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On the Fringes of the Throne: Iota (ι) and Psi (ψ) Cassiopeiae

At the northeastern tip of Cassiopeia are two challenging multiple star systems that will quickly draw any dedicated Star Splitter who likes his or her stars closely separated and suffused with subtle color.

Greg mentioned both of them to me a month or so ago, which rattled loose a dim and distant memory of having spent some time on them several years ago.   And when I looked up their statistics in the Washington Double Star Catalog, I immediately felt the call and the draw of their regal beauty — after all, this is the domain of Queen Cassiopeia.

A quick look at the map below will show  where we are:

Iota (ι) lies at the northeastern tip of Cassiopeia, and Psi (ψ) can be found northwest of Epsilon (ε). The three of them form a neat little equilateral triangle. (Screen image from Stellarium with labels added – click on the map for a full size view).

Iota (ι)  Cassiopeiae  (Σ 262)  (AB is H I 34)  (AC is H II 4)
HIP: 11569    SAO: 12298
RA: 02h 29.1m   Dec: +67° 24′
Magnitudes         AB: 4.6, 6.9    AC: 4.6, 9.0   AD: 4.6, 8.5
Separation          AB: 2.6″           AC: 7.1″         AD: 210.9″
Position Angle   AB: 229° (WDS 2012)   AC: 116° (WDS 2010)  AD: 60°  (WDS 1999)
Distance: 141.6 Light Years
Spectral Classification   A:  A5    B:  F5    C:  K1
Status:  AB is physical, an orbital chart and data can be seen here.

These stars are really a delight to look at in apertures of 60, 80, and 105 millimeters. As Iota (ι) comes into view, you’re greeted with a very tight knot of three stars.  A casual glance would fail to catch the tight “B” component, and very likely would miss “C” also because of the 4.4 magnitudes of difference between it and the primary.  Unlike some of the wider triples and doubles discussed in other posts, the tight distances between the three stars requires close scrutiny — as Mr. Spock might say, “Captain, this observation will require a performative act of cognition.”  And hanging out there in distance, all alone, is frequently ignored 8.5 magnitude “D.”

“B” and “C” hover around the primary at the center of this sketch as “D” drifts out in interstellar space all by itself. (East and west reversed to match the refractor view, click for a version without this caption)

And the close scrutiny required to pick out “B” and “C” is where the charm of this system lies.  I found my vision was drawn directly to the 4.6 magnitude yellow primary and only gradually did the other two stars begin to reveal themselves.  In my six inch refractor, though, all three stars leap out from the background of the black sky, and the beauty of the view in that instrument is the rich colors of the primary and secondary.

And there’s more than meets the sharp observing eye here.  “A” has a very close companion, designated as “a,” as does “C.”  For a view of the closest five  stars in this complex system, take a look at this photo taken at Lick Observatory using adaptive optics.

Below are notes from three recent observations:

August 23rd, 2010

I was using a pair of 80mm f/12 refractors on this night, mounted side by side.  For a photo of that set up, take a look HERE.

Using a 20mm Plössl (60x), I had to look very closely to see all three stars.  The view was much cleaner with a 15mm Plössl (80x), and a bit better with an 11mm Plössl (109x).  Still, it was very tight at each of those magnifications, and bright moonlight made it especially difficult to see the ninth magnitude “C” component clearly.

August 25th, 2010

Six inch f/10 with a 60mm f/15 mounted on it, and a black screen in the background to block stray light. (Click on image for a larger view).

This time, I pulled out the big gun,  a six inch f/10 refractor, and the view was so sublime I sat glued to my chair for a good thirty minutes.  The “B” component was right up against the primary with a 14mm Radian (109x).  Increasing the magnification to 138x with an 11mm Plössl yielded a fantastic view, as did a 9mm Ortho (169x).  The primary is a rich yellow, the very close “B” component is white, and “C” was really too faint to show much color, but I could call it gray without too much problem.  Haas describes the first two as lemon yellow and blue, and leaves the fainter “C” as a speck.

In the 60mm f/5, I couldn’t detect “B” with an 11mm Plössl (82x) because the diffraction ring hid it.  “C” was barely visible.  I increased the magnification to 129x with a 7mm Ortho and was able to detect “B,” but at that point “C” became difficult because of the glare from  “A” and “B”.  Bright moonlight was a factor again during this session.

September 3rd, 2010

Tonight I thought I would take another look at this beautiful triple with a 105mm f/15 refractor, and with a 60mm f/16.7 refractor which is mounted on it. At the time I was looking at Iota (ι), the seeing was erratic — sometimes pretty decent, and at other times, downright horrible.  However, unlike the previous two nights, there was no bright moon in the sky.

In the 105mm refractor, all three stars were very obvious in an 18mm Radian (83x).  The “B” component was very close to the primary, but when the seeing settled down, it was a beautiful little pinpoint of light.  The view in the 60mm scope was very similar with a 15mm Plössl (67x).   This time, using the 11mm Plössl (91x), the tight “B” component was visible outside of the diffraction ring, and as before, “C” became lost in the glare of the additional magnification.

And now, if you’ll excuse the poor pun, we’ll take a deep breath, let out a sigh (ψ), and move on to ψ (Psi) Cassiopeiae, which is a short hop away to the northwest.  Actually, there was more than one reason to let out a sigh at this point.  As I was moving the scope over to Psi (ψ), what sounded like half a dozen coyotes starting howling off to the north of where I was observing.  I’ve heard an occasional howl from them before, but this was a chorus.  I don’t know who they were singing to, but my four legged observing companion, Klaus, had both ears pointed up as far as they would go.

Psi (ψ) Cassiopeiae               HIP: 6692    SAO: 11751
RA: 01h 25.9m   Dec: +68° 08′
*****                  Magnitudes    Separation    Position Angle    WDS Data
AB: (Bu 1101)    4.7, 14.0               2.4″                   38°                 1970
AC: (H V 83)       4.7,   9.2             20.3″                  128°                2007
AD: (Bu 1101)   4.7,  10.0            19.1″                  131°                2006
CD: (Σ 117)       9.2,  10.0              2.3″                  250°                 2009
Distance: 193 Light Years
Spectral Class: K0
Status:  AC is optical; CD is physical; C & D are optical companions of A

This is a complicated star system, to put it mildly.  The primary, an orange giant, has a fourteenth magnitude companion (“B”)  three arc seconds away — needless to say, I didn’t try for that one.  The “C” of the “AC” combination is also a double,  consisting of 9.2 magnitude “C” and tenth magnitude “D,” a close 2.3″ away.  And if that wasn’t enough, it carries three different designations, as shown in the parentheses in the data line above.  If that confuses you, don’t despair — I’m confused, too,  and I just described them.

Psi (ψ) is seen here through the lens of an 8mm Radian magnifying the photons passed on to it from the Jaeger’s doublet of a six inch f/10 refractor. The primary was a very rich gold color, and I could see very slight hints of blue in both of the fainter companions. (East & west reversed, click on the sketch to see a version minus this caption)

What you’ll see on close examination is a bright primary with two faint and barely separated companions — that is if you’re using enough aperture.   On the same night as the previous observation above, September 3rd, the split between the primary and the two companions nineteen and twenty arc seconds away was easy with an 18mm Radian (83x) in the 105mm scope.  However, trying to separate those two tenth magnitude companions 2.3″ apart was an exercise in futility.  I tried a 14mm Radian (107x), a 12mm Radian (125x), a 10mm Radian (150x), a 9mm Plössl (167x), and 7mm Ortho (214x), but never could really be sure I had both of them in view.  Use of averted vision was a must.  The best I can say is that one would suspect a double here because they never would quite come into focus as a single star.

In the 60/1000, averted vision was required to pull the the pale dot that was the faint pair out of the glare of the primary in a 15mm Plössl (67x).  Using an 11mm Plössl (82x), I could see them with direct vision a bit easier, but averted vision worked much better.  There was no hope of splitting the “two of a kind” in that scope, however.

So the question remains:  Will one of the two Star Splitters of this series of tremendously interesting double star adventures be able to split the two tenth magnitude companions with more aperture?   Will Greg be first?  Will John be second?  And who’s on third?  Will Klaus sing out to the chorusing coyotes when one of us succeeds?  Stay tune — we ain’t finished just yet!

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6 Responses

  1. My bet is you’ll bag Psi with the 6-inch – nothing less – and probably before the AR-6 arrives here and I have a chance to try for it ;-).

    Now Iota is another thing. I just got in from an early morning session in which that was a highlight and for the first time I felt I detected color in all three stars. I was using the Ar-5 127mm F9.3 and with a 5mm Tak LE I had a mesmerizing split. The fainter C component seemed to me to show a green tint, while the brighter, but closer, B star was a pale green.

    It’s interesting – with this system the fainter C star I always find much easier and it showed the strongest color to me. That 7 second separation means more, despite the greater magnitude difference. But in the 127 this morning – transparency was exceptional and seeing above average – there was no problem. All three stars popped into view together as soon as I focused properly, (The Tak, btw, did better on this system than the the Nagler 5mm and the Nagler 6-3 zoom. )

    Oh – I should mention that 236X was the limit. I couldn’t go higher with the zoom without losing quality.

    So you have coyotes too! Man, they do send shivers down my spine when they get barking together. The first night I heard that I walked out to the road expecting to find that some poor animal had been hit by a car. But when I got there I could tell the sound was coming from deep in the woods – and then I understood I wasn’t listening to one animal, but several. But there was no harmony in their singing, that’s for sure.

  2. OK – I win – I split Psi – but I cheated – I used the 15-inch! 😉

    . . . and it still was a challenge, though not a real big one. What really struck me, though, was how similar this group is to Polaris. You have a very similar separation and the magnitude range is close – greater with Polaris, but the secondary stars are about the sameso the general impression is the same – except the secondary itself does split.

    What was challenging was learning how to ignore the primary. But to my great surprise, I found I could do it. At first I got so desperate to get the primary out of the picture that I let it drift out and tried to look at the secondary alone – and for a second or two it really lit up – but that was too brief.

    Then suddenly I just got the feel for how to look directly at the secondary and pretty much ignore the primary and that’s when I found the split almost easy. The highest power I could use on that scope tonight was 188 delivered by a 9mm Nagler. That’s what I first split it cleanly with. But later I found I could split it at 130X with a 13mm Nagler.

    The satisfaction of really sharp star images is missing with that scope, so I did try it with the 127mm AR-5. No go. Given your skies and your quality 6-inch Jaegers refractor, you may be able to split it. But I wasn’t coming close with the 5-inch. Of course, it would have been a bit better if it had been higher and the air steadier – but again, I will be surprised if I ever split it with much less than the 15-inch.

    And no, John – I know what you’re going to ask – no I did not even try to find the 14th magnitude star.

    • OK – Greg is first, and so far I’m not even second.

      I went out to give Psi another try a couple of nights ago, but I had to wait for planet earth to rotate on its axis far enough to put this portion of Cassiopeia into view.

      So I looked at other things and made threatening gestures at the ominous clouds that passed through every ten or fifteen minutes. I was using my AR-5, a 127mm F9.3 achro, and generally having a pretty good night, other than those irritating stray clouds.

      About 2AM, I looked up and could see Psi and Iota Cass just coming into view on the west side of the fir trees that block my view to the north.

      So, leaving Jupiter behind, I turned the scope toward the north, found Psi in the finder, and took a look in the 14mm (84x) eyepiece. I could see the primary, and the pair of secondary stars could just be glimpsed. I switched to a 10mm eyepiece (118x), and could see the pair as a single unfocused star.

      Now it was time to make the move. Into the focuser went a 7mm ortho (169x). I reached for the focus knob, slowly turned it until the focus improved —-

      and they faded from view. Gone. As in not there. At all.

      I looked up from the scope and a solid layer of clouds had moved in from the north and rapidly taken possession of the sky. In less than five minutes, every star in the sky was gone.

      It could have been worse. The coyotes at least had the sense not to laugh.

      But I’ll be back.

      • September 12th, 1AM

        Tonight, it’s me, Klaus, the six inch F10 refractor, and Psi once again.
        I tried the previous night with the AR-5 once more and still no luck. The two faint companions were a blob of unfocused light that almost resolved, but never quite made it. Increasing the magnification just made the glare from the primary worse.

        So, after looking at other things once again while waiting for Psi to move into position, I turned the six inch scope to it, slowly brought the 18mm Radian (84x) into focus, and there they were – two very small pinpoints of light clearly resolved and separated. Despite how small they were, I could easily see that one of the two was slightly brighter than the other one. I really didn’t expect it to be so easy – I imagined it would take quite a bit of magnification to resolve them. Seeing was very stable, though, which eliminated a lot of the difficulty.

        I switched to a 14mm Radian (109x) just to make sure my imagination wasn’t at work and confirmed my observation. Then I tried a 5m Tak LE (304x), but that was too much of a leap. I could make out the two fainter stars, but they were so overwhelmed by the glare that it wasn’t a view worth staying with, so I went back to the 18mm Radian.

        There is really something satisfying about finding the minimum magnification for resolving a pair of stars. It’s a pleasure to see the optics separate all those photons into distinct points of light that are so close they’re within a photon’s width of merging into one another.

        And the color of the primary this morning in the six inch refractor was fabulous – a very deep orange that contrasted nicely with the black sky background.

        The coyotes hadn’t given up either – most of the night, there was a chorus of howling and yipping off in the distance. Saturday night – party time, no doubt.

  3. Iota to the Edge!

    My Celestron EdgeHD 800 OTA arrived yesterday,a just a few hours before sunset and with high clouds moving in ahead of a front. Still, i thought I could find some sucker holes – and did, and boy was I pleased!

    In the hype the Edge is described as “an aplanatic Schmidt telescope optical tube assembly designed to produce aberration-free images across a wide visual and photographic field of view. Superior edge performance creates rounder, more pleasing stars and improves resolution and limiting magnitude when compared to telescopes of equal aperture.”

    Uh huh! My first look says it lives up to the hype. I say that with caution because I did not have time to set up anys copes for comparison and I had darned good conditions despite the clouds moving in. So take these first impressions with ahealthy grain of salt – make that a tablespoon! 😉

    I tried some easy stars first, Like Almach and Polaris and I was impressed. Then when the clouds gave me a break in the right direction i decided to really challenge the Edge – Iota Cass was in the clear now, so I went to it. A dancing blob at low power with the 24 Panoptic – but oh my, at somewhere around 12.5 I had a split and I pushed it to 5mm with a Tak LE (400X) and was simply mesmerized.

    Three or four bright diffraction rings from the primary – yet the closer of the two companions shone through those rings and was easy to pick up as a nice round dot.

    The more distant companion, of course, didn’t have to contend with the primary. What’s more, my alignment of the GEM mount with the pole is very rough and so eventually as I made some notes Iota started to drift out. I came back to the scope and saw that it was now all the way to the edge of the field and still perfectly split – looked as good as it did at the center of the field! That says something for both the scope and the Tak eyepiece. And i watched it slip over the edge with the primary winking out first – JUST INCREDIBLE!

    So refractor-like stars with a SCT? I hesitate to make that claim. It seems outrageous. But it certainly seemed to me like I was getting refractor-like star images – smooth little bullet holes in the velvet background – and contrast superior to anything I’ve seen in a SCT before.

    Maybe it was the night. Maybe it was the long stint of bad whether and so a lack of photons. But I can’t wait to get out there again and see if my first impressions hold up.

  4. August 27th, 2011 1AM

    I decided to take another look at Psi Cassiopeiae this morning, since it had been almost a year since I last saw it. And I thought I might as well make a sketch of it while I was there, which is now included above, along with the latest statistics from the Washington Double Star Catalog.

    Based on last year’s experience, I knew I was going to need the six inch f/10 refractor — even five inches of aperture failed to be enough for both Greg and I.

    And, just as it did last year, it fell right into my lap — the larger aperture makes it a breeze to split the tenth magnitude “C” and “D” companions. As I was sketching, I made a few notes — one of them was that I had a very slight split with the 18mm Radian (84x), which duplicates what I did last year. But the little leap up to a 14mm Radian (109x) was just enough to put a narrow slice of black sky between the two stars, and that seemed to enhance the light blue color I could see in each of them.

    I also see I tried a 5mm Tak LE (304x) last year, but had to give it up because of poor seeing. I didn’t try that much magnification this time, mainly because the view in the 8mm Radian at 190x was just too good to give up.

    And it even drew a slight Psi (ψ) at first sight.

    It was well worth the return trip, too!

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