API Documentation

Access astronomical calculations programmatically via our REST API.

Getting Started

The AR00.space Astronomy API provides free access to astronomical calculations. All endpoints return JSON.

Access is provided exclusively through Azure API Management using a free API key — direct calls to the web app are not permitted. The free tier allows 100 requests per day per IP address with a burst limit of 10 requests per minute.

REST Base URL (via APIM)

https://api.ar00.space/ar00

MCP Endpoint (via APIM)

https://api.ar00.space/ar00-mcp

Model Context Protocol server (Streamable HTTP) — 13 astronomy tools for AI agents.

Free API Key

eac6ba7ba5f24c528d69cee8ccb990f7

Pass via header: Ocp-Apim-Subscription-Key: eac6ba7ba5f24c528d69cee8ccb990f7

100

calls / day / IP

calls / min burst

endpoints

Interactive Swagger UI OpenAPI Spec (JSON)

MCP Server for AI agents

Beyond the REST API, AR00.space exposes a Model Context Protocol (MCP) server over Streamable HTTP. AI assistants — Claude, GitHub Copilot, VS Code, and any MCP-compatible client — can call astronomical calculations directly as tools, secured by the same free API key through Azure API Management.

MCP Endpoint

https://api.ar00.space/ar00-mcp

Transport: Streamable HTTP · Auth: Ocp-Apim-Subscription-Key header

13 Tools available

get_sunrise_sunset — sunrise, sunset & twilight

get_solar_position — solar coordinates

get_lunar_position — lunar position & distance

get_moon_phase — phase, illumination, next phases

get_planet_position — single planet ephemeris

get_all_planets — all planets at once

check_solar_eclipse — solar eclipse lookup

check_lunar_eclipse — lunar eclipse lookup

get_active_meteor_showers — showers on a date

plan_tonight — full observing session plan

check_messier_visibility — Messier visibility

get_messier_object — Messier object details

get_rise_transit_set — rise, transit & set times

Client configuration

{
  "mcpServers": {
    "astrocalc": {
      "type": "http",
      "url": "https://api.ar00.space/ar00-mcp",
      "headers": {
        "Ocp-Apim-Subscription-Key": "eac6ba7ba5f24c528d69cee8ccb990f7"
      }
    }
  }
}

REST Endpoints

Sun

Method	Endpoint	Description
GET	`/api/solar/sunrise-sunset`	Sunrise, sunset, and twilight times
GET	`/api/solar/position`	Solar coordinates (RA, Dec, ecliptic)

Parameters & Example

sunrise-sunset: year, month, day, lat, lon, elevation

GET /api/solar/sunrise-sunset?year=2026&month=3&day=21&lat=41.9&lon=12.5&elevation=0

Moon

Method	Endpoint	Description
GET	`/api/lunar/position`	Lunar ecliptic position, distance, angular diameter
GET	`/api/lunar/phase`	Phase name, illumination, age, next phases
GET	`/api/lunar/features`	Catalog of 45+ lunar features
GET	`/api/lunar/features/terminator`	Features near the lunar terminator

Parameters & Example

phase: year, month, day

GET /api/lunar/phase?year=2026&month=3&day=13

Planets

Method	Endpoint	Description
GET	`/api/planets/position`	Single planet position, magnitude, elongation
GET	`/api/planets/all`	All planets at once
GET	`/api/planets/jovian-moons`	Galilean satellite positions (Io, Europa, Ganymede, Callisto)
GET	`/api/planets/saturn-rings`	Saturn ring geometry (tilt, axis, visibility)

Parameters & Example

GET /api/planets/all?year=2026&month=3&day=13&hour=22

Deep Sky

Method	Endpoint	Description
GET	`/api/deepsky/messier`	All 110 Messier objects
GET	`/api/deepsky/messier/{number}`	Single Messier object
GET	`/api/deepsky/stars`	50 brightest stars catalog
GET	`/api/deepsky/doubles`	36+ double star catalog
GET	`/api/deepsky/constellations`	All 88 IAU constellations

Optics

Method	Endpoint	Description
GET	`/api/optics/telescope`	Full telescope calculation suite
GET	`/api/optics/extinction`	Atmospheric extinction at given altitude
GET	`/api/optics/bortle`	Naked-eye limit from Bortle scale

Phenomena

Method	Endpoint	Description
GET	`/api/phenomena/upcoming`	All upcoming events for next N months
GET	`/api/phenomena/meteor-showers`	All 16 major meteor showers
GET	`/api/phenomena/meteor-showers/active`	Active showers on a given date
GET	`/api/phenomena/moon-phase`	Detailed lunar phase information
GET	`/api/phenomena/eclipse/solar`	Solar eclipse check for a given month
GET	`/api/phenomena/eclipse/lunar`	Lunar eclipse check for a given month

Comets

Method	Endpoint	Description
POST	`/api/comets/position`	Compute comet position from orbital elements

Planner

Method	Endpoint	Description
GET	`/api/planner/tonight`	Full observing session plan
GET	`/api/planner/visibility`	Messier object visibility check
GET	`/api/planner/rise-transit-set`	Rise, transit, set times
GET	`/api/planner/observing-window`	Dark sky window and moon conditions

Quick Start

cURL

curl -H "Ocp-Apim-Subscription-Key: \
  eac6ba7ba5f24c528d69cee8ccb990f7" \
  "https://api.ar00.space/ar00\
/api/solar/sunrise-sunset\
?year=2026&month=3&day=21\
&lat=41.9&lon=12.5"

JavaScript

                const base = 'https://api.ar00.space/ar00';
const key = 'eac6ba7ba5f2...';

const res = await fetch(
  `${base}/api/lunar/phase` +
  `?year=2026&month=3&day=13`,
  { headers: {
    'Ocp-Apim-Subscription-Key': key
  }});
const phase = await res.json();
console.log(phase.phaseName);

Python

import requests

BASE = 'https://api.ar00.space/ar00'
KEY = 'eac6ba7ba5f2...'

r = requests.get(
  f'{BASE}/api/planets/all',
  params={'year': 2026, 'month': 3,
          'day': 13, 'hour': 22},
  headers={
    'Ocp-Apim-Subscription-Key': KEY
  })
planets = r.json()

C# / .NET

var client = new HttpClient();
client.DefaultRequestHeaders.Add(
  "Ocp-Apim-Subscription-Key",
  "eac6ba7ba5f2...");

var json = await client
  .GetStringAsync(
    "https://api.ar00.space/ar00"
    + "/api/deepsky/messier/42");

Azure APIM

The API is served through Azure API Management providing:

100 calls/day per IP — free tier
10 calls/min — burst limit
Header X-RateLimit-Remaining shows calls left
HTTP 429 when limit exceeded

Pass the API key via the Ocp-Apim-Subscription-Key header with every request.

MCP Server

AI agents (Claude, GitHub Copilot, VS Code…) can call AstroCalc directly through the Model Context Protocol endpoint, secured by the same free API key.

{
  "mcpServers": {
    "astrocalc": {
      "type": "http",
      "url": "https://api.ar00.space/ar00-mcp",
      "headers": {
        "Ocp-Apim-Subscription-Key":
          "eac6ba7ba5f2..."
      }
    }
  }
}

Exposes 13 tools: sunrise/sunset, solar & lunar position, moon phase, planet positions, eclipses, meteor showers, tonight’s plan, Messier visibility and more.

Notes

All times are in Universal Time (UT)
Coordinates use decimal degrees
Positive longitude = East
Positive latitude = North
Dates use Gregorian calendar
All endpoints return JSON
Errors return { "error": "..." }