/**
 * astroengine pheno -- phase, elongation, apparent diameter, magnitude,
 * equation of time, horizontal coordinates, refraction.
 *
 * Magnitude models: Mallama & Hilton 2018 for Mercury-Saturn (Saturn with
 * the ring term), constant-plus-distance for Sun and Pluto, the Mallama
 * secular ramp for Neptune, Allen's phase law for the Moon (valid to phase
 * angle ~140 deg; the Moon is invisible near conjunction anyway).
 * Validated against swe_pheno (Swiss Ephemeris 2.10, Moshier mode).
 */
import { EngineData } from "./core.js";
import { Engine, BodyId } from "./chart.js";
/** Equatorial diameters, km (IAU values, as used by Swiss Ephemeris). */
export declare const DIAMETER_KM: Record<string, number>;
export interface Pheno {
    phaseAngle: number;
    phase: number;
    elongation: number;
    diameter: number;
    magnitude: number;
}
/**
 * Photometric and apparent-geometry quantities for a body at an instant: its
 * phase angle, illuminated fraction, elongation from the Sun, apparent disc
 * diameter, and apparent visual magnitude.
 *
 * @param engine The engine used to evaluate positions.
 * @param body A body with known physical dimensions (Sun, Moon, the planets).
 * @param jdUt Julian Day (UT).
 * @returns A {@link Pheno}: `phaseAngle` (deg), `phase` (lit fraction `0`–`1`),
 *   `elongation` (deg), `diameter` (deg), and `magnitude`.
 * @throws Error if `body` has no photometric data.
 * @example
 * ```ts
 * pheno(engine, "venus", julianDay(2025, 6, 1)).phase; // illuminated fraction
 * ```
 */
export declare function pheno(engine: Engine, body: BodyId, jdUt: number): Pheno;
/** Apparent minus mean solar time, minutes (Meeus ch. 28). */
export declare function equationOfTime(engine: Engine, jdUt: number): number;
/** Apparent ecliptic position -> azimuth (deg, from true north, east-
 *  positive) and true altitude (deg). No refraction. */
export declare function azAlt(data: EngineData, lonDeg: number, latDeg: number, jdUt: number, obsLat: number, obsLonEast: number): [number, number];
/** Saemundsson refraction, degrees. Returns the input unchanged when even
 *  the refracted altitude stays below the horizon (matches Swiss
 *  Ephemeris). */
export declare function refractTrueToApparent(altDeg: number, pressure?: number, tempC?: number): number;
/**
 * Relative optical air mass at an apparent altitude (Kasten & Young 1989).
 * 1.0 at the zenith, ~38 at the horizon; below the horizon the horizon
 * value is returned (the path length stops growing once the ray grazes).
 */
export declare function airmass(altAppDeg: number): number;
/**
 * Atmospheric extinction in magnitudes at an apparent altitude: `k` mag per
 * air mass (default 0.2, a clear-sky visual coefficient; hazy sites run
 * 0.3+). This is the dimming the horizon note describes -- computed, so a
 * render pipeline consumes a number instead of re-inventing the physics.
 */
export declare function extinctionMag(altAppDeg: number, k?: number): number;
/** Bennett refraction, degrees. */
export declare function refractApparentToTrue(altDeg: number, pressure?: number, tempC?: number): number;