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API · /observatories-api

Observatory Codes API

healthy 4,529 Subscribers

The IAU Minor Planet Center list of observatory codes as an API — every site the MPC uses to identify a telescope when it publishes astrometric observations of asteroids and comets. For each of 2,700+ codes: the 3-character code, the observatory name, its east longitude and the parallax constants (rho·cos φ', rho·sin φ'). From those constants the API derives each site's geocentric latitude and a -180..180 longitude, so you can find the observatories nearest any point on Earth with a great-circle (haversine) search. Look one up by code, search by name, list them all, or find the closest sites to a latitude/longitude. Distinct from telescope-api (optics maths) — this is the registry of real observing sites and where they are. Served from memory — always fast.

#astronomy #observatories #mpc #telescopes #geospatial #science
api.oanor.com/observatories-api
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Machine-readable spec so AI agents can integrate this API.

/api/observatories-api/openapi.json
/api/observatories-api/llms.txt

Discovery: GET /api/index.json lists every API.

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
96 ms
Server probes · 24h
Subscribers
4,529
active
Total calls
35
last 7 days
status Full status page → · 10 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 12,000 calls / month
  • 3 requests / second
  • Hard cap (429 above quota, no overage)
  • 12k calls/month
  • 3 req/sec
  • All endpoints
  • No credit card
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Starter

€5.00 /month

  • 120,000 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 120k calls/month
  • 8 req/sec
  • Email support
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Pro

€15.00 /month

  • 600,000 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 600k calls/month
  • 20 req/sec
  • Priority support
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Mega

€36.00 /month

  • 3,000,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 3M calls/month
  • 50 req/sec
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

Meteorites API

NASA's catalogue of 45,000+ meteorites recovered on Earth as an API. For each meteorite: its name, NASA id, classification (recclass, e.g. L5, Iron), mass in grams, whether it was seen to fall or simply found, the year, and the latitude/longitude where it was recovered. Look one up by name or id, find the meteorites NEAR any coordinate (great-circle distance), rank by mass or year, list a classification or year, or search. Great for space, education, mapping and museum apps. Distinct from asteroids and close-approach data — these are rocks already on the ground.

api.oanor.com/meteorites-api

Constellations API

The 88 modern IAU constellations as an API — the reference an astronomy app, planetarium or education tool needs. For each constellation: its official IAU abbreviation, English name, the Latin genitive used when naming stars (e.g. "Alpha Andromedae"), a size rank, the approximate centre in equatorial coordinates (right ascension / declination) and the constellation name in roughly 25 languages. Look one up by abbreviation or name, search across every language, find which constellation a sky position falls nearest to, or list them all. Distinct from stars-api (individual stars) — this is the reference for the constellations themselves. Served from memory — always fast.

api.oanor.com/constellations-api

Sundial API

Sundial gnomonics maths as an API, computed locally and deterministically — the hour-line, gnomon and longitude-correction numbers a dial maker, horologist or astronomy hobbyist lays a sundial out with. The hour-line-angle endpoint gives the angle of each hour line on the dial plate, measured from the noon line: for a horizontal dial tan(angle) = sin(latitude) × tan(hour angle), and for a vertical south-facing dial cos(latitude) is used instead, where the hour angle is 15° per hour from solar noon. At 50° latitude the 1-o'clock line sits about 11.6° from noon rather than 15° — the lines bunch near noon and spread toward the ends, which is exactly why a sundial's hours are unevenly spaced. The gnomon endpoint gives the style angle: the gnomon's shadow-casting edge must point at the celestial pole, so it rises at the latitude angle on a horizontal dial (50° at 50° N) and at 90° − latitude on a vertical dial — get this wrong and the dial keeps correct time at only one season. The longitude-correction endpoint converts the dial's local apparent time to clock time: 4 minutes of time per degree of longitude, correction = 4 × (reference meridian − local longitude), so a dial at 7.5° E on Central European Time reads 30 minutes slow versus the clock. Everything is computed locally and deterministically, so it is instant and private. Ideal for sundial-design and gnomonics tools, astronomy-education and maker apps, and horology calculators. Pure local computation — no key, no third-party service, instant. Add the equation of time for full clock accuracy. 3 compute endpoints. For the sun's position use a solar-position API; for sunrise and sunset a sunrise API.

api.oanor.com/sundial-api

Telescope Optics API

Telescope optics maths as an API, computed locally and deterministically — the magnification, exit-pupil and resolving-power numbers an amateur astronomer or stargazing-app developer picks gear and eyepieces with. The magnification endpoint gives magnification = the telescope's focal length ÷ the eyepiece focal length (a 1000 mm scope with a 10 mm eyepiece is 100×), the focal ratio, and — from the aperture — the useful range from about the aperture in mm ÷ 7 (lowest useful, a 7 mm exit pupil) up to roughly 2× the aperture in mm, beyond which the image only dims and blurs; pass an eyepiece apparent field and it returns the true field of view. The exit-pupil endpoint gives aperture ÷ magnification, the width of the light beam leaving the eyepiece — a big 4–7 mm exit pupil for bright wide views of nebulae, a small 0.5–2 mm for the Moon and planets at high power. The resolution endpoint gives the Dawes limit ≈ 116 ÷ aperture(mm) and the slightly stricter Rayleigh limit ≈ 138 ÷ aperture in arcseconds, plus the limiting magnitude ≈ 2.7 + 5·log₁₀(aperture mm) — bigger glass splits finer doubles and reaches fainter stars, though seeing usually caps real resolution near 1 arcsecond. Everything is computed locally and deterministically, so it is instant and private. Ideal for astronomy and stargazing apps, telescope-shop and eyepiece-calculator tools, and observing-planner utilities. Pure local computation — no key, no third-party service, instant. 3 compute endpoints. For camera/thin-lens imaging use a lens API; for stellar magnitudes a star-magnitude API.

api.oanor.com/telescope-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Observatory Codes API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Observatory Codes API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Observatory Codes API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Observatory Codes API cost?
Observatory Codes API has a free tier with 100 calls / month. Paid plans start at €5.00 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Observatory Codes API GDPR-compliant?
All requests to Observatory Codes API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/observatories-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/observatories-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/observatories-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/observatories-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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