Photo of the Week for June 7, 2019
As impressive as face-on spiral galaxies are in photographs, they can be challenging to observe in telescopes. Take M101, also known as the Pinwheel Galaxy, for example. It’s nicely situated above the handle of the Big Dipper and can be detected in binoculars under a dark sky. But add even a modest amount of light pollution, and it all but disappears. That’s because the galaxy’s surface brightness—its luminosity per arc-minute of sky—is relatively low. In other words, most of the galaxy is only a little brighter than the background sky. To see M101 in all its glory, a moonless country night sky is a must. But even a large telescope used under ideal conditions won’t show all the features visible in this image.
Greg Polanski recorded this wonderfully detailed M101 portrait on May 5, 2019, from the Dark Sky Preserve in North Frontenac, Ontario, with a Sky-Watcher Black Diamond 150/750 6-inch f/5 reflector telescope (fitted with a Sky-Watcher coma corrector) and a QHYCCD QHY163C imaging camera. The final picture combines a total of 4.1 hours of image data shot through Baader Planetarium RGBL filters.