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Izar (Epsilon [ε] Boötis)

Izar  (Epsilon [ε] Boötis)    (Σ 1877)  (AB is H I 1)        HIP: 72105    SAO: 83500
RA: 14h 45.0m    Dec: +27° 04′
Magnitudes        AB: 2.6, 4.8                           AC: 2.6, 12.0
Separation         AB: 3.0″                                  AC: 175.5″
Position Angle:  AB: 345°  (WDS 2011)        AC: 255°  (WDS 2001)
Distance:  210 Light Years
Spectral Type: K0

Stellarium screen shot with labels added (click on image for a larger view, and then click a second time to enlarge once more).

Located to the northeast of Arcturus, Izar is the first of the stars that forms the east side of the kite-shaped asterism of Boötes — and it can be a very frustrating little devil to split.  On a rare night of stable seeing it can easily be done in a 60mm scope with good optics.  But on a night of poor seeing (more common it seems), you’ll find it hopeless in an eleven inch SCT.   But regardless of what you finally pry it apart with, you’ll find the time has been well spent.  The reward comes in the form of a very small secondary nestled right up against a much larger, colorful primary.

A pale white secondary seen here nestled up closely to an orangish primary, while “C” looks on from a distance. East and west reversed in this image to match the refractor view. For the full effect, turn off the lights and click on the image!

If you attempt it with a small scope of between sixty and eighty millimeters,  you’ll find the very small companion is often hiding in the diffraction ring.   In that case, I’ve found that varying the magnification will usually bring it out.  In Double Stars for Small Telescopes, Sissy Haas describes the primary as amber-yellow and the secondary as deep blue.  She credits Admiral William Henry Smyth with “pale orange; sea green,” which pretty well describes the colors I see, although I lean more toward gold than green in the secondary — but I can clearly see the green tint most of the time.

Now if you’ve never looked at Izar, you’re very likely to discover that once you’ve split it, it’s siren call will keep luring you back for another view.   I’ve lost track of both the number of times I’ve pointed a scope at it, as well as the amount of time I’ve lingered over it admiring the view  ………………………..

and wondering if any Izar-ians were looking back at me.  😯

Updated Observation

Since Boötes is a spring and summer constellation, most of your observations of it are likely to be in reasonably warm and comfortable weather, as was the case with the one described above on a sixty degree evening in April of 2010.  But if you’re an adventurous type, and like to observe in the early hours of the morning, you can catch it in the brisk winter air.  Which, in defiance of good sense, is what I did on the following occasion.

Here’s the scene:

It’s 2AM on the morning of February 19th (2011), the sky is clear and, thanks to a barely waning moon that is about 97% full, it’s also bright. It’s 35 degrees and there’s a cold — very cold — wind blowing at me from the northeast. And the stars in the sky that I can see are twinkling like they’re all about to explode.

But I can’t resist. The lure of those twinkling white dots of light up there in that pale blue sky is not meant to be missed.

My deck is out of the question because it’s got a thin coat of ice on it — not the place for a star-splitter who is focused on splitting stars instead of paying attention to his footing.

So out into the drive I go with my 63mm Zeiss — facing almost directly into that chilling north wind that is determined to freeze me in place in my chair.

But good sense will only get me a warm bed with an absence of starlight.

My view of the sky is limited from here, so I spend some time on Algieba — quite a lot of time, actually — then look at Saturn for a bit, and finally turn the Zeiss to face the Izarian music.

The seeing has improved a bit by now, which I was hoping for — but not much. When I came outside, it was so bad even Izar was twinkling.

So, the question confronting the lens at the end of the 63mm f 13.3 Zeiss is:  Can you split this one in these confounded conditions?

We — which is me and Herr Zeiss — start with an 18mm Tak (47x), not with the intention of carving out a split, but just to survey the surrounding stellar neighborhood. Not bad, things looks reasonably stable.

Next move: a 15mm TV Plössl (56x), which just did a great job on Saturn and was breath-taking on Algieba. Not quite a split now, but it’s close.

So Herr Zeiss and I confer and decide to make a forward leap of faith into the middle of a 12.5mm Tak (67x). Now that may not seem like a lot of magnification, but in this seeing, it’s about the limit of what will work.

In it goes, and after several attempts to catch a sharp focus while the image is bouncing around, the devious little dot of a secondary pops into view — and out of view — and into view — etc, etc, etc.

But — we got it! Herr Zeiss und Herr Nanson.

We stayed with it for about fifteen minutes, which was all I could take. At times the image was nice and sharp, at other times it would suddenly balloon up as if someone was holding a match beneath it, and most of that time it was bouncing around so much it made me think I was being tossed around the deck of a small boat on a storm ravaged sea. So enough was enough.

And anyway, my fingers were now ice, and my toes were edging toward the negative side of the Centigrade scale — but Herr Zeiss didn’t seem the least bit perturbed.

I think he was hypnotized by the strange stellar tones of that Izarian Musik. Fortunately it wasn’t penetrating my numbed mind.

So, we called it ein gutes Nacht and headed for the Haus, accompanied by our four-legged companion, Herr Klaus.


3 Responses

  1. On May 31, 2009 I had just acquired used a 3-6mm Televue Zoom and used Izar to test it. Here’s my account from that experiment.

    I used the zoom on both the TeleVue 60mm and the 120mm Skywatcher APO and my test objects were the Moon and the close double, Izar in Bootes. It did fine on both. I could just split Izar cleanly with the 60mm and the zoom cranked all the way up to 120X ( 3mm) . It split a tad better with the 2.5 Nagler – but mainly the 2.5mm Nagler gave me more time on target – and since I’m strictly manual these days the extra field of view of the fixed focal length Naglers is important. Same with the Moon.

    What was surprising was that the Moon could not take the 3mm setting on the 120mm scope – but then, that was 300X. It’s unusual for my skies to support that much power and my Clear Sky Clock had predicted poor seeing and there was 50-80 per cent clouds drifting through. But the seeing was a lot better than I expected because the real surprise was that Izar accepted the 3mm – 300X . I got a perfect split with it – nice round stars with two or three diffraction rings – it did go in and out with the seeing some, but not as much as the Moon at that power. Again, I preferred the view of Izar with the 3.5mm Nagler because of the wider fov giving me more time. But I didn’t see anything to choose from in terms of the quality of the split, contrast, and the split being good to the edge of the field.

  2. Interesting. Reading my previous comment is a reminder that I have to bring this telescope routlette to a close. Two things stand out. I was using a 60mm TV then. I sold it. I just bought naother one. In it’s inthe mail. I also explain the advantage of the 2.5 Nagler over the zoom – and tonight I could have used that 2.5 Nagler. But, of course, i sold it.

    Now what was different about tonight was the ETX90 I was using. That’s a scope I’m gaining serious respect for. I say tonight – I mean this morning. And it was 21°F and I had neglected to bring handwarmers to the observatory and my fingers were in pain.

    I had beens witching between a C8 and the ETX90, but by the time I got to Izar I wasn’t willing to play with switching scopes – too cold and the skies were too unsteady for the larger scope.

    I just used the ETX90 and with the 7mm Nagler, an eyepiece it favors, and I saw a beautiful single star with clean diffraction rings. Must be the wrong star, I thought. But a check of the red dot finder showed I was on Izar, so I trotted out the 5mm Nagler.


    Nice blue companion right where it should be – but in the second diffraction ring. Or maybe half in, half our. In any event, a clean split with black sky. Score one more for the ETX90. Boy – really can’t wait for the ETX125!

    Now let’s see – ETX90 at 5mm – 250X. And 60mmTV at 2.5mm -144X! Uh oh – ETX 90 at 7mm (178X) couldn’t show me a companion. Interesting. Of course, conditions were probably different, but it suggests to me that the ETX90 is throwing more light into the diffraction rings making a close split like this more difficult. well, it will be fun to do a side-by-side.

  3. 1 AM, June 21st (2011)

    First day of summer! Hah! Fifty-two degrees and fog hanging just over the horizon. This has been such a cool June that I’m beginning to think the calendar is stuck on March.

    But that has nothing to do with the sweet tones of Izarian Musik I can hear floating from Boötes and wafting through the damp morning air. My companions this morning are a Meade five inch refractor (AR-5, f9.3) and a Lafayette 60mm f13.3 (sitting on top of it) that has been revived with a Carton lens. And of course, Herr Klaus, who has given up and gone in the Haus to escape the dampness. Smart dog.

    In the AR-5, I can’t see the first sign of a bud on Izar at 66x — but since this has been a late spring, no surprise there.

    At 118x, though, it looks like summer has arrived after all — that miniscule 4.9 magnitude companion has sprouted from the northwest corner of the primary and is sitting there very calmly looking back at me, whistling in strange Izarian harmony with it’s parent. Or maybe those Musikal tones are coming from a car that just went down the street.

    Not one to leave the Lafayette in the lurch, I peer through a 20mm Astro-Tech Plössl (40x) and can see an attractive glowing orange ball of fire, but of course, no secondary at that weak magnification. In goes a 9mm Meade Plössl (89x), and still no luck. But as is usually the case with the Izarian secondary in a 60mm scope, I have a hunch it’s hiding in the first diffraction ring.

    Next into the diagonal is the ever-effective Celestron 7.5mm Powerful Plössl (107x), which rarely fails. Hmmm — not sure. I think I can see the secondary popping free of that diffraction ring every now and then, but it won’t stay put long enough to get a firm fix on it.

    So now, since it looks like more Plössl power is needed, I swap an Astro-Tech 6mm (133x) version into the diagonal, bend down to the black barrel, sneak up on the lens silently …….. and take a peek.

    It’s THERE! No it’s not. YES! Wait, it’s gone now. THERE! Well, it was. It’s BACK!. Gone. Again. Geez. This could go on all night.

    But as I sit there and watch that secondarial dance, I realize it’s rhythmic. Certainly not a rhythm known to an earthling, but none the less, there’s a definite pattern to it.

    Izarian visual Musik for sure!

    Hmmm, I have a hunch I better sneak back into the Haus with Herr Klaus and dry out my Star Splitter hat and find some nourishment for my neurons. I think all this dampness is causing them to short out. 🙄

    Clear Skies!

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