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Draggin’ a Net through the Dragon (aka Draco), Part 1: 39 Draconis, h 2836, Σ 2377, Σ 2440, and Omicron (ο) Draconis

Draco is one of those long, winding, dim constellations that tends to escape attention, despite the fact that it’s spread over a large section of the northern sky.  But it has to compete for recognition with the more distinctive and much more famous configurations formed by both Ursa Minor and Ursa Major.  Which is a shame — it really deserves better because it boasts more double stars than you can shake a long focal length refractor at.

If you were facing northwest at about midnight at the end of September, you would see Draco in this position, winding through the sky between Lyra, Hercules, and Ursa Minor. (Stellarium screen image with labels added, click for a larger view)

One area of this dim constellation that does stand out, however, is the rectangular asterism formed by Beta (β), Gamma (γ), Xi (ξ), and Nu (ν) — the last one better known as the Dragon’s Eyes, a pair of stunningly white 4.9 magnitude stars separated by a little over a full minute of arc that will improve the view in just about any eyepiece/scope combination.  In late summer and early autumn skies, that four-sided asterism is easily seen in the west hovering near brilliant blue-white Vega.

Think of the line that runs northeast from Xi (ξ) Draconis to Delta (δ) Draconis as a highway, and the many double stars on its southeast side as roadside attractions begging you to pull off to enjoy a leisurely drive through more friendly surroundings. (Stellarium screen image with labels added, click for a close up of the side roads. 🙂 )

As I was looking at this area in my copy of the Cambridge Double Star Atlas one cloudy evening, I noticed that if you follow the northeasterly leaning line that stretches about eight or nine degrees from Xi (ξ), at the north corner of the rectangle, to Delta (δ) Draconis, you’ll find it’s paralleled by quite a cluster of double stars crying out for our attention.

And since I heard their cry — I didn’t feel their pain, though — I thought I might see if I could provide some comfort to them on a clear night.

So since it just happens to be clear tonight, let’s get take a look at five of them (we’ll save five more for later) — and if we’re fortunate, they’ll reward us for the effort.

We’ll start with 39 Draconis. To get there, start at Xi (ξ) Draconis. From there, you’ll need to move about three degrees to the northeast. You can use 7.4 magnitude HIP 88250 and 7.0 magnitude HIP 88654 as stepping stones, both of which can be seen in an 8×50 finder leaning a bit more to the northeast than what 39 Draconis does. Careful not to zip past it or you’ll skip off into interstellar space — in which case, you’re on your own. (Stellarium screen image with labels added, click on the chart for a larger view)

39 Draconis  (Σ 2323)  (H I 7 — AB only)        HIP: 90156    SAO: 30949
RA: 18h 23.9m   Dec: +58° 48′
*****   Magnitudes      Separation      Position Angle       WDS Data
AB:         5.1,   8.1                3.75″                  348°                     2012
AC:         5.1,   8.0              89.3″                     20°                      2009
AE:         5.1, 11.1            197.9″                     67°                      1910
AF:         5.1, 11.4               50.5″                     80°                      2008
Distance: 188 Light Years
Spectral Classifications: All A1
Status   A: spectroscopic binary   A&B: binary, orbit can be see here     A&C: binary    C: spectroscopic
(Source: WDS Sixth Catalog of Orbits of Visual Binary Stars)

My first attempt at this one was with my Meade AR-5 in poor seeing conditions — about a II on this chart — which meant this stunning star made a poor first impression.  I could pick out the easiest of the companions, eighth magnitude “C”, and 11.1 magnitude “E” was no problem hovering off in the distance.  But there wasn’t the first hint of “B” or “F.”

39 Draconis suddenly sprang to life . . . a “brilliant white star with a little smoke puff next to it split by only a small gap.” (East & west reversed to match the refractor view, click to enlarge)

The next night out, again with the AR-5, the seeing had improved to average —  or III  — which gave me my first glimpse of “B.”  And with that, 39 Draconis suddenly sprang to life, living up to Haas’s description of it as a “brilliant white star with a little smoke puff next to it split by only a small gap.”  I might be tempted to call it a beady little bluish-white star, instead of a smoke puff, but the overall impression is one of “profound contrast,” her words again.

But the best view came several nights later when the seeing improved to a very rare IV — which happens about half a dozen times a year here — as I was testing an eight inch Celestron SCT to see what I could see with an f/6.3 focal reducer attached to it.  And at 126x, I found “B” beaming back at me so confidently it was hard to believe I had never seen it on my first try.

“F” can be seen here barely outside the bright glow of the primary, while “B” is hidden behind it. (Photo rotated to match the sketch, click to enlarge)

What really prompted the use of the eight inches of aperture, though, was the search for 11.4 magnitude “F.”  Now all three of the nights I spent with 39 Draconis were interrupted by a very impolite and excessively bright full moon, spreading its intrusive light all over the sky as if it was trying to light up a mall parking lot.  Even in that bright sky, I had been able to find 11.1 magnitude “E,” but that was only because it was hovering off in the distance far enough to escape the combined glare of the “AB” combination.  I tried every trick I knew, from averted vision to high magnification, first in a multi-lensed 6mm Radian (210x), then in a minimally lensed 6mm Astro-Tech Plossl — heck, I even begged the moon to turn off it’s spotlight glow for a few minutes — and still “F” refused to come out from hiding.

It exists — as you can see in the above STScI photo — but even there, it’s well hidden.

As far as colors, I found the primary was a distinct yellow watered down by a weak touch of white, I could see a slight tinge of blue in “B,” and “C” was just weakly white.  Haas saw the “brilliant white” quoted above, while Admiral Smyth saw “pale white” in the primary, “light blue” in “B”, and described “C” as “ruddy.”  Not sure what that means, but I could be tempted to call the non-visible “F” muddy.

Our next star, h 2836, lies another three degrees northeast of 39 Draconis with another pair of stepping stones on the way, 6.4 magnitude HIP 90476 and 6.7 magnitude HIP 91397. (Stellarium screen image with labels added, click for a large view)

h 2836  (HJ 2836 in the WDS)           HIP: 91397    SAO: 17961
RA: 18h 38.4m    Dec: +60° 42.4′
*****   Magnitudes       Separation        Position Angle       WDS Data
AB:         6.7, 9.9                 33.1″                     316°                      2010
AC:         6.7, 9.9                 58.0″                    252°                      2010
AD:         6.7, 8.9               158.8″                    312°                      2010
Distance: 364 Light Years
Spectral Classifications: All F2

Now this one was another struggle under the mugging glow of that offensively bright moon — in fact, I really wasn’t convinced at first that I was looking at the correct star.  Again, my first view was with the AR-5 under poor seeing conditions, which only netted me the distant “D” on the first and second nights.  At over two arc minutes away shining at a reasonable magnitude of 8.9, I wasn’t exactly leaping up and down in the lunar light congratulating myself on a monumental achievement.  Far from it.  I was totally non-plussed by the view.  Neither an 8mm Radian (148x) nor a 6mm Radian (197x) brought “B” or “C” into view.    Way too many refracted moonbeams roaring through the air.  Ugh.  Very Ugh-ly.

. . . a view, the merits of which are concealed in subtleties . . . (East & west reversed, click for a larger view)

But I’ve become fond of John Herschel’s discoveries — which frequently lean toward the dim side, but often make up for that in some surprising fashion.  Knowing it wasn’t fair to forget this one, considering the obnoxious competition from the moon’s surplus of reflected photons, I gave it another chance.

So, again under a bright moon that made the short hop to it from 39 Draconis far more difficult than it actually is, I returned — this time with the eight inch Celestron.  And even with the additional aperture, it took some persistent staring to succeed, but gradually I could see “C” come out of hiding, and soon after the very bashful “B” poofed into sight.  And yes, it was worth the effort — once again, Sir John had uncovered a view, the merits of which are concealed in subtleties.  Now maybe under a dark sky — and I intend to give that a try — these stars will spring into sight with less effort, but as it stands now, I would have to say these require a large aperture approach only — probably six inches is the minimum.  But when armed with sufficient photon gathering apparatus, I find the tight little triangle formed by “B” and “C” with the blue-white primary to be very attractive, and “D” sort of adds an exclamation point to complete the configuration.  Once again, my Star Splitter hat is off to Sir John — there’s a reason the Queen appended that “Sir” to his name.

Update 9-28-2011:  I finally got a dark night to take a look at h 2836, and this time I gave it a try with the Meade AR-5.  The seeing was a horrendous and horrible I (and frequently diving to worse), but the transparency had its moments.  I caught one of those, and managed to just glimpse both “B” and “C” in a 12mm Radian (98x) and a 10mm Radian (118x) — averted vision did the trick.  But I never did catch either of them by looking directly at them.

Next we’ll make an almost ninety degree turn to the northwest and move about one and half degrees to reach Σ 2377. You can use 6.1 magnitude HIP 91606 and the slightly brighter 5.7 magnitude HIP 91315 to keep you headed on the right path. (Stellarium screen image with labels added, click to enlarge)

Σ 2377             HIP: 91396    SAO: 17963
RA: 18h 38.4m   Dec: 63° 32′
*****                   Magnitudes    Separation     Position Angle   WDS Data
AB:                         7.0, 9.8              16.7″                 338°                  2002
AC (WAL 150)      7.0, 9.7              95.2″                 350°                  2000
Distance: 620 Light Years
Stellar Classifications: K2 for all three
Status:  A & B optical (source: Haas)

A real triple gem with a straight line configuration. (East & west reversed, click for a larger view)

This is a REAL triple gem, easy to see with an 18mm Radian (66x) in the AR-5.  Haas didn’t see this one, but the observer (Geertsen) whose observation she records, described it as “a surprisingly easy pair, considering the data.  [It’s three stars in a straight line:] a pale yellow star, a white companion, and a close field star.”

The essence of this system lies in that straight line configuration — it grabbed my attention immediately.  And it really is surprising, considering the relatively dim magnitudes of “B” and “C”, just how easy they are to see.  In the AR-5, at least, there was no straining of the eyes, no reversion to averted vision — they simply were there at the center of the field.

My impressions of the color of the primary almost match Geertsen’s exactly — a pale white with a touch of gold.  The more distant “C” appeared as just plain old pale white, which may be the field star referred to in Geertsen’s observation, and all I can say about “B” is that it’s a dim point of light tucked up tightly against the primary.

Overall, really a pleasing sight.

OK, lets go back to h 2836 now. This puts us back on our well-worn northeast line once more, and a move another one and half degrees along it will take us right to our next goal, Σ 2440. (Stellarium screen image, labels added, click for a larger view)

Σ 2440         HIP: 93053    SAO: 18082
RA: 18h 57.3m   Dec: +62° 24′
Magnitudes   AB: 6.6, 9.6     AC: 6.6, 10.9     AD (WAL 98): 6.6, 12.8
Separation    AB: 17.5″         AC: 161.0″         AD: 53.8″
Position Angles   AB: 122° (WDS 2006)   AC: 60° (WDS 1999)   AD: 71° (WDS 1999)
Distance: 305 Light Years
Spectral Classification: G8 for all three

“D” is much more elusive and difficult than you might think, judging by this sketch — it took a 7.5mm Celestron Plössl (203x) in a six inch refractor to see it.  And then there’s that “UFO” between the secondary and the primary! (East & west reversed, click for a larger view)

This is not particularly an eye-catching trio of stars, but what it lacks in that department its surrounding field more than makes up for.  Over at the south edge is an almost straight, almost evenly spaced line of four closely spaced 11th and 12th magnitude stars, which are complemented on the north side by two wider spaced 11th magnitude stars and a tight pair of tenth magnitude stars.  The last pair look like good candidates for double stardom, but according to MegaStar, they’re not relatives.

The white primary of course dominates the scene, but I found 9.6 magnitude “B” easy enough to glimpse in a 20mm TV Plössl (45x) lodged in the diagonal of an f/15 60mm scope.  What really puzzled me though, and kept me busy for about twenty minutes trying to figure it out, was the ghost that kept popping up between the primary and “B”.  In the much brighter image of the 127mm Meade AR-5, I noticed that a star seemed to pop into existence in that location with averted vision.  It actually seemed to be brighter than “B”,  but when I tried to look directly at it, it disappeared and “B” regained its normal position.  Normally that kind of visual behavior indicates another star located closer to the primary, so I kept trying to dig it out, but never had any success.  It was very obvious at 84x in a 14mm Radian, but even the magical 7.5mm Celestron Plössl at 157x failed to solve the mystery.

I finally gave up and took a look at an STScI photo later, which showed nothing.  Maybe I discovered a virtual star popping into and out of existence — sub-atomic particles do it, so maybe stars do too!  Or maybe it was just a Draconian demon that had escaped from his lair in the Draconian Zone.

For now, I’ll just call it a UFO — Unidentified Fotonic Object.  😉

This is actually a four star system, but the “D” component escaped me entirely the first few times I looked for it.  At a magnitude of 12.8 and a distance of 53.8″, it was just in too close to the glow of the 6.6 magnitude primary to be able to dig it out.  I went back several nights later with my six inch f/10 and tried again, and was about to dub it the Unvisible  Fotonic Object when I suddenly thought I had a glimpse of it in a 12mm Radian (127x).  That called for confirmation, so I reached for the magical 7.5mm Celestron (203x) once more, and once more it came through.  It was a 50-50 proposition — half averted vision, half direct vision — but it popped in and out of view consistently enough that I was sure it was there.  Mission accomplished — finally!

A hard 120 degree turn to the south will take us to our last star, Omicron (ο) Draconis, which lies a short two degree hop away. You should be able to see it in your finder, forming a triangle with Σ 2440 and h 2836. (Stellarium screen image, labels added, click to enlarge).

Omicron (ο) Draconis  (Σ 2420)  (H IV 20)        HIP: 92512    SAO: 31218
RA: 18h 51.2m    Dec: +59° 23′
Magnitudes   AB: 4.8, 8.3      AC: 4.8, 11.5
Separation    AB: 37.0″          AC: 140.5″
Position Angle    AB: 318°  (WDS 2010)    AC: 324°  (WDS 1999)
Distance: 322 Light Years
Stellar Classifications: G7, G7
Status: A is a spectroscopic binary
(Source: WDS Sixth Catalog of Orbits of Visual Binary Stars)

This one caught me by surprise.  To start with, I didn’t even have it on my list because it’s ignored in the Cambridge Double Star Atlas.  Although it’s labeled as a double, there’s no data on it at the back of the atlas, and the Σ 2420 identification is missing from the chart.  I dug up a reference to it, found the correct Struve number for it, looked it up in the WDS, and decided to go back and see if it was worth a glance.

A “showcase pair” that deserves a whole lot more than a mere glance . . . (East & west reversed once again, click … to … enlarge)

It was, and it deserves a whole lot more than a mere glance.

The primary possesses that Draco gold I’ve seen so many times in this constellation recently, and the secondary packs a very pleasing shade of turquoise.

Even though it’s overlooked in the Cambridge Double Star Atlas, it isn’t by Haas.  She describes it as a:

Showcase pair.  60mm, 25x: A bright star with a wide little companion in the pretty combination of yellowish peach and clear gray.  Webb: ‘Very yellow, ash.’ “

Admiral Smyth has it as “orange yellow” and “lilac,” and Sirs James South and John Herschel, who list it as Sh 284 in their joint catalog of 1824, described it as “strongly red” and “blue.”

So the consensus of opinion is blue for “B” and gold-peach-orange-yellow for “A” (certainly a happy combination of colors), with Herschel and South’s “strongly red” thrown in to keep things interesting.

We’ve got another five Draco gems hovering just a bit further along our northeast sloping line that we’ll tackle next.  Right now, I’m encountering what might be politely called a rain delay — I have other words for it — which can’t last forever (I’m being optimistic now) . . . . . . although my neighbor down the street seems to be hard at work building an ark.

So — hopefully we’ll return and continue dragging this net through the Dragon in search of more of the delectable Draco gold.

Clear Skies!  (and if you have a surplus, send them to the north Oregon coast — I’ll pay the shipping!)

P. S. — and we did return, too!  Here’s Part II!

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