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16 and 17 Draconis – Twin to the famous Dragon’s Eyes plus more

16, 17 Draconis
RA: 16h 36m Dec: +52°55′
Mag: 5.4, 5.4 Sep: 90″ PA: 196°
Distance:  400 ly
Spectral type: B9.5, B9

17 Draconis
RA: 16h 36m Dec: +52°55′
Mag: 5.4, 6.4 Sep: 3″ PA: 196°
Distance:  400 ly
Spectral type: B9.5, B9


These two – 16 and 17 – are an easy binocular pair – and as such a nice warm up for the more challenging (and half a magnitude brighter)  binocular double  Nu (ν) Draconis known as the Dragon’s eyes. Turn a telescope on 16 and 17 and the challenge takes a new twist – trying to split  17, a close pair of stars separated by 3 arc seconds and a single magnitude.  (Seventeen is north of 16.) That makes 17 very similar to nearby Mu (μ)  Draconis where the split is closer – 2.3 arc seconds – but there is no difference in magnitude. In fact, that makes this little area of sky near the Dragon’s head a real neat playground. You can start with the original Dragon’s Eyes because they’re easiest to find, then slide west about 4 degrees to Nu and west another 4.5 degrees to Mu. Real cool. Here’s a finder chart.

Click chart for larger version. Chart created from Stellarium screen shot.

I can split Mu with 10X50 binoculars, but it’s a real challenge for me to hold them steady enough. Much easier to  do if I mount them. However, 16 and 17 have a split that’s half again as wide while they’re nearly as bright and so they split more easily in binocular or finder.

I used an 80mm APO with a 6mm zoom to get a clean split of 17. All three stars are nearly the same color, though for me the secondary to 17 had a pale violet tinge. If you can split this close pair, try the same telescope and eyepiece on Mu. It would be interesting to see if you find it  easier – or more difficult to split than 17. On the one hand it should be more difficult because the stars of Mu are closer together. On the other, it should be easier because the Mu stars are the same magnitude whereas the 17 stars are separated by a magnitude.

What really strikes me about these stars, however, is the way that in such a small area of sky we have three pair of stars that qualify as “Dragon eyes” – that is, the stars in each pair are the same color and brightness – and a fourth pair – 17 – that almost qualifies, though there the secondary is dimmer. Hmmm . . . and which a stars are really the brightest? The honor goes to 16 and 17, since they are about 400 light years away – at least  four times farther than the Nu or Mu Draconis pairs!

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One Response

  1. I’m feeling a sense of ownership of this tiny region of sky now – I like that – a familiar territory to return to with several treats. I’m talking about the three dragon eyes, of course Tonight I returned first with 10X50 binoculars. I wanted to see if I could split Nu – and did barely,

    At first it only appeared elongated. But I got a pillow and lay down flat on my back on the deck and in that position witht he binoculars resting hard on my eyes I could hold them steady enough to easily split Mu. That sent me back for another try at the original Dragon eyes – Nu. And yes, I could split them. But again, it was a close thing, the problem being the difficulty in holding the glasses really steady.

    Still, i went in and got the much heavier 15X70 Celestrons, lay down, and tried again – very easy! Despite the extra weight. Both the extra light grasp and resolution of the 70mm objectives made all the difference. In fact I was so encouraged by this I went over to see if I could split Albireo – this makes an interesting progression with a split of about 90 seconds of arc for Mu, 60 seconds of arc for Nu, and close to 30 seconds for Albireo. But it split. And my wrists and arms were quickly tired.

    This is not the easiest thing for someone my age in my condition – hell, getting up and down off the deck isenough of a challenge 😉

    But I was fascinated with what I could see in the 15X70s and quite amazed at how much more light they gathered. These are not expensive binoculars. I got them for $45 used. What a bargain! Mounted, of course, they’ll do better – but they are just light enough so you can do this quick kind of hand held sweeping.

    So from Mu I went to Vega and the Double Double and then on down to Alibireo – oh, and I did stop and checked out that gorgeous red star, Delta 2 Lyra – that anchors the subtle cluster Steph 1 – and swung on down until I found M27 and Sagitta and, of course, the Coat Hanger. Just a delightful little summer excursion.

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