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API · /starmagnitude-api

Star Magnitude & Distance API

healthy 3,856 Subscribers

Stellar magnitude and distance maths as an API, computed locally and deterministically. The magnitude endpoint works the distance modulus, m − M = 5·log₁₀(d/pc) − 5 — give any two of the apparent magnitude m, the absolute magnitude M and the distance and it returns the third, with the distance in parsecs, light-years and astronomical units (the absolute magnitude is the apparent magnitude a star would have at 10 parsecs). The flux endpoint applies Pogson's relation to turn a magnitude difference into a brightness ratio, F₁/F₂ = 10^(0.4·(m₂ − m₁)), where five magnitudes is exactly a hundredfold change in brightness — from two magnitudes, a magnitude difference or a ratio. The parallax endpoint converts a parallax angle into a distance, d(pc) = 1 ÷ p(arcseconds), and back, the geometric method behind the parsec itself. Everything is computed locally and deterministically, so it is instant and private. Ideal for astronomy-education, planetarium, stargazing and science app developers, observing and astrophysics tools, and STEM teaching. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is stellar magnitude and distance; for orbital mechanics use an orbital API and for great-circle distances on Earth a geo-distance API.

#astronomy #magnitude #parallax #parsec #astrophysics #developer-tools
api.oanor.com/starmagnitude-api
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Machine-readable spec so AI agents can integrate this API.

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

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

Star Magnitude & Distance API — live data on the oanor API marketplace

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
75 ms
Server probes · 24h
Subscribers
3,856
active
Total calls
80
last 7 days
status Full status page → · 16 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 3,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • Apparent ↔ absolute magnitude via distance modulus m−M=5·log₁₀(d/pc)
  • Parallax → distance in parsecs and light-years
  • JSON responses, no API-data charges
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Starter

€5.00 /month

  • 40,000 calls / month
  • 5 requests / second
  • Hard cap (429 above quota, no overage)
  • All magnitude & distance endpoints
  • Parsec / light-year / AU unit conversions
  • Deterministic results for classroom and lab use
  • Email support
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Pro

€15.00 /month

  • 250,500 calls / month
  • 15 requests / second
  • Hard cap (429 above quota, no overage)
  • Higher throughput for catalog batch jobs
  • Distance modulus + parallax + extinction-aware magnitude
  • Bulk-friendly low-latency local compute
  • Priority support
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Mega

€49.00 /month

  • 1,608,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • Maximum quota for survey-scale pipelines
  • Full stellar magnitude & distance toolkit
  • Highest rate limit for parallel workloads
  • Priority support + SLA
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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.

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Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Star Magnitude & Distance API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Star Magnitude & Distance API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Star Magnitude & Distance 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 Star Magnitude & Distance API cost?
Star Magnitude & Distance 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 Star Magnitude & Distance API GDPR-compliant?
All requests to Star Magnitude & Distance 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/starmagnitude-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/starmagnitude-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/starmagnitude-api/SOME_PATH");
curl_setopt($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/starmagnitude-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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