StarWatch: Moravian University Astronomy

APRIL 2026

APRIL STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK

lunar phases

1546 APRIL 5, 2026: Jupiter is at Eastern Quadrature: My astronomy professor, Dr. Carlson R. Chambliss, rigorously broadened my knowledge of the heavens when I was a junior at Kutztown University. Since there was only a nine-year difference in our ages and I was his only student in his advanced introductory class, he took a special interest in me, one that burgeoned into a lifelong friendship that continues to this day. Because of our special instructional arrangement and my interests in astronomy, Carlson crammed two semesters' worth of course material into a half term. My mind nearly exploded several times, but he sparked in me an even greater desire to learn more about the cosmos that I loved. * Carlson spent the earliest part of his career working for the Time Service at the US Naval Observatory in Washington, DC, so his mind was filled with all types of details regarding the movements and positions of astronomical bodies. He instilled some of that into my teaching and this blog. However, those bland mathematical equations that were also part of Carlson's lessons in later courses came in handy several years into my professional career. Dr. Charles F. Wilson, Superintendent of Schools in Allentown, tasked me with calculating the precise winter sunrise times in early January for a new bussing schedule the District was considering for adoption. At that time, I was assistant director of the ASD Planetarium situated at Dieruff High School. That learning experience made me realize that all knowledge was important, not just the content you wanted to learn.
Getting back to Jupiter at eastern quadrature... The planets, and all astronomical bodies for that matter, change their positions in the sky for two basic reasons: their own orbital motions and the movements of our observing platform, the Earth. In the case of the planets and our moon, they all revolve in a counterclockwise direction as seen from the vantage point of space looking over the Northern Hemisphere. * As we view the motion of planets from the Earth, they seem to pull away from the sun and then return to it at intervals called their synodic (phase) periods. At certain angular distances from the sun (elongations), names describe these positions. Kindly see the diagram for planetary configurations accessible here. * For superior planets, at greater solar distances than the Earth, (including our orbiting moon), these special positions can be conjunction, in alignment with the sun; opposition, opposite to the sun; or at quadrature, an angle of 90 degrees from the sun. Likewise, inferior planets, closer to the sun than Earth (Mercury and Venus), seem to move from side-to-side of the sun. When an inferior planet passes between the Earth and the sun, astronomers say the planet is in inferior conjunction. When it passes behind Sol on the far side of its orbit, it is in superior conjunction. * Quadrature or opposition will never be terms associated with Mercury and Venus. They will pull away from the sun and reach their greatest elongation from Sol before heading back into the sun's glare. If the position is at its greatest angular extent and the planet sets after sundown, it is at greatest eastern elongation. The inferior planet is as far to the east in the sky as it can travel before orbiting back into the sun's glare. The inferior planet will set after sundown. Likewise, if this angle of greatest elongation is reached in the morning sky, the planet is as far to the west as it can shift, and that angular distance is termed greatest western elongation. The planet rises before the sun. Quadrature for a superior planet is termed as eastern quadrature if the planet is in the evening sky and western quadrature when the planet reaches an elongation from the sun of 90 degrees in the morning heavens. Jupiter is at eastern quadrature on Sunday, April 5, 90 degrees from the sun in the evening sky. Look high in the south, 30 minutes after sundown if it is clear! You cannot miss it. Jove is incredibly bright. Ad Astra!

1547

APRIL 12, 2026: Binocular Comet This Week

Kreutz sungrazer C/2026 A1 (MAPS) disintegrated rapidly on April 4, during its perihelion transit that brought it to a scant 100,000 miles above the sun's surface (photosphere). Had the comet survived intact, we might presently be celebrating one of the great astronomical events of the 21st century. One comet down, one to go. * A more reliable comet, C/2025 R3 PanSTARRS, is predicted to be visible low in the early dawn eastern sky this week as it brightens slowly and travels sunward towards its rendezvous with Sol on April 19. Discovered on September 8, 2025 by the Panoramic Survey Telescope and Rapid Response System (PanSTARRS) located at the Haleakala Observatory, Maui, Hawaii, the Oort cloud interloper is on a hyperbolic orbit, making it a once-and-done visitor to the inner solar system. Comet PanSTARRS is behaving nicely, having been visually first spotted through 10x50 binoculars by Alan Hale (of Comet Hale-Bopp fame) on March 20. Note that Hale lives in an extremely dark location in the Sacramento Mountains near Cloudcroft, New Mexico. His experiences will not be duplicated by our views on the East Coast. The comet is expected to brighten from fourth magnitude at the beginning of the week to third magnitude near its end, so this will be a binocular event if current predictions hold. Your observing site will need to have an excellent eastern horizon. * The map below only shows the location of PanSTARRS about an hour before sunrise. It does not accurately indicate brightness. I would advise being at your observing site a little earlier, perhaps 5:15 a.m. locally. Have patience. If clear skies prevail, a small, fuzzy object with an extension away from the sun, its tail, should become visible. Much success. Ad Astra!

Comet PanSTARRS. Gary A. Becker map using Software Bisque's The Sky...

Venus is rising higher in the spring sky. Gary A. Becker image taken on April 9...

1548 APRIL 19, 2026: Lyrid Meteors, Regulus Occulted, Good Times

1549 APRIL 26, 2026: The Equatorial Coordinate System: We locate positions on the Earth's surface using a system called latitude and longitude. With minor variations, our Earth grid is a reflection of the Equatorial Coordinate System that astronomers use to find objects in the sky. * To refresh your geography lessons, latitude is an angular measurement made from the center of the Earth, beginning at the equator moving to the poles from 0-90 degrees northward or southward along the vertical circle that contains the object, to the object in question. When specifying latitude, it is always necessary to indicate a north or south component, except at the equator. A vertical circle in this situation is a great circle with its center positioned at the Earth's center. It is perpendicular to both horizons and traverses through the zenith. * Longitude is an angular measurement made from Earth's center starting at the location of the equator on the Prime Meridian, proceeding east or west from 0-180 degrees to the vertical circle that contains the object. When specifying longitude, except for 0 and 180 degrees, it is always necessary to indicate whether the location is in the eastern or western hemisphere. Visually on a terrestrial globe, latitude acts like a ladder (up and down) while longitude represents the long circles that intersect both poles. * The Greenwich meridian was chosen as the world's official Prime Meridian at the 1884 International Meridian Conference held in Washington, D.C. where 25 nations voted to adopt it. Britain ruled the seas, and 70 percent of all navigational charts at that time used the Prime Meridian at Greenwich as the zero position for longitude. * Employing this system, the position of Moravian's Sky Deck located on the rooftop of the Collier Hall of Science is 40.6297 degrees North latitude (40 deg., 37 min., 47 sec. N.), 75.383 degrees West longitude (75 deg., 22 min., 59 sec. W.). * We create the equatorial coordinate system by projecting latitude and longitude into space. Here latitude, now called declination, is measured northward or southward from the celestial equator along a vertical circle to the position of the object. Instead of saying north or south declination, astronomers use positive (+) for north and negative (-) for south. It is the longitude component called right ascension, which is slightly trickier. RA, as the term is denoted, begins at the position of the vernal equinox, the location of the sun as it crosses the celestial equator at the first moment of spring. It proceeds only eastward in the direction of the Earth's rotation, normally not as an angle measured in degrees, minutes, and seconds but as a time component measured in hours, minutes, and seconds. The entire system completes a full cycle in 23 hr., 56 min., 4 sec. of clock time equivalent to one rotation of the Earth. However, since the spinning Earth also acts like an accurate clock, astronomers divide the Earth's rotational period, reflected onto the heavens, into a 24-hour sky clock with hours, minutes, and seconds, each with shorter intervals than the 24-hour system our house clocks maintain. This interval is termed the sidereal (star) day. * While very small changes in latitude occur over time, there is a slow secular change in right ascension and declination positions. Over a nearly 26,000-year cycle called precession, the vernal equinox slides westward around the entire sky, taking with it the equatorial coordinate system, changing the positions of all celestial objects in the sky. However, since both systems are a reflection of one another, it is possible to use the positions of the stars in the sky and the time difference between the observer's position and the Prime Meridian to obtain a precise position of an unknown location on Earth's surface. This superiority in navigational skills, particularly in determining longitude, gave Britain mastery of the oceans and led to the phrase the empire on which the sun never sets. Ad Astra!