Saskatoon Skies The Newsletter of the Saskatoon Centre of the Royal Astronomical Society of Canada Volume 33 January 2002 Number 1 Observing double stars is fun. My article on page 13 describes the basics of double star terminology
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Starshine 3* Evening Passes – January 16 to February 21
* The purpose of the Starshine 3 project “…is to encourage student around the world to participate in an actual space mission. The spacecraft is like a large disco bass with many small mirrors which glint in the sunlight as the spacecraft rotates and make it visible to observers on the ground. …In addition to the optical tracking, Starshine 3 also carries an amateur radio payload which broadcasts the current satellite spin rate” For more information, visit the project website at http”//www.azinet.com/starshine/. Iridium Flares (> mag. –2) Evening Passes from Saskatoon – Jan. 16 to Feb. 21.
A Double Star Primer By Rick Huziak Observing double stars is just a lot of fun. There are a number of very nice pairs in the sky, and you often chance on double stars near or within most objects you star hop to or observe. You can observe double stars just for the fun of it, or you can also get into precisely measuring the separation of these stars for scientific study. This articles deals more with the basic terminology of double star observing. A double star is a term for two stars that are seemingly close in the sky. There are 2 main categories to double stars: binaries, which are gravitationally connected and rotate around each other, and optical doubles, which seem close together but are in reality just lined up in the sky and may be light years apart in reality, having no real physical association. Multiple stars are just double stars with more than one companion. As in double stars, each companion may be gravitationally associated, or it may be completely non-associated. The fun of observing doubles comes from two places. First, double stars often let you compare the colours of the stars against one another. All stars have some sort of colour, but these colours seem more pronounced when the stars are found in pairs. Secondly, doubles can be used to test sky conditions or optical performance using the two stars’ separation. Separation is the distance from one star to another, and this is always expressed in seconds-of-arc. Close separations are difficult to resolve in smaller scopes or under poor sky conditions. Exactly how close of a double can be separated will be based on your telescope’s quality, the quality of the sky, and by your observing experience. The other attribute that a double star has is position angle. This is a measurement of the angle in the sky that the dimmer star is away from the brighter star. This is measured in angular degrees, with north being 0 degrees, east being 90 degrees, south 180 degrees, and west 270 degrees. The separation and position angle are always measured to the secondary (dimmer star), using the primary (brighter star) as the zero position. Lastly, double stars come in all magnitudes as so all other stars. Close doubles are easiest to separate if the magnitudes of each star are similar, and hardest if the magnitudes are markedly different. So, a complete description of a double star may be: a blue primary, 4.6 magnitude and yellow secondary, 8.4 magnitude, separation 12”, position angle 112 degrees. Double stars are denoted on star atlases as a dot with horizontal line through it. Most atlases show double stars using this symbol. Doubles also have names, and there are several catalogues of double stars, with the designations named (generally) after the observer who discovered them. Common double star names are Burnham, Aitkens, Struve and many others. Probably the most complete double star listing is the Washington Double Star Catalogue, found at http://ad.usno.navy.mil/proj/WDS/wds.html; a compilation which contains thousands of entries, most of which are in dire need of being remeasured. Many of these doubles have not been remeasured since their initial discovery a half-century or century ago! Doubles are measured using a tool called a Filar Micrometer, which fits on an eyepiece and measures separation and position angles. Modern double star observers now have converted to using CCD cameras and sophisticated software to automatically measure these star separations. Only by making continuous observations over many years can it be distinguished whether a double star is a binary or an optical double. A great list of double stars is printed in your 2002 Observer’s Handbook on page 239. Messier, FNGC, H-400 & Binoc Club MESSIER CLUB Certified at 110 Objects: R. Huziak, G. Sarty, S. Alexander, S. Ferguson, D. Jeffrey, D. Chatfield, R. Christie, K. Noesgaard, Mike Stephens Bill Hydomako 78 Wade Selvig 71 Mike Oosterlaken 68 Andrew Krochko 42 Lorne Jensen 44 Brent Gratias 39 Stan Noble 28 Tyrone Klassen * NEW * 26 Les & Ellen Dickson 20 Debbie Anderson 17 Brian Friesen 15 FINEST NGC CLUB Certified at 110 Objects: R. Huziak, D. Jeffrey, G. Sarty, D. Chatfield Scott Alexander 89 Mike Stephens 42 Ken Noesgaard 24 Sandy Ferguson 23 Mike Oosterlaken 15 HERSCHEL 400 CLUB Certified at 400 Objects: Dale Jeffrey, Rick Huziak Darrell Chatfield ** ALMOST THERE** 381 Gordon Sarty 171 Scott Alexander 98 Mike Stephens * NEW * 59 Ken Noesgaard 44 Mike Oosterlaken 44 Sandy Ferguson 18 Chatfield BINOCULAR CERTIFICATE Certified at 40 Objects: Mike Stephens Mike Oosterlaken 32 Join the Messier, Finest NGC, H-400 & Binocular Club! Observe all 110 Messier, 100 FNGC or 400 H-400, or 40 Binocular objects and earn your CERTIFICATES! The first 2 lists can be found in the Observer’s Handbook. The Binocular List & Herschel 400 list will be available at each general meeting for 50 cents (covers photocopying) or can be mailed out on request to distant members. Each month I’ll be posting updates. Hey, Observers! I’ve had updates from several observers this month. With the nice weather, several members are taking the opportunity to tweak up their numbers. Updates were received from Lorne Jensen, Bill Hydomako, Darrell Chatfield, Tyrone Klassen and Mike Stephens! Bill takes over first place in the Messier race. Mike gets added to the H-400 list! Tyrone gets entered into the Messier list. It’s great to see more observing going on! But that is still not enough! I’d like to see every member of the Saskatoon Centre on one of these lists! It’s easy. A few months ago, I mentioned Messier objects visible to the naked eye. Go outside – look at M45 & M31 with your eyes and get yourself started in the Messier Certificate program. Send observing numbers to huziak@SEDSystems.ca Notice of the General Meeting of the Saskatoon Centre Monday, Jan. 21, 2002 at 7:30 p.m. Room 8313 City Hospital Presenting Gord Sarty: The Rare Eclipse of OW Gem Rick Huziak: The New Uranometria 2000.0 Star Atlas Note: there will be an executive meeting this month. U of S Observatory Hours The U of S Observatory is open to the general public every Saturday in January - February from 7:30 p.m. to 9:30 p.m. Admission if free. The observatory is located on campus, one block north of the Wiggins Avenue and College Drive entrance. On clear evenings visitors may look through the 6-inch refractor to the moon, star clusters and other exciting astronomical objects. For further information, phone the recorded Astronomy Information Line at 966-6429. Interested in Saskatoon RASC Membership? Regular - $52.00 per year Youth - $27.50 per year It’s never too late to join! The Saskatoon Centre operates on a one-year revolving membership. You will now be a member for the next 12 months no matter when in the year you join. Benefits of Membership in the Saskatoon Centre
Minutes of the Executive Meeting – December 17, 2001Held in Room 8313, City Hospital Recorded by al Hartridge, Secretary
Minutes of the General Meeting – December 17, 2001Held in Room 8313, City Hospital Recorded by al Hartridge, Secretary
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