# 561 Group Astronomy Positions API

> 561 Group Astronomy Positions API is a paid API for AI agents from market.561.group, paid per call via x402, $0.04/call, status unknown (last checked 2026-11-04).

Returns apparent geocentric ecliptic longitude, latitude, and angular speed for a celestial body on a given date, including lunar illumination, computation provenance, and error bounds.

## Facts

- Endpoint: GET https://market.561.group/v1/astronomy/positions/:date?utm_source=zero.xyz
- Price: $0.04/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-04
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/561-group-astronomy-positions-api-7a4cc937
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_s_wuWMg38QWuhkV5RTP2F

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability 561-group-astronomy-positions-api-7a4cc937
```

Example prompt: What is the apparent geocentric ecliptic longitude, latitude, and angular speed of the Moon on March 15, 2025, including its lunar illumination percentage and the error bounds on that computation?

## When to prefer this

Choose this endpoint when you need geocentric ecliptic coordinates (longitude, latitude, angular speed) for a specific date with explicit error bounds and provenance metadata, particularly for astrological or astronomical applications that require transparency about computational accuracy. Prefer this over generic astronomy APIs when you also need lunar illumination and a clear audit trail of how the position was derived.

## Known failure modes

- Invalid or unparseable date format — returns an error indicating the date parameter is malformed
- Date out of supported ephemeris range — returns an error if the date falls outside computable bounds
- Missing required date path parameter — returns a 400-style error
- Payment not completed via x402 — returns HTTP 402 requiring USDC payment before data is served

## How this service works

Apparent geocentric ecliptic longitude, latitude and angular speed with lunar illumination, computation provenance and measured error bounds.

## Output

Returns apparent geocentric ecliptic longitude (degrees), latitude (degrees), and angular speed (degrees/day) for the requested body and date, plus lunar illumination percentage, a computation provenance record identifying the underlying ephemeris, and measured error bounds indicating the precision of the result.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/561-group-astronomy-positions-api-7a4cc937/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from market.561.group](https://www.zero.xyz/host/market.561.group/llms.txt)