Skyline Astro

Astronomy API for astrology apps

Chart positions you can verify.

Planets, Chiron, nodes, Lilith, Ascendant, MC and houses in one JSON call. Benchmarked against Swiss Ephemeris on 565 reference charts. Hosted in the EU, with nothing from your requests kept.

2,000 free charts a monthNo cardSign in with Google

Loading a benchmark case
Largest difference from Swiss Ephemeris: –
565

reference charts checked against Swiss Ephemeris 2.10

≤23″

largest difference on any point, typical 1–3″

200yrs

from 1900 to 2100, Chiron included

0

birth dates or coordinates stored, cached or logged

01 — What you get

One call. The whole chart.

You send a UTC moment and a place. You get back every position your app draws, in degrees with six decimals.

☉︎☽︎☿︎♀︎♂︎♃︎♄︎♅︎♆︎♇︎

Sun to Pluto

Longitude, latitude and daily speed, with a retrograde flag ready for your interface.

⚷︎

Chiron, from JPL data

Built from NASA JPL Horizons, interpolated and checksummed. Covered across the full 1900–2100 range.

☊︎☋︎⚸︎

Nodes and Lilith

True and mean lunar nodes, both south nodes, and mean Black Moon Lilith with its latitude.

AC · MC

Angles

Ascendant, Midheaven and ARMC, computed for the exact place and moment.

12

Four house systems

Placidus, Porphyry, Whole Sign and Equal. Above the polar circle Placidus switches to Porphyry and the response says so.

10×

Batch requests

Up to ten charts per call. Synastry, composite inputs and transit lists cost one round trip.

A good fit ifyour app writes its own interpretations and needs positions it can stand behind. Signs, aspects and texts stay yours.

02 — Developers

Your first chart in three steps.

Plain HTTPS and JSON, a Bearer key and an OpenAPI 3.1 description. Any language that can make a POST request is ready.

01

Sign in with Google

Your free account opens with 2,000 charts a month.

02

Create a key

Shown once in your console. We keep only its fingerprint.

03

POST /v1/positions

Send UTC moments and places. Read degrees back.

Full reference in the API documentation.

curl https://skylineastro.com/v1/positions \
  -H "Authorization: Bearer $SKYLINE_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "requests": [{
      "datetimeUtc": "1994-07-21T09:42:00Z",
      "latitude": 44.4268,
      "longitude": 26.1025,
      "houses": { "system": "placidus" }
    }]
  }'

03 — Accuracy

Measured, not claimed.

Every release runs against 565 charts computed with Swiss Ephemeris, the reference astrologers check against. Here are the numbers, and the cases behind them.

PointLargestAverage
☉︎Sun2.0″0.5″
☽︎Moon3.2″0.9″
☿︎Mercury9.6″1.9″
♀︎Venus16.0″1.6″
♂︎Mars10.6″1.4″
♃︎Jupiter9.5″2.8″
♄︎Saturn12.0″3.1″
♅︎Uranus11.4″3.0″
♆︎Neptune18.4″9.1″
♇︎Pluto8.4″3.0″
⚷︎Chiron1.3″0.1″
☊︎True node19.4″5.5″
☊︎Mean node0.3″0.1″
⚸︎Lilith (mean)0.7″0.3″
ACAscendant21.1″1.8″
MCMidheaven14.0″1.7″
12Placidus cusps22.7″1.8″
Largest difference: –
PointSkylineSwiss Eph.Δ

One arcsecond (1″) is 1/3600 of a degree. Our release gate is 30″ for every body, angle and cusp, and 5′ for the Ascendant above the polar circle. A 30″ shift moves a planet across a sign boundary only when it sits within half an arcminute of it.

The explorer shows 24 random cases from 1900 to 2025, computed live by the same engine that answers the API. Moments after 2026 depend on a forecast of ΔT (Earth's rotation); there the Moon may differ from other engines by up to about one arcminute toward 2100.

True (osculating) Lilith is held back until it meets the same 30″ gate.

04 — Privacy and licence

Birth data stays with your users.

A birth date and a birthplace identify a person. We built the service so it never needs to remember them.

Nothing from a request is kept

No database row, no cache, no log line with a moment or a coordinate. Logs carry a request id, your account, the status and the latency.

Hosted in the European Union

The API runs on Google Cloud in Belgium (europe-west1). Keys and monthly counters stay in the same region.

An independent engine

Built on open, MIT-licensed astronomy models and NASA JPL data. Not derived from Swiss Ephemeris, so your app takes on no AGPL obligations and no ephemeris licence.

Keys stored as fingerprints

We keep an HMAC fingerprint of each key, never the key. Revoke a key from your console and it stops working within a minute.

05 — Pricing

Start free. Pay as you grow.

One chart is one request, whatever it contains. No weighted credits, no interpretation bundles to pay for.

Free

€0

  • 2,000 charts a month
  • 30 requests a minute
  • All bodies, angles and houses
  • Email support
Get a free key

Developer

€9/ month

  • 25,000 charts a month
  • €0.40 per extra 1,000
  • 120 requests a minute
  • Email support
Choose Developer

Business

€99/ month

  • 1,000,000 charts a month
  • €0.10 per extra 1,000
  • Data processing agreement
  • 99.9% uptime target
Choose Business

Dedicated instance. Your own EU deployment, your own keys and limits, an SLA and a named contact. From €400 a month.

Talk to us

Prices exclude VAT. Annual billing includes two months free. Going over your monthly charts never breaks your app mid-month: calls keep working and we get in touch.

06 — Compare

What you stop worrying about.

Running an ephemeris yourself or picking a bundle API both work. Here is where Skyline saves you time.

Skyline AstroSelf-hosted Swiss EphemerisTypical astrology APIs
Accuracy evidencePublic benchmark, 565 cases, per pointThe reference itselfRarely published
Licence for your appNone neededAGPL, or a paid professional licenceOften unstated
Request dataNever stored, cached or loggedUp to youOften unstated, sometimes cached
HostingEU, BelgiumYour serversOften unstated
Billing unit1 chart = 1 requestYour infrastructureCredits weighted per endpoint
Time to first chartMinutesDays: build, host, maintainMinutes

07 — Questions

Before you integrate.

Why do I send UTC instead of local time?

Historical time zones and daylight saving rules cause most wrong charts. Converting in your app, with the IANA time zone database, keeps that logic where you can test it.

Libraries such as Luxon, date-fns-tz or Python's zoneinfo do it in one line.

Which zodiac and coordinates do you use?

Tropical zodiac, geocentric positions, true ecliptic and equinox of date. Angles are decimal degrees with six decimals, longitudes in [0, 360).

Which date range is covered?

From 1 January 1900 to 31 December 2100, for every body including Chiron.

Do you offer interpretations or horoscopes?

No. Skyline returns astronomy only, so your app keeps full control of signs, aspects, orbs and texts.

What happens if I go over my plan?

Your calls keep working. We see the overage in our monthly report and write to you about the right plan. The per-minute limit protects the service from runaway loops.

Can I run Skyline on my own infrastructure?

The dedicated plan gives you an instance of your own in the EU. Write to us if you need it in another region.

Do you support sidereal zodiacs?

Tropical is available today. Tell us which ayanamsa you need and we will tell you when it ships.

Contact

Building an astrology app? Tell us what it needs.

Volumes, house systems, a dedicated instance or a feature you are missing. You talk directly with the people who build the engine.

Write to us contact@aiprenor.ro

We reply within 24 hours.