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A Pair of Jewels in the Crown: Σ1964 and Σ1965 (Zeta (ζ) Coronae Borealis)

It never ceases to amaze me what you can bump into with a telescope under a sky full of stars.  I was looking for something else entirely when I came across this pleasing pair of jewels, which is Corona Borealis’ contribution to the “double-double” category.

Actually, it was more a case of them finding me as opposed to me finding them.

And they’re not really in the crown — but they’re close.

The night started out with its customary dense cloud cover.  But — at 11PM I could see the moon attempting to bore its way through the clouds, and could just glimpse Arcturus as its reddish-orange glow peeked through a small hole.  At midnight the sky had improved to what you might call a three star night — Arcturus was now accompanied by Vega to the northeast and Saturn to the southwest.  And by 1AM I could see the clouds and haze were gradually lifting and the night looked like it might have some potential.

So after being deprived of my photonic fix for about a month  — not counting the quick hour I managed to steal a week earlier peering through clouds at Saturn — and ignoring my eyes that were attempting to settle in at half mast, I set up shop and decided I was staying put until the sun came up or the clouds came back — or until I fell asleep at the eyepiece.

Lost in the dark in search of Mu! What’s a Start Splitter to do? (Stellarium screen image with labels added, click on the chart for a larger view)

I stumbled on Zeta (ζ) Coronae Borealis at about 3AM when I was trying to get lined up on Mu (μ) Boötis.  Viewing at the top of the sky is not my first choice because it means sore knees (from kneeling on the deck to peer into the finder) and a sore neck (from being squeezed into a compact form about the size of an 80mm f/6 OTA).  So my aim was off by a few degrees when I gave in to my pleading knees and lined up the finder cross hairs on the brightest star I could see.

Then I leaned over to my right to look into the eyepiece — and centered in the center of the 18mm Radian (67x) I saw a bright pair of just barely separated white stars.

Having looked at Mu (μ) before, I knew I was off target  ……..  and I also knew I had no idea what it was that was looking back at me.

So I made a mental note of the location, moved over to Mu (μ), and spent some time absorbing the view — which is a triple, too!

Actually, it’s a bright primary with a pair of barely separated faint stars a short distance away — and it really is a splendid sight.

Then, still curious about whether I could retrieve that pair of white stars, I scrunched down on the deck behind the finder, found my target again, and peered into the 18mm Radian.  This time, they were up near the north edge of the eyepiece — and sitting down at the south edge was another pair of stars equally matched in magnitude, but a bit fainter and a bit further apart.

I could feel curiosity tugging at the bill of my Star Splitter hat, so I unfolded myself from my telescopic crouch, went into the house, opened the Cambridge Double Star Atlas to chart number ten —  and there they were, about three arc minutes to the east of Mu (μ)!

……. and there they were, about three arc minutes to the east of Mu (μ)! (Stellarium screen image with labels added – click on chart to enlarge the image, and click again for a larger image)

Then the bill of my hat directed me to the Haas book, which I opened to page sixty-one  ……  and she had both of them listed!

Σ 1964 (H IV 61)  (Data for AC pair)          Σ 1965 (Zeta {ζ} Coronae Borealis)  (H II 8)
HIP: 76563    SAO: 64821                            HIP: 76669    SAO: 64834
RA: 15h 38.2m   Dec: +36° 15′                   RA: 15h 39.4m   Dec: +36° 38′
Magnitudes: 8.1, 8.1                                     Magnitudes: 4.96, 5.91
Separation:  14.7″  (WDS 2012)                 Separation:  6.9″  (WDS 2012)
Position Angle:  86°                                      Position Angle:  306°
Distance: 286 Light Years                           Distance: 225 Light Years
Spectral Class: F5                                        Spectral Class: B7, B9

East and west are reversed in this refractor view. Click on the image to enlarge!

I was using a six inch f/8 Celestron refractor on this cool forty-five degree morning, and as the sketch at the right shows, both pairs of stars were easily seen in the same field with the 18mm Radian at 67x.  They’re farther apart (about half a degree) than that more famous double-double, Epsilon (ε) Lyrae, and they lack the charm of the ninety degree opposing alignments of Epsilon (ε), but that’s not to say they’re not a scintillating sight!  Σ 1964 hovers at one edge of the eyepiece, doing its best to imitate its much brighter pair of stellar companions gleaming from the opposite side of the field, with an attractive scattering of rather faint stars penetrating the dark sky in between.

Both of Zeta’s (ζ) bright stars appeared very white to me — no hint whatever of any other strange colors creeping in around the edges from out of the black of night.  Haas basically saw the same thing (“a very bright white and a modestly bright white”), Admiral Smyth saw “bluish white, smalt blue,” and Webb saw “flushed white, bluish green.”  Which just goes to show that getting agreement on star colors is like getting two Star Splitters to agree about which eyepieces are best.

But “smalt blue”????  Again, curiosity caught my cap, so I checked the Beford Catalogue and found that Admiral Smyth made his observation in August of 1831, leading me to wonder if “smalt” could be a word that had fallen out of useage.  I reached into my archives and pulled out an old Random House Dictionary printed in 1968 and found this entry for smalt: “powdered blue glass used to color vitreous materials.”  So now you know more than you did before ……..  😉  ………  or at least I do.

The other pair, Σ 1964, lurking down there at the south corner of my eyepiece, also appeared to me to be white, but more of a pale white in comparison to Zeta (ζ) because the two stars are fainter.  Haas describes them as gloss white, but the luster was lost to me.

What really intrigued me was determining which one was the primary.  With both of them appearing equal in magnitude, I guessed it was the eastern component, which would have meant that the other star of the pair had a position angle (PA) of about 270 degrees.  But when I looked at the data in Haas’s book, I found a PA of 85  — meaning it was the western one.  So armed with that knowledge, I went back and looked again — and I still couldn’t tell.  Maybe more magnification would have helped, but by this time it was almost 4AM, and the haze and clouds were creeping back in to reclaim the sky, and my eyes were flagging back down to half mast again.

BUT — what I didn’t know at the time, although if I had paid closer attention to the Haas book I would have noticed the “AC” under the star name — is that Σ 1964 is a triple, and that one of those components is a double as well.  Which means I have to pay a return trip as soon as the skies clear in order to see how many of these elusive points of light I can pull from the glare.  For the record, here is the entire observational data, fresh from the Washington Double Star Catalog:

Σ 1964   Magnitudes        Separation      Position Angle      Date of WDS Observation
AB:           8.07, 9.87                1.16″                     83°                                 2012
AC:           8.07, 8.06              14.70″                    86°                                 2012
AD:           8.07, 9.02              15.20″                    81°                                 2012
CD:          8.06, 9.02                 1.58″                    17°                                 2012

Given the typical non-cooperative seeing I usually get at my location, I suspect my chances of splitting AB and CD are about as likely as detecting an exo-planet with a 60mm refractor.  Looking at the magnitudes and the separation, it would seem that AD should be no problem.  BUT — look again!

AC, which is the one shown in the sketch, has a position angle of 85 degrees and AD is at 80 degrees.  And with AC having a spearation of 15.5″ and AD separated by 14.8″,  “C” and “D” can’t be very far apart.   In fact, the separation between the “C” of AC and the “D” of AD is actually the 1.6″ listed for CD  …….  so we’re back to hunting down exo-planets in the 60mm refractor  — rather unlikely, I think.   But, I’ll see what happens — with my trusty six inch f10 refractor and good seeing, it might be possible — and update this post if I have any luck.  Meanwhile, as always, if you have any luck with these faint photon producers, please post a comment and let us know!

During the time I spent absorbing the attractive view of this pair of doubles, I found myself intrigued by the Struve numbers assigned to these two stars — 1964 and 1965.  Thinking back to those years, I can still picture in my mind the Unitron ads on the back page of Sky and Telescope — and the warm summer afternoons or snowy winter days when I spent hours staring at the tantalizing photos of  those long white refractors perched on polished wooden tripods.  And more than likely, Questar had possession of the inside front cover.  And the price of a gallon of gas in 1964 and 1965 was  …….. well, let’s just say it was less than what you would spend now for a shrunken candy bar.

Stars — sometimes they really are time machines.

UPDATE!  May 24th, 3AM (2011)

If anyone had told me it was possible, I would have looked at them like they were trying to sell me a ten inch Clark refractor for a hundred dollars.  But in this case, I would have been wise to grab it!

Since discovering that Σ 1964 is a multiple star, I’ve been eager to get another look at it — although I had planned to do it with my six inch f/10 refractor.  But I suddenly found myself with a clear night that hadn’t been forecast, and not willing to bet that it was likely to last, or wouldn’t revert to rain, I set up my Meade AR-5 on an alt-az mount, which took all of about ten minutes.  At least if rain threatened, I could get it back in the house much quicker than the larger scope on its huge EQ mount.

So, after scanning the skies for several other objects, I pointed the scope up at Mu (μ) Boötis, made a sketch to add to the post on it, and then moved a few degrees to the east and found Zeta (ζ) Coronae Borealis again and it’s dimmer partner, Σ 1964, which I positioned at the center of a 10mm Radian (118x).

And it took about ten seconds to see what looked like a very small notch at the edge of the “C” component (meaning the CD pair), which is the one I thought I might have a slight chance at getting in a six inch scope — although I really wasn’t willing to bet the farm on it.  But I would have bet it couldn’t be done in a five inch scope.

So I was leaning more than a bit toward the idea that my eyes were being deceived by a spurious speck of something or other.   But to find out for sure, I grabbed a 14mm Radian and slipped it into a 2x Celestron Barlow, which produced a fearsome photon splitting 169x.  Not that I expected to see the darned “D” star even then.

Yet, there it was!  That little bud at the edge of “C” was now just barely separated from it, but it was clearly there, and during moments of good seeing, it was a faint speck of light surrounded by an ocean of black — although the beach was a bit thin on the side facing “C”.

Yet there it was …. but it’s a whole easier to see if you click on the sketch to enlarge it.

And after I had looked at it for about five minutes or so, I also realized that “A” was a bit extended in the direction of “C” — which matched up well with the eighty degree position angle of AB.  That one is a tight 1.4″ apart, versus the 1.6″ of CD.  I tried increasing the magnification, but the seeing wasn’t quite steady enough to pry the two stars apart — although it did stretch them a bit more.

I went back to the first sketch I posted for this pair and added an inset to the lower right hand corner, which as you can see here shows how close the split of CD was, as well as the stretching of the AB pair.

So  ……   the moral of the story is you never know until you try.  I’ve been surprised more than once lately at what I’ve managed to ferret from the darkness — either my eyes are getting better, or the Sky Gods finally decided to give me a break, or  ……  maybe I just better buy that Clark for a hundred dollars while my luck is leaning toward the unlikely.

(WDS data updated 5/30/2013)

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