look up the corresponding magnitude in the table below.

Standard magnitudes (at 1,000 km range, 90° phase angle):

Orion spacecraft (crew + service module): 4.6
ICPS + spacecraft adapter: 3.9 (subtract 0.7 from table values)

Estimated uncertainty: ±2 magnitudes

Range (AU)Range (km)Mag (100% Ill.)Mag (50% Ill.)
0.000011,4964.25.5
0.000022,9925.77.0
0.000034,4886.67.9
0.000045,9847.28.5
0.000057,4807.79.0
0.000068,9768.19.4
0.0000710,4728.59.7
0.0000811,9688.710.0
0.0000913,4649.010.2
0.0001014,9609.210.5
0.0002029,92010.712.0
0.0003044,87911.612.9
0.0004059,83912.213.5
0.0005074,79912.714.0
0.0006089,75913.114.4
0.00070104,71913.514.7
0.00080119,67813.715.0
0.00090134,63814.015.2
0.00100149,59814.215.5
0.00110164,55814.415.7
0.00120179,51714.615.9
0.00130194,47714.816.0
0.00140209,43715.016.2
0.00150224,39715.116.3
0.00160239,35715.216.5
0.00170254,31615.416.6
0.00180269,27615.516.7
0.00190284,23615.616.9
0.00200299,19615.717.0
0.00210314,15615.817.1
0.00220329,11515.917.2
0.00230344,07516.017.3
0.00240359,03516.117.4
0.00250373,99516.217.5
0.00260388,95416.317.5
0.00270403,91416.417.6

These values are for the Orion capsule. For the ICPS upper stage (if tracked separately), subtract 0.7 magnitudes (i.e., it is brighter).

Equipment Reference

EquipmentApprox. Limiting Magnitude
Naked eye (dark sky)6.0 – 6.5
7×50 binoculars9 – 10
6-inch (150 mm) telescope~13
8-inch (200 mm) telescope~14
12-inch (300 mm) telescope~15
16-inch (400 mm) telescope~16

Magnitude estimates credit: Ted Molczan, via SeeSat-L mailing list