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import type { EquatorialCoordinate, GeographicCoordinate, HorizontalCoordinate } from './common';
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type Q = EquatorialCoordinate & {
    /**
     *
     * The Q index is a measure of the quality of the an observation, which takes into account the
     * illumination of the Moon, the altitude of the target, and the altitude of the Sun as well as
     * the angular separation between the Moon and the target.
     *
     * The Q index is a value between -1 and 1.
     *
     */
    Q: number;
    /**
     *
     *
     * The Moon's illumination factor, which has a range of 0 to 100 percent.
     *
     */
    K: number;
    /**
     *
     * Angular separation between the Moon and the target, which has a range of 0 to 180 degrees.
     *
     */
    φ: number;
    /**
     *
     * The altitude of the target, which has a range of -90 to 90 degrees.
     *
     */
    A: number;
    /**
     *
     * The altitude of the Sun, which has a range of -90 to 90 degrees.
     *
     */
    alt: number;
};
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export declare const q: (K: number, φ: number, A: number, sun: HorizontalCoordinate, moon: HorizontalCoordinate) => number;
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/**
 *
 * getQIndex()
 *
 * @brief The Q index is a measure of the quality of the an observation, which takes into account the
 * illumination of the Moon, the altitude of the target, and the altitude of the Sun as well as
 * the angular separation between the Moon and the target.
 *
 * @param datetime - The date and time of the observation.
 * @param observer - The geographic coordinates of the observer.
 * @param target - The equatorial coordinates of the target object (at J2000.0).
 * @returns The Q index of the observation, a value between -1 and 1.
 */
export declare function getQIndex(datetime: Date, observer: GeographicCoordinate, target: EquatorialCoordinate): Q;
export {};
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