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Mu (μ) Draconis – doubling up on Dragon Eyes

Mu (μ) Draconis (Alrakis)

RA: 17h 05m   Dec: +54° 28′
Mag: 5.7, 5.7   Sep: 2.3″   PA: 14°
Dist: 88  ly
Spectral Classification: F7

I love this pair! They looked like a couple of bowling balls rolling down my field of view and being perfectly matched they are a very close version of the beautiful binocular double, Nu (ν) Draconis. What’s more, there was a nice lesson in here for me, since I  compared my experience with them with my experience with Epsilon (ε) Draconis. And the day after I posted this I discovered the Dragon has yet a third sat of eyes! They are 16-17 Draconis and I’ll treat them in a separate post.

What I found with Epsilon(ε) was that even though they were wider apart – 3.2 seconds for Epsilon (ε) vs. 2.3 for Mu (μ) – I could split  the closer pair, Mu(μ), easily with the 76mm – and Sissy Haas says its easy with a 60mm! – and yet I needed the 127mm scope to split Epsilon (ε)! Why? Because of the difference in magnitude between primary and secondary. Now this is really not news to an experienced double star observer – but it’s always nice to see theory borne out in practice.  With Epsilon (ε) you get a difference of almost three magnitudes – with Mu (μ) there is simply no difference! Stars of the same brightness are much easier to split than stars where the primary is brighter than the secondary.

Finding Mu (μ) presented a challenge for me because I had a nearly full moon behind me. I could not spot Mu (μ) with my naked eye. In fact, I couldn’t spot Nu (ν) – at 4.9 nearly a full magnitude brighter – with my naked eye, but because it’s the dimmest corner of the Dragon’s head it’s relatively easy to find – and it’s absolutely unmistakable in binoculars or a small finder – two 4.9 magnitude stars split by 63.4″ – a full  minute and then some. So Nu (ν) was my jumping off point to Mu (μ). Sort of like going from daddy dragon to baby dragon! It also happens to be almost on the same declination circle as Mu  (μ)- Mu (μ) is at 54°28′ and Nu (ν) is at 55°11′. So I got Mu (μ) in view with my widest eyepiece – about a degree – and shifted it over to the north side of that eyepiece. I then locked the declination axis on the equatorial mount and panned in right ascension until a bright star came into view – that’s a short trip as well because  Nu (ν) is at RA 17h 32m and Mu (μ) is at 17h 5m. I popped in a 10.2mm eyepiece and could see I had a double – but unsplit. So i went to the 6-2 Nagler zoom. At 6mm (200X) it split – at the 5mm click stop (240X)  it was even better.

Now Haas says “They are just bright enough to be easy with a 60mm.”  On a better night I’ll put that to the test. She also says they “are almost fully split with 120X.” Uh huh. So what exactly did she split it with? Because 120X is really pushing the limits of a 60mm scope. I guess I’m really not sure what “almost fully split” means? For me, “split” means so you can see dark sky between the stars.Anything less than that isn’t a split. So now I’m really curious about giving this  a go with a 60mm.  Meanwhile, I took a break in writing this report to do a little observing with a 100mm F6 Orion – and I tested it’s optics on Mu which was getting fairly low in the west – and I split it. Good optics for an inexpensive and pretty fast (f6) achro! I think I’ll be coming back to this pair frequently.

(Bonus – if you don’t know your Greek alphabet yet, just reread the paragraphs above – no matter how long I deal with them, Mu (μ) and Nu (ν) haunt me. But I may have gottenthe confusion out of my system by writing this – or made it worse.  🙂


5 Responses

  1. Well, now, Greg, you’ve aroused my curiosity – I’m familiar with Nu, but Mu is brand new! (sorry about the pun).

    As soon as this November-like stretch of cloudy weather goes away, I’ll get a 60mm scope out and see if I can split this pair. Klaus says he can do it, too, so don’t be surprised if you soon see a photo of him at the scope, an eyepiece in one paw and a Milk Bone in the other. He’s partial to the 76mm, though.

    To be continued ………………

    • August 16th, 2010

      Sacre Bleu!
      What’s a Star Splitter to do?
      The CSC squares are all blue,
      But the whole sky is full of dew!

      I guess I can laugh … but this is getting monotonous. Yes, I said I would be back – just didn’t think it would take quite this long. Four weeks of fog, clouds, fog, clouds, and one clear night that was so turbulent I could barely split Mizar.

      However … I did get an hour of good observing in before the fog put me out of business once again. Although it was perfectly clear at 9 PM, by 9:15 a halo of fog tried to gobble up the moon, so I knew I had to move quickly. And I knew I was in trouble when I could see very fine beads of moisture hanging in the air in the beam of my red flashlight – red beads, at that.

      I used the Zeiss 63/840 because I wanted to look at Mu, 16-17, and Epsilon Draconis. I got the first two, anyway! The seeing was very good for the short time it was clear. I had an 18mm Radian (47x) in the scope as I was lining it up on Polaris, and then I replaced that with an 8mm Radian (105x) to see how steady the seeing was. Somehow I forgot that was in the eyepiece, and when I swung the scope to Mu Draconis, I about fell out of the chair when I saw two stars! I pulled the flashlight out to look at the eyepiece because I couldn’t believe that would happen with an 18mm – and of course, there was the green lettering of the 8mm grinning at me. Anyway, it was way too easy — but that’s what good seeing can do for you!

      Then I moved the scope down to 16-17 Draconis, this time with a 12mm Radian (70x) in it, and sure enough, I had a very tight pair, but split – just barely. I swapped a 10mm Radian (84x) into the diagonal and had a very clean split, as was the case with the 8mm. This is a beautiful triple system – I could get hooked on it. Mu is a delight, too – as Greg wrote above, it looks like a very tight version of Nu Draconis, aka “the Eyes.”

      You gotta take what the sky gods give you – and it was a very satisfying hour, I’ve gotta admit.

      And Klaus says, “WOOF!”

  2. Yes you can – you can split it with a 60mm, though I’m not sure I would call it easy and for me it was anything but easy. However, 95% of my frustration was with the mechanics of mounts and telescope as I frittered away excellent observing conditions. I won’t dwell onthat. Thebottom line is this: With a 76mm Tasco it split beautifully – better than the first time because ocnditions were better – the air more stable. That encourage dme to go get the little Unitron and give it a try. I got a clean split with a 7.2mm Plossl (125X) and an even better split with 6mm Nagler zoom (150X). More power didn’t improve the view.

    I’m wondering if John or anyone else sees any color here? The stars are described as the same by others, but one seems significantly yellow to me while the other seems more white or even very pale blue.

    • Oh – btw – I found it with the dinky little finder that’s standard for the Unitron 114 after my sweeping the area with a low power eyepiece failed to turn it up. It’s really pretty isolated, so easy to pick up.

  3. Spent a lot of time here last night finding these three without a finder on the 110mm. (It’s in the mail!) But I wanted to commit the process to memory – moving from Nu (ν) to Mu (μ) to 16-17. It’s two steps west and half a step south. That aside, this experience confirmed that the real showcase of the three is Mu. The other pairs are two wide to provide much excitement in a telescope. True, the secondary split ( I think it’s 17) is nice, but the pairs aren’t the same brightness. So the gold medal goes to Mu, but all remain fun and I expect to be back many times, showing these to visitors.

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