nsb 0.1.1

Night-sky background evaluation and observation planning for ground-based astronomy.
Documentation 
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// SPDX-License-Identifier: AGPL-3.0-only
// Copyright (C) 2026 Vallés Puig, Ramon
use chrono::{DateTime, Utc};
use nsb::units::radiometry::PhotonsPerSquareCentimeterNanosecondSteradian as BandPhotonRadiance;
use nsb::{ComponentMask, NsbEvaluator, Target, ThresholdQuery, DEG};
use siderust::catalogs::observatories;
use tempoch::{Period, Time, UTC};

fn main() -> nsb::Result<()> {
    let start = parse_utc("2023-09-04T00:00:00Z");
    let end = parse_utc("2023-09-04T12:00:00Z");

    let query = ThresholdQuery::new(
        observatories::EL_PARANAL.geodetic(),
        Target::new(266.41683 * DEG, -29.00781 * DEG),
        Period::new(start, end),
        BandPhotonRadiance::new(0.21),
    )
    .with_components(ComponentMask::ZODIACAL | ComponentMask::AIRGLOW);

    // Practical adaptive discovery has a documented physical-model resolution
    // assumption. Use periods_below_threshold_certified for strict certificates.
    let result = NsbEvaluator::new()?.periods_below_threshold(&query)?;

    println!(
        "threshold = {:.6e} ph/(cm² ns sr)",
        result.threshold.value()
    );
    if result.periods.is_empty() {
        println!("(no sub-periods in window are below threshold)");
        return Ok(());
    }

    println!("{} period(s) below threshold:", result.periods.len());
    for period in result.periods {
        println!(
            "  {} -> {}",
            format_utc(period.start),
            format_utc(period.end)
        );
    }

    Ok(())
}

fn parse_utc(input: &str) -> Time<UTC> {
    let time = DateTime::parse_from_rfc3339(input)
        .expect("valid example timestamp")
        .with_timezone(&Utc);
    Time::<UTC>::from_chrono(time)
}

fn format_utc(time: Time<UTC>) -> String {
    match time.to_chrono() {
        Some(dt) => dt.format("%Y-%m-%dT%H:%M:%S%.3fZ").to_string(),
        None => "<unrepresentable UTC instant>".to_string(),
    }
}