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On the Other Side of the Hill: Iota (ι) Leonis

Well, not a REAL hill.  More like a metaphorical hill.  I’ll explain, but first we have to describe the terrain.

You’ll find Iota (ι) Leonis hanging around the middle of Leo the Lion’s rear leg, just below the Leonic hind quarters.  On most charts this rear section is usually shown as a triangle made up of  2.1 magnitude Beta (β), 2.6 magnitude Delta (δ), and 3.3 magnitude Theta (θ) Leonis.  But I prefer their real names — Denebola, Zosma, and Chertan.

Leo the Lion, proudly marching across the sky. (Stellarium screen image with labels added, click on the chart for a larger view)

Uh-oh — I recognize that inquisitive stare.  It’s a  “And what might those names mean?” look.

Well, according to Burnham (volume two of Burnham’s Celestial Handbook) and Kaler, Denebola means “the lion’s tail.”   Zosma means girdle (as in belt) — BUT — according to both Burnham and Kaler once more, that’s a “transliteration” of the wrong word.  The correct word is Duhr, which means “the lion’s back.”  And Chertan means “ribs.”  Again, from Kaler.

If you let your eyes travel south from Chertan the same distance that separates it from Zosma, and just a slight bit to the east, you’ll come to Iota (ι).  If you continue to go south that same distance, you’ll come to fourth magnitude Sigma (σ)Leonis — which means you’ve gone too far.  😉

So let’s go back.

The Leo Triplet (NGC 3628, M66, M65), Iota (ι), Tau (τ), and 83 Leonis. (Stellarium screen image with labels added, click to enlarge the chart)

But hold it, let’s digress once more.  Halfway between Chertan and Iota (ι) Leonis are three of the more famous galaxies in the sky — M65, M66, and NGC 3628 — which are known as the Leo Triplet.  You can even glimpse the two Messier objects in a 60mm scope on a reasonably transparent night.  It would take very good transparency and a very sharp eye to glimpse the ghostly and mysterious NGC 3628 in a 60mm scope — it’s no wonder Messier missed that one.  But it can be picked out without too much problem in an 80mm scope or larger under dark, transparent skies.  It has to be one of my favorites — just a long, very thin, very nebulous line barely visible against the background of a black sky that’s fun to ferret out of the darkness.

Ahem.  Back to Iota (ι).  Sorry.  I’m distracted very easily.  🙂

Oh — before I forget! — included on the chart above are the locations of Tau (τ) Leonis and 83 Leonis, a very attractive pair of doubles which Greg has written up here.  See how easy it is to get distracted in this area?  I won’t even think about crossing the border into Virgo!

Iota(ι) Leonis  (Σ 1536)       HIP: 55642   SAO: 99587
RA: 11h 23.9m   Dec: +10° 32′
Magnitudes AB: 4.06, 6.71   AB,C: 4.06, 11.06
Separation  AB: 2.10″          AB,C: 331.30″
Position Angle  AB: 95.9°  (WDS 2015 Ephemerides, orbital chart and info here)
.                      AC: 346°  (WDS 2000)
Distance: 79 Light Years
Stellar Classification: F4, G3

Now I came across this one last spring (2010) and never could quite pry it apart.  I came close several times,  but it disappeared over the western horizon and melted into the sun, so I’ve been waiting for it to return this year.

A few nights ago (March 6th), I gave it another tremendous try using a Celestron 102mm f10 refractor.  The seeing was about a 3 (as in this chart at “III”), which just wasn’t quite enough to do it.  I thought I could glimpse it at 83x in a 12mm Brandon, but it – or whatever I saw – kept disappearing just as my eyes locked onto it.  I jumped up to 100x with a 10mm Radian — no luck — made a leap to a 7.5mm Tak (133x) — no luck — and then tried a 5mm Tak (200x) — and still no luck.  But I saw something at about the correct position angle, even though the image was bobbing and weaving at the speed of light — but that was all my eyes would tolerate.  They refused to participate any further.

And this is where we go over the metaphorical hill  ……  from March 6th to the night of March 7th/March 8th — to a night when for a short time the seeing was so out of this world I really thought I was on another planet.

This time I was working with my AR-5.  I started observing around 8 PM and kept at it for about three hours under fairly transparent skies and average seeing.  I took a break at about 11 PM to warm up, went back out at midnight, looked up into the sky — and saw one of the murkiest scenes I’ve ever seen.  Yet not so murky I couldn’t see first magnitude stars, and even a few fainter than that.   Hmmm, I thought, seeing can sometimes be pretty darn good in this situation.

Saturn’s yellow-orange glow was hovering in the southeast, so I turned the five inch Meade in its direction and sat in stunned silence for a good sixty minutes.  I’ve never seen Saturn from my deck at 200x when it wasn’t jumping all over the eyepiece — but this time, it was just as still as a summer night without a breath of wind.  It looked like a photograph.  I just could not pull myself away. I literally didn’t move from the eyepiece that whole hour.  Category V seeing without any question — finally!

But inevitably, the seeing finally started to slip a bit.  When I saw the rings start to waver back and forth, like a plane dipping its wings, I moved north a short distance to Porrima, which was two very well separated and very smooth globes of light — another memorable view for the memory banks.

And then it was that Iota (ι) Leonis re-entered my seeing stunned consciousness.  By this time, Leo was across the meridian and loping toward the west, so I hesitated because that part of the sky typically has poor seeing from my location.  But I thought I would give it a try anyway just for grins. 😉 😉 😉

I still had a 6mm Radian (197x) in the AR-5, so after centering Iota (ι) in the finder, I leaned over to look into the eyepiece — and darned if the secondary wasn’t peering back at me!  Just like that.  Amazing.  After all the times I’ve tried to dig this one out, it suddenly gave up without a fight.  Maybe I had worn it out.  I noticed the seeing had deteriorated a bit more, but I would still rate it a four.

The primary was very white, and I’m not sure about the secondary — some of that white light looked like it was leaping from the primary over to the secondary and then back again.  So if it was white, it was a borrowed white.  Beautiful sight, though.

About this time a chorus of coyotes went wild.  There must have been about ten of the little devils, and they were calling back and forth to each other from a couple of different locations.  As I stared at that petite point of dim light and listened to them singing and yipping to each other, I felt my adrenalin level start to increase — their energy was infectious!  I felt the brain cells crystallizing into a single thought under my frost covered Star Splitter’s hat!  I knew now that I needed something more stirring from this star!  I needed ——- more magnification!

Yes, it’s true — I was lusting for a higher quota of Iota photons.

Now — I had just written a post a few days prior to this about coaxing the secondary of Eta (η) Geminorum (Propus) out of an uncooperative sky at 83x, in which I took great pains to point out how rare it is in my part of the world to get seeing that allows me to get much past 150x, and how critical it is for success under those conditions to rely on finesse.   But as of this moment, I was finished with finesse! What I wanted now was enough  s p a c e between these two stars to drive a truck through!  Coyote music was roaring through my blood!

So I dropped a 4mm Astro Tech Plössl into the diagonal with a loud snap, leaped to my feet, and surged forward for a 295x view.  If you’re going to forge a truck lane between two stars, you gotta have horsepower.

And I saw so much bouncing and dancing and spinning and hopping and leaping and shaking and squirming  —  that I had to look away to hang onto my dinner.

Geez, so much for truck traffic.

About this time I thought I heard a low growl  ……   and the coyotes stopped.  Dead silence.

I could have sworn it was a lion’s growl, but the only lion within a few thousand miles of me was Leo  ……..     but no — no way.

Maybe it was time to call it quits.  The temperature had slipped to a very cold 28 degrees and the frost on my Star Splitter’s hat had turned to ice.  It was almost 3 AM, and I had been at this for three hours with no break, and my toes were about thirty minutes past numb and — well, hallucinations aren’t healthy when you’re all alone on a cold deck fifteen feet above the ground at 3 AM in a semi-frozen state.

So I went back to the 6mm Radian, soaked up the view for about ten minutes to see if the photons would warm me up — they didn’t — and decided to close up shop for the night.

It took a few trips to get everything moved off the deck, and the coyotes stayed quiet the whole time.   The last piece was the tripod, and as I got to the door, I set it down for a second and looked up at Leo.  That huge head was just starting to disappear behind some trees, and if I didn’t know better, I would swear I saw it wink at me.

This is what Iota Leonis looks like in a six inch f/10 refractor a couple of years after writing the post above.   The seeing on this particular night was outstanding, so I sat and soaked up the view for a good thirty minutes.   (East & west reversed to match the refractor view, click to enlarge and get the full effect).

This is what Iota Leonis looked like at high magnification in a six inch f/10 refractor four years after writing the post above. The seeing on this particular night was outstanding, so I sat and soaked up the view for a good thirty minutes. (East & west reversed to match the refractor view, click to enlarge and get the full effect).

12 Responses

  1. Hi John,

    I’ve been observing Iota Leonis over the last few weeks, on and off. I have bagged it in my 4″ f/15 a few times but only under the very best conditions. Although I haven’t compared them side by side, the extra aperture of my 5″ f/9 seems more capable at resolving this tricky system. 225x does real good in average to good conditions.

    Best wishes,


  2. Hi John, I have also been looking at Iota Leonis a few times
    recently with the 80mm with no luck I might add but your piece
    inspired me to give it another go so tonight looks pretty good
    so here goes.


  3. Hi Pat,

    Best of luck with the 80mm — that will be a heck of an achievment, but you may well be able to coax the secondary out of hiding with the Zeiss. If anything can do it, that would be it. Can’t wait to hear how it goes!


  4. Hi John,
    Iota Leonis thats one tricky double last night was clear so I set up
    just after dark with the Zeiss 80 mm, first every time I look at Leo
    I start with Gamma at 72x it was just beautiful well split two deep
    yellow stars. Right on to Iota centered it in the 16mm eyepiece
    another yellow star but a lighter yellow than Gamma of course
    no hint of a split at 72x I popped in a 10mm ortho to give 120x
    still no hint of a split I did think the disc was slightly less round
    thought. On to a 6mm zeiss ortho now there was something there
    in moments of very steady seeing I thought I could see a small
    grayish object (I could not see it well enought to call it a star)
    following the primary nearly due east of it. I then tried a 2x
    barlow with the 10mm to give me 240x but although Iota looked
    as clear there wasno improvement in the view of the companion.
    I even tried the 6mm with the barlow to give a crazy 400x and
    was suprised to find the view was still pretty clear but no sign
    of the companion. So to sum up at 200x there WAS something
    there but I could not say I split Iota yet will have to get back to
    it again, tonight is cloudy so will have to wait for a better night.
    Before I packed up I had a look at Izar, now that is some double
    one of my favourites.


  5. Just added a sketch of Iota Leonis to the post on that star, “On the Other Side of the Hill.” Caught it at 253x on a night of excellent seeing, so I couldn’t resist recording it for posterity.


  6. Hi John, beautiful sketch of Iota Leonis looking through my
    notes I see I have not split Iota yet, not sure if I used the 6 inch
    reflector on it must try next clear night.


    • Thanks, Pat.

      Iota Leonis is more difficult than the numbers would lead one to believe, but then it may be the frequently poor seeing here that gives me that impression. I wouldn’t expect you would have too much problem with it using the six inch reflector — should be possible with less aperture under cooperative seeing conditions.


  7. Hi John just back in from the telescope and having split Iota with
    the 6inch reflector at 275x . Still very tricky though, there was some thin cloud around and slight mist
    which did not help although the seeing was pretty good at times.
    To me the primary was light yellow and secondary white.
    Another double I looked at was Kappa Gemini I found the secondary
    difficult to see even though its 7″ from the primary, there is though
    4.5 mags in the difference, still it was harder than I though it would
    be.but a neat double all the same.


    • Hi Pat,

      I have a suspicion the secondary of Iota Leonis may be a bit fainter than the last magnitude listed for it in the WDS, 6.71. You’re right, it’s harder than it should be. On the other hand, it’s also possible the separation is a bit tighter than the 2.10″ listed for it.

      The same may be true for Kappa Gem. I need to take a another look at that, but someone else mentioned it being more difficult than the current data for it (magnitudes of 3.7 and 8.2 separated by 7.5″ at a PA of 242 degrees) would lead you to expect.


  8. All these posts are years old now. Is the Star Splitter group still together or, like double stars on a hot summer night, have you disappeared in bad seeing?

    • There are about 260 posts on this site, many of them covering three to four double stars. It reached the point where new material required so much research that there just wasn’t time for other things. So, it was time to move on. We haven’t disappeared, though. I still monitor the site once a day and make occasional changes when something catches my attention.
      P.S. The seeing around these parts hasn’t improved one bit in the last several years.

      • Hello John. Thanks for the reply. It’s so nice to see that the site hasn’t died. You’ve all put so much into it. As an astronomer from age 9, I’ve spent hours under dark skies observing double stars. Life interveners, first beer, then girlfriends, wife, two kids and then grandchildren but I’m retired and back to my ur-alt-hobby with a new Meade LX200 12-inch. It loves gathering light by the bucketful and some of my best challenges are trying to split sub-second doubles. Like you, we struggle here in southern UK with light pollution and unsteady seeing but the fun is trying.
        Thanks for much for your response.

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