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24 Comae Berenices – easy split with any scope, but bigger sure helps colors

I “discovered” – well, stumbled upon – 24 Comae Berenice while trolling for galaxies with a 12-inch Dob. That immediately prejudiced my opinion of it – it was beautiful! A spring rival for Albireo. How had I never  seen it before? And why did I  find it so hard to find again?

24 Comae Berenices – Σ1657 – H IV 27 – HIP 61415 – SAO 100159
RA: 12h 35.1m Dec: +18°23′
Mag: 5.11, 6.33  Sep: 20.1″ PA: 270°  (WDS 2012)
Distance:  2631 Light Years
Spectral type: K0, A9

Well, for starters I didn’t know what I was looking at in that first view and I guess I am focused on this region as the happy hunting ground for galaxies so I never seriously thought about doubles here. Should have, though, because there are several. We’ll stick with 24 – aka Σ1657, though. This little gem is between the Virgo Cluster of galaxies and the Coma Berenice cluster of stars, so it’s a prime candidate for stumbling upon – especially if you like just prowling about for galaxies in  this region.  Haas lists it as a “showcase” and  “the Night Sky Observer’s Guide” calls it a “springtime version of Albireo.”  It’s still reasonably accessible in early summer. In fact,  as 24 Comae Berenices heads for the western horizon you can check out the real Albireo in the east. A couple hours after sunset  on the Summer solstice  they are both roughly 40 degrees above their respective horizons when viewed from  mid-northern latitudes.

That said, I thought it would be a piece of cake to find 24 again, but when I looked on different nights  with a 60mm Unitron, a 100mm Skywatcher ED, and  a classic RV-6 Dynascope I found myself spending much more time searching than I expected. Problem is, there are a lot of stars in the 5-7 magnitude range in this region and I ended up developing both a bottom up strategy, and a top down strategy for a star hop and I still can’t tell you which works best. Let me show you what I mean.

Two suggested star hops to 24 Comae Berenices prepared from Starry Nights Pro screen shot. Click image for larger view.

As to colors, I had the primary as yellow going to orange – I settled on “tangerine-in-bright-sunlight”  for the primary and the secondary as “summer-sky-blue” – especially if your summer skies tend towards the murky as mine do right now. But these colors screamed at me when using the light grasp of the 12-inch and they were fine in the 6-inch reflector. But they lost some of their zip in the 4-inch refractor and I was a bit disappointed with the view in the  60mm. All of which makes sense since are eyes need a lot of light to see color and when you look at the numbers, Albireo has a full two magnitudes on this pair.

Speaking of numbers, though, the spectral types of K0, A3 do confirm my color descriptions, making the colors similar to, but a bit more subdued than Albireo – that is the Albireo blue is more intense.. Use those numbers then look at this chart.

The “apparent” column is what we tend to see.

Now using the same chart, look at the colors for the Albireo pair – Spectral type: K3, B0

The 20-second split should be easy in just about any scope – in fact, I think this would make a real nice binocular double, though I haven’t tried that yet.

The colors I saw on the night I made this sketch weren't quite as obvious as when Greg looked at it, but it's a colorful pair nonetheless.   (East & west are reversed here to match the refractor view, click on the sketch for a larger version).

The colors I saw on the night I made this sketch weren’t quite as obvious as when Greg looked at it, but it’s a colorful pair nonetheless. (East & west are reversed here to match the refractor view, click on the sketch for a larger version).


4 Responses

  1. my favorite colourful double in the spring. highly recommended.

  2. Greg,
    I just viewed it last night with a SV102ED and an ES82 4.7mm for 151x. I tried several other eyepieces ranging up to 28mm, but the 4.7 gave me the most pleasant view in both shape and color. By the way, the colors I observed match the colors you mention and on your apparent color chart exactly. Also, it was pretty easy for me to find with my 28mm with a 2.7 degree fov and 4mm exit pupil. Clear skies!

    • Thanks for the report – and thanks for reminding me of this beauty – have to take another look with a new (to me) 5-inch SCT and compare the view with my 4-inch Renaissance. I know the refractor should out perform the SCT – I just want to see if it makes a significant difference to my aging eyes 😉

  3. Just added a sketch of 24 Comae Bernices to Greg’s post on it.


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