September 2015 Digital Extra B ON US WE B CONTE NT Photo Gallery E XPLORE O UR WE B S ITE! * Track Triton * Look Up Tonight * Spot Elusive Moons * Astro Community Use our online tool to help you spot Neptune's brightest and biggest moon. Explore new perspectives of the night sky with S&T blogger Bob King. Tell apart Uranus's four largest moons with our online tool. * How to Make Perytons Read more about the mysterious radio signal with a human provenance. Image by Alessandro Carovana Find a planetarium, astronomy club, or observatory near you. * DIY Astro Projects Telescope Tutorials Find advice on tuning up your scope, building a backyard observatory, and more. OBSERVING HIGHLIGHTS TOUR THE SKY - ASTRONOMY PODCASTS Sign up for Newsletters and AstroAlerts THIS WEEK'S Sky at a Glance D OWNLOAD O UR APP S eBook For Droid D I GITAL BAC K I S S UE S: June, July, and August September 2015 sky & telescope ONLINE PH OTO GALLE RY Find us on Facebook & Twitter Jeff Donaldson took a series of exposures to compile this H-alpha filtered image of the Whirlpool Galaxy (M51).http://www.skyandtelescope.com?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-pictures?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-pictures?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/skytel http://www.skyandtelescope.com/skytel http://www.skyandtelescope.com?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/skytel http://www.skyandtelescope.com/skytel http://www.skyandtelescope.com?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-telescopes-triton-tracker/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-telescopes-triton-tracker/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-telescopes-triton-tracker/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-telescopes-triton-tracker/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-telescopes-triton-tracker/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-telescopes-triton-tracker/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-telescopes-triton-tracker/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-telescopes-triton-tracker/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/the-elusive-moons-ofuranus/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/the-elusive-moons-ofuranus/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/clubs-organizations/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/clubs-organizations/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/the-elusive-moons-ofuranus/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/the-elusive-moons-ofuranus/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/clubs-organizations/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/clubs-organizations/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/the-elusive-moons-ofuranus/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/the-elusive-moons-ofuranus/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/clubs-organizations/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/clubs-organizations/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/the-elusive-moons-ofuranus/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/the-elusive-moons-ofuranus/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/clubs-organizations/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/clubs-organizations/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.shopatsky.com/choosing-using-and-equipping-your-telescope?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.shopatsky.com/choosing-using-and-equipping-your-telescope?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-equipment/equipment-diy/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/microwave-ovens-spark-radio-signals-peryton-05122015/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/observing-news?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/observing-news?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-podcasts//?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-podcasts//?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/observing-news?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-news/observing-news?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-podcasts//?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/astronomy-podcasts//?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/newsletter/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/newsletter/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/newsletter/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/newsletter/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.shopatsky.com/summer-deep-sky-ebook?utm_source=nxtbook.com&utm_medium=referral&utm_campaign=sky-mya-toc-150706 http://www.shopatsky.com/summer-deep-sky-ebook?utm_source=nxtbook.com&utm_medium=referral&utm_campaign=sky-mya-toc-150706 http://www.skyandtelescope.com/observing/sky-at-a-glance/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/observing/sky-at-a-glance/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://itunes.apple.com/us/app/jupitermoons/id577009038?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://itunes.apple.com/us/app/jupitermoons/id577009038?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://itunes.apple.com/us/app/saturnmoons/id606938707?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://itunes.apple.com/us/app/saturnmoons/id606938707?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://itunes.apple.com/us/app/skyweek-plus/id541708339?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://itunes.apple.com/us/app/skyweek-plus/id541708339?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://play.google.com/store/apps/details?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://play.google.com/store/apps/details?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.skyandtelescope.com/online-gallery/m51-hargb/?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.facebook.com/pages/Sky-Telescope-Magazine/66274830772?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.facebook.com/pages/Sky-Telescope-Magazine/66274830772?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.twitter.com/#!/SkyandTelescope?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.twitter.com/#!/SkyandTelescope?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.facebook.com/pages/Sky-Telescope-Magazine/66274830772?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.facebook.com/pages/Sky-Telescope-Magazine/66274830772?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.nxtbook.com/nxtbooks/newtrack/st_201506?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.nxtbook.com/nxtbooks/newtrack/st_201506?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.nxtbook.com/nxtbooks/newtrack/st_201507?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.nxtbook.com/nxtbooks/newtrack/st_201507?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.nxtbook.com/nxtbooks/newtrack/st_201508?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 https://www.nxtbook.com/nxtbooks/newtrack/st_201508?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.twitter.com/#!/SkyandTelescope?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15 http://www.twitter.com/#!/SkyandTelescope?utm_source=GD&utm_medium=di&utm_campaign=GDstdiSeptember15