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DSC-60: Beta Monocerotis – a primary with twins!

This is a DSC-60 Project observation –  for project details go here.
Beta Monocerotis 06h 28m.8 -07° 02′ 4.7, 5.2 7.3″ 132°

Hmmm… now that’s curious. The Double Star Club list has this as a double, as you can see from the above data taken from that list. The data is accurate as far as it goes, but the real charm of Beta  Monocerotis – aside from letting those words roll off your tongue – is it’s a delightful triple.  It’s like a primary with identical twins! That 5.2 secondary is a 5 and 5.3 star, as John notes in his summary table and his post found here.

Magnitude              A: 4.6            B: 5.0        C: 5.3
Separation            AB: 7.1″         BC: 2.9″
Position Angle     AB: 133°        BC: 108°

Splitting the secondary is a bit of a challenge, but the little 60/360 handled it just fine and there certainly are more difficult stars in the DSC list.  Monoceros is hardly the best known of constellations, so if you don’t know how to find this,  see John’s post which has plenty of charts. While it’s a rather empty section of sky, it’s sandwiched between Orion and his two dogs, so tracking it down isn’t all that difficult and it’s well worth the effort.

I made this observation March 1, 2011 – I think it was my first chance to use the Nagler 4-2 zoom on the Televue 60 scope – love that combination. Just perfect for star-splitting.  It’s really fun to center a close double, then watch it go from squashed, to a figure eight, to kissing, to a hairline split, and then a solid split as you turn the dial and move down the click stops.  The squashed was the 4mm setting, the figure eight 3.5, kissing, 3, a hairline split at 2.5 and a solid split at 2.

Those half stops may sound like small changes, but they’re significant. On the 60/360 scope they represent a slide from 90X, to 103X, to 120X, to 144X, to 180X – and that last is really pushing it for a 60mm scope, but conditions were very nice.  (Notice how I worked in our agreed upon terms for defining splits? That’s because we just posted them – with a neat graphic – in the FAQ. Take a look. It’s on the green tab at the top of the page.)

Again, my experience was a little different, color-wise, from John’s. I saw just a hint of yellow in the primary and  a very definite light tint of blue in the other pair – the blue certainly is supported by the B3 classification for all three components – but,of course, that doesn’t explain the yellow tint I saw in the primary. In fact these stars should all show the same color and John reported them that way, though he saw them as white which may have had something to do with the bright moonlight during his observation.  I like it better when our reports agree with the spectral classifications, but what you see is what you see. Just too many variables in this color business, as John explains in another one of those green tabs at the top of the page – “Star Colors.”


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