RA: 20h 46m Dec: +15°54′
Mag: 7.2, 8.3 Sep: 6.1″ PA: 012°
Distance: 100 ly
Spectral Type: K, O
RA: 20h 47m Dec: +16°07′
Mag: 4.4, 5.0 Sep: 9.1″ PA: 266°
Distance: 100 ly
Spectral type: K, F
So we should call Struve 2725 the Dolphin’s Double-Double – it would seem so the way it pairs so nicely with Gamma. 😉
This reminded me of the Double-Double’s Double-Double – but with two significant difference. One, there is quite a contrast in terms of magnitude and two, the two pair, while bearing a real resemblance to one another, slant at different angles. But in my book it is another double-double.
In the famous – and still champion – Double Double , the stars line up like this. (All images that follow are flipped horizontally and are to different scales in order to display both pair at once. But these are reasonable simulations of what you should see in a refracting or SCT scope at a power sufficient to split them.)
The “other” Double Double, aka Double-Double’s Double-Double, aka Struve 2470 and Struve 2474, in Lyra, line up this way.
And now, the Dolphin’s Double-Double:
Splitting Gamma, as described in another post, is easy. It’s a real gem in a 60mm and in larger scopes the color comes out better. But I have not been able to split Struve 2725 with a 60mm – I tried last night after I split it easily with the ES 127mm APO, but no luck. Using th2 127mm scope and a 9mm Nagler, both pair split nicely in the same fov and they make a charming pair of pairs. Although they’re not physically related – though at about the same distance from us – it’s hard to avoid the feeling that Struve 2725 is a child – or younger sibling – of Gamma. or maybe you could think of it as a Gamma wannabe. Even though the oritenation isn’t the same, it’s close enough to the fainter little double brings a smile to your face – and when isolated in the 15-inch it really felt a lot like Gamma, though the colors aren’t as rich.
I had people looking over my shoulder last night, waiting to take a peak, so I didn’t make notes – or a detailed observation. But will return to this many times. According to the Starry Nights chart, there’s actually an 11 magnitude air in the same fov I didn’t see.
So what makes a “double-double?” To me it needs two things. First, you should be able to fit both pair in the same field of view while using enough power to split. Second, they need to all be physically related – as in the original Double-Double – or they should feel like a pair of pairs. OK, what does that last mean? It means that when you look at them they should at least look like they belong in the same picture. Yep – I’m struggling with the definition, but they all qualify in my book 😉