Noctilucent Clouds Over Frankfurt, Germany
August 03, 2017
Photographer: Oliver Stiehler
Summary Authors: Oliver Stiehler; Jim Foster
The photo above shows noctilucent clouds above a foggy field as observed from near Frankfurt, Germany, on June 18, 2017 (taken at 3:30 a.m.). During late spring through midsummer noctilucent (night shining) clouds sometimes form in the mesosphere, at an altitude of about 50 mi (80 km). The tiny particles that water vapor condenses around are thought to be of meteoric origin. Temperatures in the mesosphere are lowest (about -120 degrees C or 150 Kelvin) during the season when the Sun is highest in the sky. Once these clouds form, the Sun must be positioned between 6 and 16 degrees below the horizon for them to be seen. Note that at Frankfurt's latitude, near the summer solstice, the night sky is only dark for several hours -- sunrise in mid-June is approximately 5:15 a.m.
Photo Details: Camera Maker: SONY; Camera Model: ILCE-7RM2; Lens: 85mm F1.4 DG HSM | Art 016; Focal Length: 85mm (35mm equivalent: 85mm); Aperture: ƒ/4.0; Exposure Time: 2.000 s; ISO equiv: 500; Software: Adobe Photoshop Lightroom 6.10 (Windows).