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API · /lighttime-api

Light Travel Time API

healthy 4,804 Subscribers

Light-travel-time astronomy maths as an API, computed locally and deterministically. The travel-time endpoint computes how long light takes to cross a distance, t = d/c with c = 299,792,458 m/s exactly, accepting the distance in metres, kilometres, miles, astronomical units, light-years, parsecs or light-seconds/minutes and returning the time in seconds, minutes, hours, days and years — light from the Sun reaches Earth in about 8.3 minutes and the nearest star is about 4.2 light-years away. The distance endpoint inverts the relation, d = c·t, to give how far light travels in a time, returning the distance in metres, kilometres, astronomical units, light-years and parsecs — one light-year is about 9.461×10¹⁵ m. The round-trip endpoint computes the one-way and round-trip communication delay to a target, d/c and 2·d/c, the light-speed latency that makes distant spacecraft control so slow and Mars rovers largely autonomous. Distance units include light-second and light-minute and time units run from seconds to years. Everything is computed locally and deterministically, so it is instant and private. Ideal for astronomy, space-mission, education, science-communication and simulation app developers, communication-delay and cosmic-distance tools, and physics teaching. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is light travel time; for an object's angular size use an angular-size API and for sidereal time a sidereal API.

#light-time #astronomy #light-year #speed-of-light #communication-delay #developer-tools
api.oanor.com/lighttime-api
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Machine-readable spec so AI agents can integrate this API.

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

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

Light Travel Time API — live data on the oanor API marketplace

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
81 ms
Server probes · 24h
Subscribers
4,804
active
Total calls
76
last 7 days
status Full status page → · 12 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 4,800 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 4,800 calls/month
  • 2 req/sec
  • Travel time + distance + round-trip
  • No credit card
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Starter

€4.00 /month

  • 47,500 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • 47,500 calls/month
  • 6 req/sec
  • AU/ly/pc units, comms latency
  • Email support
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Pro

€11.00 /month

  • 222,000 calls / month
  • 15 requests / second
  • Hard cap (429 above quota, no overage)
  • 222,000 calls/month
  • 15 req/sec
  • Space-mission & education pipelines
  • Priority support
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Mega

€37.00 /month

  • 1,310,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • 1,310,000 calls/month
  • 40 req/sec
  • Platform scale
  • Dedicated SLA
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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.

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Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Light Travel Time API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Light Travel Time API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Light Travel Time 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 Light Travel Time API cost?
Light Travel Time API has a free tier with 100 calls / month. Paid plans start at €4.00 / 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 Light Travel Time API GDPR-compliant?
All requests to Light Travel Time 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/lighttime-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/lighttime-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/lighttime-api/SOME_PATH");
curl_setopt($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/lighttime-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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