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Qualia's Blog

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Lyra's Doubles Doubles - A View from a City

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Qualia

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Epsilon (ε) Lyrae & Struve ) 2470 & 2474

Epsilon (ε) Lyrae, HIP 91919 - The Double Double

Along with Albireo in Cynus, the Double Double in Lyra is probably one of the most viewed multiple star systems in amateur astronomy; it is relatively easy to find, makes a good test for one's optics and scope and is rather beautiful to behold. It is estimated that the star system is some 162 light years away from Earth, separated by billions of miles and orbiting each other over a period of hundreds of thousands of years.

ε1 (to the right in the sketch) and ε2 (to the left) can be split themselves into two further binary star systems which again are orbiting each other. The component stars of ε1 have magnitudes of about 4.5 and 6, and ε2 about 5 and 5.5 and again are separated by billions of miles, each orbiting their partner over a period between 1,200 and 600 years respectively.

The two binary pairs are probably Type A, dwarf stars, something similar to Sirius, Deneb or Vega, with a mass of about 1.5 to 2 times that of the Sun. Typically, dwarf stars are young stars with just a few hundred million years of age. It is understood that there are also a number of other stars which could be part of the Epsilon star system. ε2, for example, might have another star orbiting its binary pair and collectively, ε1 and ε2 could have a total of ten other stars held by the same gravitational pull.

A City Observation

Although Epsilon Lyrae is easy to find and split into the two distinct components, splitting these again is very difficult. As can be seen from the sketch below with the 4” at about 140x, a clean separation wasn’t possible.

Perhaps I will need to re-observe and re-draw the Double Double over the winter months when seeing conditions in the city are better, but, perhaps, this isn’t the real answer. I feel that resolving this particular double doesn’t only depend upon atmospheric steadiness and dark skies, but also on my own vision which these days may not be up to scratch.

Struve (Σ) 2470 & 2474 – The Other Double Double

Σ 2470, the more northern one to the right, appears to consist of a bluish-white primary and a fainter blue companion at about 6 and 8 magnitude whilst Σ 2474, again at about a 6 and 8 magnitude, appears to consist of a reddish-yellow primary with a fainter, lighter yellow companion. Σ 2474 is said to be another binary star system in itself, whilst a 11 magnitude orbital partner, known as the C component, can be seen just left of it at about 120º.

Σ 2474, like the sun, is believed to be a Type G star about 160 light years away. Σ 2470, on the other hand, is thought to be a Type B star with about 16 times the mass of the sun and over 1,300 light years away. It follows that collectively, this ‘Other Double Double’ in Lyra, although a stunning visual binary, are not physically related and so are not true double binary systems.

A City Observation

Although not nearly as well know as their Epsilon partners, aesthetically speaking I find Struve Σ 2470 and Σ 2474 far more appealing. The double is an easy, low power split, lying parallel rather than perpendicular to each other and being less a magnifying challenge than Epsilon Lyrae, the double appears somewhat brighter whilst offering the observer a richer field of stars as a gorgeous backdrop to the colourful binary system.

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Sad I know - but I was thinking about this post on the way to work this morning and I must say I really like your 'take' on the two sets of doubles and the beauty of the Struves over the Epsilon partners.

Sometimes it's nice to forget the 'challenge' presented by splitting a double (double) and just admire the view!

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Not sad at all, Carl! I spend moments of everyday thinking about what you guys say and relate to each other. It's a healthy way of learning, I think.

With some stuff I guess I'm quite quick but curiously, when it comes to stargazing everything slows down for me. I like to sit back, role myself a smoke and admire a single sighting, or two at most, on each session. I don't know, maybe living in a city cuts back on given compromises, I mean, just seeing something is the challenge.

Thank you for your kind and thoughtful thoughts, Carl.

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My last session was a visual 'grab n go' on the 11th July. I am a newbie to splitting doubles. Here are my notes from that night specifically on the doubles that I posted on my local observing groups forum:-

"I spent a fair bit of time playing split the lyra double double at progressively lower mags. The C102 is 500mm focal length, I started with the Nagler 3-6mm zoom at 3mm & it was a relatively easy split, then I progressively zoomed out, I was still splitting it at 5mm, but it got very tough at 6mm I had to really take my time with it & not touch the scope at all, but I could just about still split both at 6mm - thats at a little over 80x mag. I read on SGL somewhere that someone managed to split it at 60x - that will be real tough for me I think, but I' like to try that on my AP - it's better optics to the C102 might help.

Feeling confident at my double splitting I had a go for the first time at splitting Zeta Herculis, but the relatively bright star looked a bit bloated by now, looking like I had a surface starting to dew up, so as hard as I tried, I can't say I made the split - it is a tougher split that the lyra double-double though. Maybe one for another night & get in early before things start dewing up. Good fun splitting doubles mind - & the zoom is a really nice tool for the job as you can establish the split & slowly zoom out maintaining the split to the point where you struggle."

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An excellent report as ever, Qualia. I really like the Struve pair as well - thanks for pointing that out; I'll have a look for this as soon as the weather permits.

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Great stuff, gentlemen and thank you for the input. I especially liked your report, Ldunn and will try again when darker nights begin. And Mark, once again, thank you so much for your kind support. Your comments and attention make everything that bit more special. Thank you.

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......hope you didn't mind me adding my post Qualia, to your blog.....I think when I did I must have thought I was posting in an open forum, not someone personal blog!!! So apologies for that, but I did think it was applicable having just done a similar observing session to yourself.

I must give the other double double that your report covers - if I can find them!! They sound really nice from your report.....thank you, this sort of sharing of experience is really helpful to discovering new things to try & to look at, much appreciaet you taking the time to post in the first place,

regards,

Lawrence

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Of course I don't mind, Lawrence. Thank you for taking the time to post. It is always a pleasure to read and even more so when what is supplied is as informative and thoughtful as your own post.

The thank you, then, is all mine :-)

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