The zodiacal light, often referred to as the “false dawn,” presents a unique challenge for astronomers: it is notoriously difficult to distinguish from natural and artificial skyglow. For years, observers have reported that the initial moments of looking for this phenomenon are marked by uncertainty, with the faint glow easily mistaken for distant city lights or the onset of morning twilight. However, under truly dark skies and in long-exposure photography, the structure’s distinct conical shape becomes undeniable.
This week offers one of the year’s best opportunities to witness the event. The new moon falls on September 10-11, eliminating moonlight interference during the predawn hours. The primary obstacles for observers will be familiar ones, including cloud cover, atmospheric haze, and light pollution. The phenomenon itself is caused by sunlight scattering off dust concentrated along the ecliptic plane—the path followed by the sun, moon, and planets. This dust disk is home to the zodiac constellations, giving the light its name, which translates to “light from the circle of animals.”
For those in the Northern Hemisphere near the September equinox, the optimal viewing angle is eastward before morning twilight begins. At this time, the ecliptic rises steeply from the horizon, helping the faint glow separate from the brighter horizon murk. The glow can extend 30 to 40 degrees upward, appearing as a broad, softly glowing pyramid that is often fainter than the Milky Way and lacks hard edges.
Successful observation requires an unobstructed view of the eastern horizon, ideally over a large body of water, and complete darkness. Observers should arrive before astronomical twilight starts, allowing their eyes at least 20 to 30 minutes to adapt to the darkness. Unlike the rounded dome of artificial skyglow, zodiacal light stretches diagonally or nearly vertically along the ecliptic.
Photographers may find it easier to capture the light with the naked eye using a camera. A tripod and a wide-angle lens between 14mm and 24mm are recommended. Initial settings should include an aperture of f/2.8, an ISO of 1600, and exposures lasting 10 to 20 seconds. Shooting in RAW format and focusing manually on a bright star can improve results. Experts advise against repeatedly checking the camera screen, emphasizing that the experience is best enjoyed by observing with the naked eye.
Looking ahead, skywatchers can expect a waxing crescent moon near Venus in the western twilight on September 14. By September 16-17, the moon will move toward Antares in Scorpius. On September 18, the first quarter moon will appear alongside Venus at its greatest brilliancy as the Evening Star.
During predawn hours in September, the constellation Orion will be visible in the east. Although typically associated with winter, Orion’s stars, including its famous belt and Sirius, rise along the ecliptic, offering a preview of the winter sky. Jupiter and Mars will also be visible near the zodiacal light, making this a rewarding period for early morning stargazing.
Leave a Reply