August 17, 2018

24.9.9; “Anti”Crepuscular Rays!

Sometimes near-sky astronomy happens during the strangest of moments. Over the past week, we’ve been treated along the Florida Gulf Coast to some fine displays of crepuscular rays during sunrise and sunset. Generally these shining rays can be seen streaking through the crags and valleys of mountain ranges and ridges when the Sun is at a low angle. In the “flatland” of Florida, however, these occur for a different reason; scattering of sunlight through the edges of large, fluffy cumulus clouds. Humidity, dust and sun angle can all make for a swiftly evolving scene. This mornings’ display from Astrogyuz HQ in Hudson, Florida was one of the best I’ve seen, and even included what’s loosely termed “anti”- crepuscular rays, or rays streaming opposite to the direction of sunrise and seeming to converge towards an imaginary vantage point in the west. This is a fine example of an optical illusion; our minds tend to project the sky as a big, upside down bowl above us, and hence especially long or bright striped rays can actually appear to converge opposite to the Sun!