Golden and blue hour windows in Rust

What does a real call return?

For Paris on 21 June 2026, the first blue window runs from 03:04:18 to 03:21:31 UTC and the first golden window from 03:21:31 to 04:36:59 UTC.

Recorded on 2 November 2026 through the public MCP endpoint, service release 0.17.1. Inputs and full responses, response SHA-256 e8a283bcfbc4…. Verdict values are the literal values the tool returns. Run the same inputs yourself to compare; elapsed times vary, and a new release may change the figures.

Checked against

• Stored Skyfield 1.55/JPL DE421 reference days, threshold tangencies, polar/boundary windows and independent azimuth samples.

Recorded on release 0.16.1. These checks cover the listed cases, not every input. Evidence cards.

How it works

A bounded CPU scan refines solar-elevation crossings and extrema, including grazing windows near midnight. Golden elevation is −4° to +6°; blue is −6° to −4°. Window classification follows the solar centre above an ideal horizon without refraction.

Inputs and units

Provide date_utc as YYYY-MM-DDT00:00:00Z (a UTC day, not a local civil day), latitude −89° to 89° and east-positive longitude −180° to 180°. Years 1900–2100 are accepted.

What the result contains

Sorted UTC millisecond windows, durations, midpoint azimuths when defined, rising/setting direction, period-boundary flags, threshold crossings, daily elevation extrema and numerical diagnostics. Paris and Tromsø examples are reproducible.

Example MCP call

{
  "name": "plan_golden_hour",
  "arguments": {
    "date_utc": "2026-06-21T00:00:00Z",
    "latitude": 48.85,
    "longitude": 2.35
  }
}

Send this tool name and arguments through a connected MCP client. Discover the authoritative input schema with tools/list.

Call this engine in one command

Node.js 20+ and npm. This downloads a small remote MCP client; it does not install the engine locally.

npx --yes --package https://scorecompute.com/downloads/scorecompute-call-0.14.2.tgz scorecompute-call plan_golden_hour --arguments '{"date_utc":"2026-06-21T00:00:00Z","latitude":48.85,"longitude":2.35}'

Client download, PowerShell input and verification →

Cite this engine

Version 0.1.0, source SHA-256 444f3168e7ec…. Evidence recorded on release 0.16.1; the public service currently runs 0.17.1. Replace the access date when you cite it.

ScoreCompute. Golden and blue hour windows in Rust (plan_golden_hour), version 0.1.0, source SHA-256 444f3168e7ec20b439d7f0083d9d8fc3f9de14933ec206c2f67cea97dfe971dd. Evidence release 0.16.1, service release 0.17.1. https://scorecompute.com/engines/plan-golden-hour/ (accessed YYYY-MM-DD).

All engine citations · Evidence card

Execution and availability

ScoreCompute exposes this tool through MCP Streamable HTTP. Rust computation runs on a connected worker; the public website and MCP gateway run separately. Among these 22 scientific tools, CUDA is implemented for simulate_pi; the other scientific engines run on CPU. The separate contributor network runs two compiled public workloads: a π estimate and fixed synthetic schedule probes. Requests are bounded and concurrent work may be refused when capacity is occupied.

Record inputs, assumptions and returned provenance when sharing a result. The public observatory displays software client names and tool activity, without publishing calculation arguments or results.