SOLAR ECLIPSE! How it really happens p. 34 The world’s best-selling astronomy magazine MAY 2017 Understanding the strangest stars YEARS OF 50 PULSARS p. 22 DISCOVER 10 WEIRD EMISSION NEBULAE p. 44 Mount Wilson’s famous telescope A short history celebrates a century p. 28 of eclipses p. 49 www.Astronomy.com Image the sky BONUS Vol. 45 with camera ONLINE • Issue 5 and tripod p. 52 CONTENT CODE p. 4 You and Your Shadow... Tele Vue-60 Tele Vue-60 Specifications: Objective: APO Air-spaced Doublet Ap/F.L./f-ratio: 60mm/ 360mm/ f/6 Length OTA: 10” Wherever and Weight OTA: 3lbs. Focuser: 1¼”, push-pull/helical fine focus Whenever You Stroll, Max. Visual Field: 4.3° (with 32mm Plössl/24 Panoptic) Tele Vue-60 OTA shown with optional equipment. Case Dim. 14”x9”x4” Total package weight as shown 5¾lbs. Never Be Without *Solar viewing with any telescope requires proper solar filtering. Your Wanderlust Companion. he August 2017 solar eclipse will be a special few moments in time. The T heirloom quality Tele Vue-60 is designed, built, and tested at Tele Vue for those moments plus all of your future observing adventures. With performance truly beyond expectation, this 4.3° max. true field, diffraction-limited 60mm is no mere toy. The Tele Vue-60 is an observing companion like no other, given its combination of ultra portability and stunning optical fidelity. This petite jewel is Fonemate:smartphone made of black anodized aluminum for lasting beauty and features a buttery- to eyepiece adapter smooth dual stage focuser for that “snap-to-focus” image. Pack its optional custom carrying bag with an Everbrite diagonal, Sol-Searcher, Fonemate, and some Tele Vue eyepieces, grab a Tele-Pod Mount and chase away. Tele-Pod Mount Sol-Searcher For the 2017 eclipse and beyond, your observing time deserves the best. ® Tele Vue 32 Elkay Dr., Chester, NY 10918 (845) 469-4551. televue.com Visionary TV-85 Eclipse Image by Dennis diCicco, processing by Sean Walker. Shot with the EOS 5D Mark IV Camera & EF16-35mm f/2.8L II USM Lens THE EOS 5D Mark IV. A NEW CHAPTER BEGINS. For over a decade, nature photographer Alex Strohl has chosen Canon EOS 5D cameras. It’s a legacy boldly advanced with the new EOS 5D Mark IV. With a 30.4 Megapixel full-frame sensor, built-in GPS and Wi-Fi ® connectivity, and a max ISO of 102400, the features in the Canon EOS 5D Mark IV offer unprecedented flexibility. Perfect for photographers who push the limits. See Legendary. www.usa.canon.com/5D4Legend © 2017 Canon U.S.A., Inc. All rights reserved. Canon and EOS are registered trademarks of Canon Inc. in the United States and may also be registered trademarks or trademarks in other countries. Online Content Code: ASY1705 Enter this code at: www.astronomy.com/code MAY 2017 to gain access to web-exclusive content VOL. 45, NO. 5 ASTRONOMY DON DIXON FOR FOR DIXON DON ON THE COVER Pulsars — incredibly dense, highly magnetized corpses of massive 44 suns — emit beams of intense CONTENTS radiation that sweep the cosmos. FEATURES 22 COVER STORY 36 52 COLUMNS Pulsars at 50: Sky This Month Astroimaging Strange Universe 10 Still going strong Venus dazzles before dawn. without a telescope BOB BERMAN When astronomers initially MARTIN RATCLIFFE AND Do you have a camera? A tripod? stumbled upon these rapidly ALISTER LING Then head outdoors, because Observing Basics 18 pulsing beacons in 1967, you’re ready to image! GLENN CHAPLE they thought they had found ET. 38 MIKE REYNOLDS Secret Sky 20 The truth was almost as shocking. StarDome and STEPHEN JAMES O’MEARA C. RENÉE JAMES 58 Path of the Planets Astro Sketching 64 RICHARD TALCOTT; Great telescopes 28 ERIKA RIX ILLUSTRATIONS BY ROEN KELLY of the past Mount Wilson’s The opticians of yesteryear Binocular Universe 66 combined science and art to pave famous telescope 44 PHIL HARRINGTON the way for today’s masterpieces. celebrates a century Discover 10 weird MIKE REYNOLDS The 100-inch Hooker Telescope, emission nebulae QUANTUM GRAVITY which allowed Hubble to define These clouds of gas, in the 62 Snapshot 8 the size of the universe, was process of gravitationally nearly its builder’s undoing. collapsing into new stars, offer Stellarvue’s Optimus Astro News 12 RONALD L. VOLLER spectacular sights for owners of eyepieces tested medium and large telescopes. Whether you’re observing planets IN EVERY ISSUE 34 or galaxies, this set will make STEPHEN JAMES O’MEARA From the Editor 6 Solar eclipse geometry your current equipment setup What’s happening in space and 49 better. TONY HALLAS Astro Letters 11 on Earth. MICHAEL E. BAKICH; A short history Advertiser Index 68 ILLUSTRATIONS BY ROEN KELLY of eclipses New Products 68 Solar eclipses have been omens Reader Gallery 70 of good or evil, but a few of them have actually changed lives. Breakthrough 74 RAYMOND SHUBINSKI Astronomy (ISSN 0091-6358, USPS 531-350) is ONLINE published monthly by Kalmbach Publishing Co., 21027 Crossroads Circle, P. O. Box 1612, Waukesha, WI 53187–1612. Periodicals post- FAVORITES age paid at Waukesha, WI, and additional offices. POSTMASTER: Send address changes to Astronomy, P.O. Box 62320, Tampa, Fla. 33662-2320. Go to www.Astronomy.com My Science Trips and Seasonal News Canada Publication Mail Agreement #40010760. for info on the biggest news and Shop Tours Observing The latest observing events, stunning photos, The perfect gift Travel the world Find great updates from for your favorite with the staff targets in the the science and informative videos, and more. science geeks of Astronomy winter sky the hobby 4 ASTRONOMY • MAY 2017 Super eyes for the night sky $189.00 2.1×42 wide-field binoculars » Star-field binoculars, allowing you to identify entire constellations » Luminous - 42 mm aperture and 2.1x magnification » Large field of view at 26° 50354 Enter the product number in the search field. The new Sky-Watcher Stargate truss-tube Dobsonians are the biggest thing to happen to the astronomy market in quite some time. Available in 18- and 20-inch models, standard and GoTo, these are the largest mass-market Dobsonians available anywhere. More on... For a complete list of www.Omegon.com specifications and features, please go to www.skywatcherusa.com/ stargate. » Omegon is one of Europe’s leading ©2017 Sky-Watcher USA. Specifications subject to change without notice. 20-17002. We’ve got some more surprizes at our booth at NEAF this year. Just go to our web site or Facebook page to check it all out. astronomy brands - now available in the US! » Shipping starts at only $4.90! Omegon is a section of nimax GmbH. You will find more information about our company at www.nimax.de. Prices Don’t forget to follow us on Facebook and Twitter! are subject to change and errors are excepted. WWW.ASTRONOMY.COM 5 FROM THE EDITOR BY DAVID J. EICHER Editor David J. Eicher Art Director LuAnn Williams Belter EDITORIAL Managing Editor Kathi Kube Senior Editors Michael E. Bakich, Richard Talcott Associate Editors Alison Klesman, John Wenz Copy Editors Dave Lee, Elisa R. Neckar An astronomical Editorial Assistant Nicole Kiefert ART Graphic Designer Kelly Katlaps Illustrator Roen Kelly workhorse Production Coordinator Jodi Jeranek CONTRIBUTING EDITORS Bob Berman, Adam Block, Glenn F. Chaple, Jr., Martin George, Tony Hallas, Phil Harrington, Korey Haynes, Jeff Hester, Liz Kruesi, Ray Jayawardhana, Alister Ling, Steve Nadis, Stephen handful of instru- On October 4, he took a Hubble had used the James O’Meara, Tom Polakis, Martin Ratcliffe, Mike D. ments stand out as 40-minute exposure, despite workhorse 100-inch Hooker Reynolds, Sheldon Reynolds, Erika Rix, Raymond Shubinski all-time champions worrying over somewhat scope to discover the nature EDITORIAL ADVISORY BOARD Buzz Aldrin, Marcia Bartusiak, Timothy Ferris, Alex Filippenko, in the history of poor seeing, with the result- of galaxies, and break open Adam Frank, John S. Gallagher lll, Daniel W. E. Green, William K. Hartmann, Paul Hodge, Anne L. Kinney, Edward Kolb, astronomy. The ing turbulent star images. the cosmic distance scale. Stephen P. Maran, Brian May, S. Alan Stern, James Trefil A200-inch scope at Palomar, Nonetheless, he developed And there was much more the refractors at Lowell and the glass plate negative and to come. Kalmbach Publishing Co. Yerkes, and the “Leviathan examined it carefully. He On another note, I’m Senior Vice President, Sales & Marketing Daniel R. Lance Vice President, Content Stephen C. George of Parsonstown” in Ireland found something exciting, a delighted to welcome two Vice President, Consumer Marketing Nicole McGuire come to mind. But none suspected nova — an new staff members to Corporate Art Director Maureen M. Schimmel Art and Production Manager Michael Soliday played a more significant role exploding star. Astronomy. Associate Editor Corporate Advertising Director Ann E. Smith in deciphering the structure The next night he imaged Alison Klesman brings a Single Copy Specialist Kim Redmond ADVERTISING DEPARTMENT of the universe than the the spiral nebula again, solid scientific background (888) 558-1544 100-inch Hooker Telescope at believing he had better see- along with her writing and Advertising Sales Manager Steve Meni Advertising Sales Representative Mount Wilson Observatory ing and might have a supe- editing skills; she has a mas- Dina Johnston, [email protected] Ad Services Representative near Los Angeles. And this rior image. The famous plate ter’s degree in planetary sci- Christa Burbank, [email protected] year, the Hooker scope cele- he recorded that evening ence from the Massachusetts RETAIL TRADE ORDERS AND INQUIRIES brates a century of existence. would become one of the Institute of Technology and a Selling Astronomy magazine or products in your store: Phone (800) 558-1544 Science writer Ron Voller greatest ever made.