Abstract: An instrument is provided which requires no complex computations or high degree of skill in aligning scales to accurately indicate the time of day from observations of the position of the sun, and to accurately locate the moon, the sun, and other stars and constellations in celestial space.The instrument comprises a vertically adjustable stand upon which is mounted a support plane which may be rotated about a horizontal axis to accommodate alignment with the celestial equator. To the support plate is mounted a single rotary disk rotatable about a principal axis normal to the plane of the support plate. Inscribed upon the surface of the disk are an hour scale, a month-day scale, a right ascension hour angle scale, a local hour angle scale, a moon phase scale, a lunation scale to trace the phases of the moon, and a zodiac constellation display.