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54 Leonis – whiter than white!

Usually when I see a white star I detect a hint of blue or yellow  in it – just a hint. Not with 54 Leonis. It is white – really white – or so I thought Until I read  the summary in “Double Stars for Small Telescopes” by Sissy Haas. As John says, “Impressions of star colors can vary significantly, sometimes wildly, from one observer to the next.” See “Star Colors” here for  more discussion on this.  For me, I’ll just say that Haas sees “a bright banana-yellow star” where I see “whiter than white!” Not only that, she says Webb sees it as “greenish white.”

Now this is the sort of thing that would make me want to throw in the towel – decide that I have too vivid an imagination, or that I’m color blind.  Except when I look at the scientific data I find that the spectral classification for the primary is A1. The convention is to consider the “A” stars to be white, though the apparent color – what we tend to see – leans towards blue.  Being A1 means it’s very close to the blue end of “A” – not the yellow end. An A9 star might have a slight yellow tint. So I’ll conscede that the spectral information doesn’t fully explain why 54 Leonis appears “whiter than white” to me, but “banana-yellow” to Haas. Does this mean I’m right and the other observers quoted are wrong? Of course not.  But if you don’t understand why, I suggest you read John’s piece mentioned earlier:  “Star Colors.” Meanwhile, let’s look at the relevant facts about 54 Leonis.

54 Leonis
RA:  10h 56m   Dec:  +24° 45′
Magnitudes         A: 4.5    B: 6.3
Separation          6.3″
Position Angle    111°
Distance: 290 LY
Spectral Classification: A1V,A2V

Looking in mid-December, 54 Leonis was an early morning object for me and easy to find as it’s 4th magnitude and so visible to the naked eye in my skies. But even if you’re battling light pollution, you should be able to find the bright triangle  of second and third magnitude stars that mark the Lion’s rump.  Get it in your binoculars or finder than move northwest just six degrees from Zosma and 54 Leonis is marked by a pair of sixth magnitude stars that form a triangle with it. A brief study of these two charts should make it clear.

Click image for larger view. (Labels and lines added to Starry Nights Pro screenshot.)

Click image for larger view. (Labels and lines added to Starry Night Pro screen shot.)

I first tried to split 54 Leonis with the 50mm Little Rascal, but even with using a 3mm eyepiece on this short-focal-length scope, conditions were too much for it. Under better seeing I think it would split at 68X with this little scope. But this morning I needed to switch t0 s0mething larger, the 60mm Unitron, which has a 900mm focal length, vs. the 205mm focal length of the  Little Rascal. There I got a solid split with a 10mm eyepiece. In fact, it split with a 12.5mm (72X)  and gave a hint of splitting with an 18mm (50X).

Now here’s the curious thing. With the 60mm my notes says “primary yellow, secondary a puffball.” Uh oh! Notice how those colors pretty much agree  with Haas? So where did that pesky “whiter than white” come from? The answer is by using my 8-inch Celestron EdgeHD – a SCT.  After looking with the Unitron I had switched to the larger scope because I wanted to check out nearby Porrima. And with it I had written that 54 was “very white” and its companion was “pale blue.”  I got a delicate split with a 30mm (66X) – remember, the  Little Rascal couldn’t split it with that power, but 8-inches of aperture gives you a lot more resolving power. The split was fine with a 24mm (83X)  and delightful with an 18mm (111X).

So is it whiter than white, or banana yellow?  Color, as noted, is not only in the eye of the beholder, but also in the amount of light gathered. With 54 Leonis Haas was using a 60mm – and with my 60mm we were in general agreement as to color. It was only when I switched to the larger scope that things changed.  Did I mention John has a nice article discussing this sort of thing and more? Go here 😉

Oh- and Porrima? Yes, I got a split with the 8-inch SCT at 266X – but not all that I wanted. As I reported in the voluminous comments section of the Porrima post, “. . . .there was still too much light spilling into the diffraction rings and dancing all around. It was like seeing two pearls caught in a candle flame. I could see the individual stars and black night between them, but there was light shimmering all around – over, under, and mostly beside them.” I want to do better than that – one of these nights conditions will be ideal.

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14 Responses

  1. Hi Greg, last night I was looking at some doubles in Leo when I came
    across 54 Leo. At first look I was using a 16 mm ortho in my 80mm
    scope which gives me 75x I saw a yellow primary and a blue
    companion, very nice after a few minutes I moved to a 10mm ortho.
    giving me 120x now for some reason when I looked in the primary
    had changed to more or less white and the companion seemed less
    blue after a few more minutes I switched back to the 16mm and
    the colours were back again to what I first seen maybe not as strong
    but still yellow and blue, strange. The two eyepieces were the same
    both Zeiss orthos. Any ideas. Its still a lovely double no matter
    what colour it is.

    Pat.

  2. Ah colors – there really should be some scientific sense to them, and I think there is -but there are just too many variables to pin it down for any given experience.

    Thats aid, I do have a guess. My gut feeling, Pat, is that when you increased power your eye was receiving less light, so this impacted your color vision. (That is, by magnification you were zooming in on only a portion of the image – at some point as the light diminishes you see no color – just black and white. So from that perspective I can imagine the color intensity diminishing as you describe.

    • I hope to have another look at 54 Leo tonight Greg if the weather permits,
      I will try a range of magnifications to see what difference they make.
      Its just I was suprised at how blue the secondary was when I first looked
      at it the other night.

      Pat.

      • I’m surprised too – technically, both stars should be bluish – but usually with that spectrum they show as white. Be interested to hear what you see.

  3. I just saw this exchange of comments on 54 Leonis — while working on a post on it! I didn’t realize Greg had written up this star. My experience is a little bit different, and at the same time similar, to both Greg and Pat’s, so I’m going to go ahead with it since it makes for some very interesting reading.

    I had a look at it back on March 8th, but I won’t reveal what I saw since it would spoil the fun.

    Stick around — I’ll be back in a couple of days. :mrgreen:

    John

    • Will I did get another look at 54 Leonis the sky cleared about 10.30 pm
      just as Leo was clearing the nearby trees. Tonight I was going to use
      my usual Zeiss orthos. a 16 10 and 6mm, and the same in Plossels
      of various makes. First up was the 16mm Zeiss and as in the previous
      view the colours were yellow and blue moving to the 10mm Zeiss the
      colour was still there though not as strong it was only when I droped in
      the6mm that the primary looked white the secondary still looked blueish
      which is what it should look. Now to the Plossels, starting with the
      16mm the view looked similar to the 16mm Zeiss but the colour was
      not as strong, when I used the 10 and 6 mm Plossels the primary was
      back to whitish with just a hint of yellow. I moved back and forth between
      the two sets of eyepieces for almost an hour and the results were still
      consistent in that the Zeiss orthos. showed more colour than the plossels
      this may have been because the Zeiss were slightly sharper with less
      scatter than the plossels. After about an hour I was ready for a change
      of scene so I moved to Bootes and Izar in particular, what a beautiful
      double a yellow orange primary and a blue or is it greenish companion
      just touching at 75x nice split at 120x in the 80mm scope. another
      interesting double I had a quick look at was xi Bootes stf 1888 but by
      this time I was cold and tiried so just before I called it a night a quick look
      at 54 Leonis, to my suprise when I looked in the 16mm ortho the
      primary looked white, what is going on, then as I studied it the colour
      seemed to change to yellow again which left me more confused than
      ever, but by this stage my feet were two blocks of ice (maybe this is why
      the colour changed] so time to head in to the heat and a nice warm drink.

      Pat.

      • Thanks for the detailed report, Par. Actually, icy toes and a thousand other things impacting the observer might have something to do with it – though I surely don’t know what – also it was a bit higher in your ending session, and that too, could impact it. So many variable eventually lead me back to a WYSIWYG perspective – what you see is what you get, so just enjoy it – and those Zeiss eyepieces do sound nice! 😉

  4. Hi Greg, Had a quick look at 54 last night when it was still low in the
    east and the results were the same, so as you say just enjoy it.
    I really like the Zeiss .965 orthos they are sharp right to the edge and
    very little scattered light and no refocusing when changing eyepieces.

    Pat.

  5. hello greg and pat,i had a look at 54 leo last night 4/22/2013.the night was awash with moonlight but i got a good look at 54 using my ar6 and a 5.1 epic ep..this gave me 239 x..it was an easy split with the primary a light golden yellow and the secondary a slight bluish green.i made a sketch of the ep view and its on double_star_imaging in yahoo groups with chris thuemen..i think we are close on the colors..
    mike.

    • Hi Mike, I have not observed 54 Leo this last few weeks to much
      cloud, but the colors you see are what I see in the 80mm scope.
      the 150mm reflector is somewhat different leaning towards white.

      Pat.

    • Howdy, Mike — glad to see your comment!

      I had a look at 54 Leo again last night in a Towa 80mm f/15 refractor. With the almost full moon, the colors were pretty washed out — there might have been a trace of a weak yellow in the primary and a weak blue in the secondary, but it was really hard to tell in the moonlight. Under those conditions, more aperture really makes a difference.

      Clear Skies!

      John

      • i found them to be very faint as well bt again the moon washed alot away for me..and i was wondering if you fello’s may have noticed the link i post in a msg on chris’s yahoo site? about the difference in scopes and color..,

  6. Those colors in that video are a bit misleading because they show the images as recorded through a photographic lens. The stark color contrasts visible above are not at all obvious to a visual observer.

    That’s not to say there isn’t a difference, though!

    A mirror doesn’t suffer from the CA that an achromatic lens does. And the image in a mirror-based scope will always tend to show more white — what I consider a harsher and colder tone — than what is seen in an achromatic refractor.

    Given a choice between the two, I prefer the softer tones of an achromatic lens. Especially on Jupiter, the harsh white tones seen in a reflector (or an APO) robs the image of contrast. A neutral density filter will correct that and do wonders for the contrast.

    John

    • i liken looking through the achromatic lens as looking through an old fashion coke bottle it gives it that slight bit of color don’t you think? and as with the reflector, they have less glass to look through as they use the first surface mirrows and no glass until the eyepiece. so sure there is a huge difference..but then it makes me wonder which is the the more realistic in color to the real thing! to much thinking now my head hurts!!

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