by Jim Havlice
Call it what you will: a fad, an obsession, a rite of passage. The “it” is the drive to see lots of deep space objects (DSOs) – in my case Messier Objects. In fact, I have begun a project to see all the Messier objects, recording in my log the date and time that I “bagged” one of sometimes elusive DSOs. The project gives structure to my night time viewing. Rather than dashing off randomly, I have a plan of action, a set of goals for the evening.
But DSO hunting requires a dark sky. Those “dim fuzzy things” are hard to find when the moon is shining brightly. Earlier in the year, I would put away the telescope and wait for a new moon. But the warm evenings of August drew me out and I lugged my trusty ETX 125 MAK out onto the driveway to enjoy – what? The first evening, I “explored” the waxing crescent moon. Well, it’s right there, bright as can be. And it was fun – I found myself lingering over details, like craters within craters. The moon is great for testing your optics at high magnification. I cranked the ’scope up to about 300x. But, your mount better be steady and your hand light on the focuser.
The next night was again warm and the moon larger and higher in the sky. I decided to spend an hour or so looking at stars – double stars, in fact. Strange, isn’t it, that we call ourselves the Mt Shasta Stargazers, but we (or at least I) spend so little time looking at stars? We search for star clusters, nebula, galaxies, planets, and moons. Stars are often last on the list of things to look at! I placed the ’scope so the moon was hidden behind some tall pine trees – trees that often block DSOs, but now serve a useful purpose of avoiding the direct bright light of the moon.
Stars are a great choice in a moonlit night sky. Most are bright enough to “punch through” the moon glow. In fact, if my experience is valid, the varied colors of the stars are more evident with a brighter background.
Just before our first star party, one of our club members (Emily) suggested Albireo as a great double star for the group to view. Albireo is easy to find – it’s the head (or neck or eye) of the “Swan” in the constellation Cygnus. Or, if you prefer, it’s the bottom of the Northern Cross with Deneb at the top. Deneb, Vega, and Altair form the “summer triangle.”
Double Star Albireo in Cygnus
Albireo is also quite easy to “split.” Even a small telescope will show the two stars and the beautiful color difference between them. Albireo is approximately 380 light years away from the Earth. These two nuclear balls of fire are comparatively far from each other and take about 75,000 years to complete a single orbit.
Another easy double, both to find and observe, is Mizar, the second to last star in the handle of the Big Dipper.
Mizar and Alcor in the handle of the Big Dipper
Even binoculars will show Mizar with its companion star Alcor. In a telescope at 75 power, Alcor and Mizar appear to be so far apart that it can be hard to associate the two as part of the big dipper handle. The stars in Albireo are separated by about 35 arc seconds; Alcor and Mizar are separated by almost 12 arc minutes! (There are 60 arc seconds in 1 arc minute). But wait! Mizar itself is a double star – Mizar A and Mizar B. These two stars are separated by about 14 arc seconds. So, you may need to crank up the magnification to see the two Mizar components, but you should certainly be able to see them. Amazingly, both Mizar A and Mizar B are each a double star! So, there are actually FOUR stars in the Mizar system. Forget about seeing these doubles – they are too close to be resolved with our amateur ’scopes.
I wasn’t looking for a challenge. But one found me! After easily viewing Albireo and Mizar, I turned my attention to epsilon-Lyrae, the famous “Double – Double” near the bright star Vega, now directly overhead in our clear August sky. The first problem was that epsilon-Lyrae is not listed on any of the “Go-To” name lists on my Meade Autostar – the computer that controls the telescope. Oh, oh. This writer has become very spoiled (lazy?) by the ease of finding objects using this “Go-To” computer. Now I would have to find the star “the old fashioned way!” Still, with the star so close to Vega, how hard can it be?
Location of the "Double-Double" Epsilon Lyrae near Vega
Extend your arm and place the right side of your index finger on Vega. Epsilon Lyrae should be very close to the left side of your finger. That’s the theory. But in the fairly bright moonlit sky I had trouble seeing the star at all. It didn’t help that Vega is almost straight overhead. The telescope has a right angle mirror that makes viewing easy. But the finder does not – and that means looking up in a very uncomfortable position trying to find the star. The finder is one of those “red dot” pointers with a coated glass plate that you look through. The glass plate diminishes the light enough so that, even when I thought I detected the star with my bare eyes, I couldn’t see it through the finder. I have a new-found appreciation for those of you without a “Go-To” ’scope who find those “faint fuzzies” on your own!
Eventually, I stumbled onto the double. At least I’m pretty sure it was the double. The two major components are separated by about 3.5 arc minutes – a very easy split.
The famous "Double-Double" star epsilon-Lyrae
But the double associated with each component are separated by only 2.3 to 2.6 arc seconds. I was about to crank up the magnification to see if I could split the stars when I noticed the image degrading. A quick look showed drops of dew forming on the front corrector plate. Splitting the double double should be possible with my telescope. My ’scope has a theoretical angular resolution of 0.9 arc-seconds – so the stars are separated by about 2.5 times the resolution limit. But splitting will require clean, dew-free optics. Even a turbulent atmosphere can cause problems (the average size of a turbulent cell is about 1 arc second.) So, I stopped for the evening.
The next night I tried again. Forgive me, but I cheated! During the day I looked up the SAO (Smithsonian Astrophysical Observatory) number for epsilon-Lyrae (SAO 67310), entered the number into the Meade Autostar computer and hit GoTo. In just a few seconds I was staring at the double! My neck thanked me. At 73x magnification I couldn’t split the stars. Changing to 125x magnification, the stars seemed elongated, but definitely not split. Maybe the “seeing” wasn’t very good again. It probably doesn’t help that my driveway is asphalt and warms up considerably during the day. The heat radiating off the surface could cause enough problem turbulence to obscure the split.
I am looking forward to the next star party where I won’t have any “asphalt” excuses. Perhaps one or more of the other telescopes there will try to split the “Double-Double”.
Even when the moon is shining brightly and those pesky “dim fuzzies” are obscured, explore the beauty of the great balls of fire.
Enjoy your night skies.
Epsilon lyra was used by the ancient Arabs, esp the Hejazis as a test of vision. If you saw two stars, you could be an archer of high status. Or, you were judged worth training.
Perseids were a bit of a dud this year due to high thin clouds, plus a bit of moonglow from last quarter moon below horizon. Maybe next year.
Jim; Could you post the meeting calendar on this site? I’d love to join the next meeting! ~Paul