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Under the Left Horn of the Bull: Σ730 and h 3275; Σ674 and Σ680; Σ740 and Σ742

Taurus is seen here hovering over Orion. Click once on the image (and any of the others that follow) to enlarge it. Note that the “left” horn of the bull is in reality the horn on the east side of Taurus. (Stellarium screen image with labels added)

It’s surprising sometimes how close constellations are to one another.  For instance, I don’t habitually think of Orion and Taurus as bordering each other, although I know full well they do.  They just seem like they should be farther apart.  In reality, the top of Orion’s shield (which really looks much more like a bow to me) almost reaches to Aldebaran, and the distance from Meissa (Lambda Orionis) to the Crab Nebula (M1) is barely over ten degrees.  So I was surprised — once more — when I discovered the first of our pair of doubles is only six degrees north of Meissa.

So strap yourself in to your observing chair because we’re going for a ride on the Bull — but since all three of the pairs we’re going to look at lie within a relatively small area of sky measuring four degrees by four degrees, we’ll keep it short!

h 3275               HIP: 25745    SAO: 94589
RA: 5h 29.8m   Dec: 18° 25′
Magnitudes: 7.7, 8.2
Separation: 56.3″
Position Angle: 21°  (WDS 2002)
Distance: 653.6 Light Years
Spectral Classification: A0

Σ 730  (H N 124)          HIP: 25950    SAO: 94630
RA: 5h 32.2m   Dec: +17° 03′
Magnitudes: 6.0, 6.4
Separation:  9.4″
Position Angle: 142°  (WDS 2007)
Distance: 1117 Light Years
Spectral Classification: B7

Using the chart above, we’ll start our trip at Meissa.  You’ll find it located at the top of Orion just north of a line drawn between bright reddish-orange Betelgeuse and blue-white Bellatrix.   Move north eight degrees from Meissa and — if you have relatively dark skies — you should see the faint reddish-orange glow of 119 Tauri without optical aid — or you can use a pair of binoculars, in which case you won’t be able to miss it.  But if that doesn’t work well for you, draw a line from Meissa to Zeta (ζ) Tauri, then backtrack about two degrees and you should see 119 Tauri just to the west of that line.  In a finder with a four to five degree field of view,  you should easily be able to see Zeta (ζ) and 119 in the same field.

Σ 730 and h 3275, and the surrounding area. (Stellarium screen image with labels added)

119 Tauri is a very interesting star all by itself, a class M2 giant much like Betelgeuse, located about 1900 light years from us.  Once you have the beautiful gleam of this reddish-orange star centered in your eyepiece, you’ll see h 3275 about half a degree to the southwest.  It’s a widely spaced pair of stars that is very obvious in a small scope.  I was using a pair of scopes side by side — an old 80mm Mizar equipped with an f/15 Carton lens and a Tasco 60mm f/16.7.  A 25mm Plössl (48x) in the first scope and a 20mm Plössl (50x) in the second one provided similar views.  Both components are basically white in color, although at magnitudes of 7.7 and 8.2, the color is not particularly striking.  The “h,” by the way, is a reference to John Herschel, who is credited with the discovery of this one.

A move of 1.5 degrees south will bring you to Σ 730.  Considerably brighter, and much more closely spaced, it provides a wonderful contrast to h 3275.  With a 30mm Tak LE (33x) in the 60mm scope, I could just barely fit h 3275 and Σ 730 in the same field of view.  In the eyepieces I mentioned above, though, I found Σ 730 really stands out well when centered because it’s the brightest pair of stars in the field.  This one deserves Haas‘s description as a “showcase pair” in a 60mm scope, and I think her “blue-white and yellow-white” pretty well covers it also.

Of the two pairs, Σ 730 is certainly the most appealing.  But in addition to the contrasts in brightness and spacing, what really caught my attention was the contrast in position angles.  Σ 730 lines up in a south-easterly direction, and h 3275 aligns to the northeast, which adds to their appeal when seen in the same field.  Also particularly eye-catching is the arc to their west which is formed by 117, 113, 110, 111, and 115 Tauri.  These look best in the finder, or even better, a pair of binoculars.  No name has been given to this arcing asterism, so I’ll call it the Bull Cluster, or BC for short!

Σ 674          HIP: 24663    SAO: 77084
RA: 5h 17.5m   Dec: +20° 08′
Magnitudes: 6.8, 9.7
Separation: 9.9″
Position Angle: 149°  (WDS 2009)
Distance: 239 Light Years
Spectral Classification: F7, F5

Σ 680           HIP: 24820    SAO: 77098
RA: 5h 19.2m   Dec: +20° 08′
Magnitudes: 6.2, 9.7
Separation:  9.5″
Position Angle: 206°  (WDS 2011)
Distance: 431.4 Light Years
Spectral Classification:  K0

Σ 680 is the brightest of these two pairs, so “theoretically” it should be the easiest to find.  There are two ways to get to it.  First, if you’re starting from the  h 3275/119 Tauri area, move three degrees to the northwest.  Or, if that proves difficult, start from Zeta (ζ) Tauri, the star that marks the top of the bull’s left horn and move northwest past 114 Tauri to 109 Tauri, a total of four degrees — both of these last two stars can be picked out of a dark sky without optical aid.  From 109 Tauri, move south two degrees, and you’ll come to the distinctive parallelogram formed by Σ 680 and Σ 674 and the two stars to their south.

Σ 680 and Σ 674 are seen here in the middle of this image, and our next pair of stars, Σ 740 and Σ 742, are at the upper left. (Stellarium screen image with labels added)

As my subtle hint above should indicate, though, these two are a bit elusive.  The first night I searched for them, I was using the 60mm and 80mm scopes described above in the  h 3275/Σ 730 discussion.  I had a heck of time locating these two stars because I couldn’t detect the faint components of either one.  I searched, and searched, and searched  ……………  and kept ending up at the same place — but without any sign of a split.  I tried several times from both the 119 Tauri area and the 109 Tauri area.  In fact as I discovered later, I could even pick out Σ 680 visually with averted vision.  But without a split to confirm I was looking at the correct stars, I just couldn’t be sure I was where I wanted to be.  As my old Uncle Harry used to say, “Son, if it ain’t workin’, don’t keep doin’ it harder.”

And it wasn’t.  So I didn’t.

I went on to other things muttering about stellar stuff quietly enough not to disturb the neighbors.

Reproduction of sketch of Σ 680 and Σ 674 – the black arrow at the upper left points to west in this image to match the eyepiece view.

HOWEVER —– I don’t give up easily.  The next night I was back — and this time with a larger Star-Splitter, the Meade AR-5.  I don’t remember what I paid for this gem, but for a light grab-it-and-throw-it-on-the-mount scope, it’s been a heck of a bargain.  So, to get to the point, I was looking in the right place the previous night, but I just didn’t have enough aperture.  When I pointed the AR-5 at Σ 680, there was the faint companion, clear as could be, and over on the left side of the field about thirty arc minutes away, Σ 674 was even more obvious.  And what a delight! — two primaries of almost the same brightness accompanied by two pinpoints of light that were about equally faint.

As for colors, the 6.2 magnitude primary of Σ 680 had a slight, but obvious, orange tint in the AR-5 at 74x;  the 6.8 magnitude primary of Σ 674 was white with a tinge of blue to it.  Of the two pairs, the secondary in Σ 680 was more difficult to see because of the larger difference in magnitudes and also because it’s almost eight tenths of an arc second closer.  And working at these faint magnitudes, that’s just enough to be significant.

I also had my 63mm Zeiss out that night, so now that I knew I had the field correctly identified, I pointed it in the correct direction, lined up what by now was a very familiar field in the finder —- und Heilige Sternen im Himmel! —- was able to split both stars with a 15mm TV Plössl (56x)!   The Σ 680 secondary gave me a bit of trouble, but I did manage to hold it with direct vision for several seconds at a time.  I really don’t think I would have ever seen those two faint specks of light without first having seen them in the AR-5.  Knowing EXACTLY where to look, and just as important, HOW to look, makes a huge difference in a person’s ability to see faint objects such as these.  And Herr Zeiss deserves a bit of credit, too – Vielen Dank, mein Herr!

Σ 742  (H I 70)               HIP: 26328    SAO: 77313
RA: 5h 36.4m   Dec: +21° 59′
Magnitudes: 7.1, 7.5
Separation:  4.1″
Postion Angle: 275°  (WDS 2012)
Distance: 212.5 Light Years
Spectral Classification: F8
Status:  Physical, orbital chart and data can be seen here.

Σ 740                             HIP: Not assigned in Simbad    SAO: 77308
RA: 5h 36.4m   Dec: +21° 11′
Magnitudes: 9.0, 9.9
Separation:  21.7″
Postion Angle: 121°  (WDS 2004)
Distance:  ?????
Spectral Classification: B2

A quick glance at the upper left hand corner of the above chart for Σ 674 and Σ 680 will show you the location of our next two stars, Σ 740 and Σ 742.  Both of these lie very close to bluish-white Zeta (ζ) Tauri, a B class giant of a star located 420 light years from us.  A look at the more detailed chart below (a mirror image view which matches that seen in a refractor equipped with a diagonal) shows Σ 740 lying immediately west of Zeta (ζ) Tauri.  In fact, anyone who has spent much time looking at the Crab Nebula (M1) will find that both of these double stars are a familiar sight.  Haas’s description is very accurate: “A close pair of bright stars, and a wide pair of dim stars.”

Mirror image (west and east reversed) to match the view as seen in a refractor using a diagonal. (Stellarium screen image with labels added)

Σ 740 is certainly not an attention grabber, and determining color is out of the question because of the faint magnitudes of the components.  Faint — but well within the reach of a 60mm refractor because of their relatively wide separation.  I could split it easily in the Tasco 60mm f/16.7 with a 25mm Plössl (40x).

If you’re using an eyepiece with a field of view of about 1.3 degrees, you can see Σ 742 at the north edge of your eyepiece if you position Σ 740 at the opposite, southern, edge.  In fact if you look closely at the coordinates above, you’ll find both of these pairs of stars have the same right ascension, so all you really need to do is just slide up that imaginary line in the sky to get there!

On the other hand, if the field of view of your eyepiece is too narrow to see both pairs at the same time, center the line of four stars which lie on the opposite side of Σ 740 from Zeta (ζ) Tauri, draw a line northeast from the southernmost of the four (it’s labeled with a magnitude of 8.2) to the northernmost one (labeled 7.6), and continuing in that direction, nudge your telescope just a bit until Σ 742 comes into view, probably with the Crab Nebula at the west edge of your eyepiece.

With a separation of 4.1″, this is the closest of any of the doubles we’ve looked at here.  In the 60mm f/16.7, it was clearly elongated with a 30mm Tak LE (33x) — almost split, but not quite.  I had to move up to a 20mm Plössl (50x) to get a clean split, but when I did, it was a beauty to look at — two barely separated points of light of almost identical brightness.  While each of the components were white in the 60mm and the 80mm scopes, I thought a detected a slight tinge of very faint red in the primary on the next night when I looked at it with the Meade AR-5 at 59x.  The best view I had in all three scopes was in the AR-5 with a 16mm Meade SWA (74x) —– ravishing, riveting, rousing even!

And through it all, the Crab Nebula hovered at the west edge of the field like a ghostly presence.  Here’s a sketch from Jeremy Perez’s web site, which is far more likely to resemble what you see in the eyepiece of your telescope than a photograph will.  But we can’t pass pass up a chance to see a good photo of the Crab either, so here’s an image of it captured by the Hubble Space Telescope.

These observations were made on the dark frigid nights of Jan 2nd and Jan 3rd, 2011.  Information about 119 Tauri can be found here, and for Zeta Tauri, look here, both of which are pages from James Kaler’s web site.

And the German means “Holy Stars in the Sky!”  — but it has a certain tone in German that it loses in translation.

And speaking of the sky, I hope yours are clearer than mine!  😎

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