Struve Σ 2470 and 2474: The Other Double Double

[Nightspore]

Struve 2470 and 2474 are an interesting pair of double stars in Lyra comprising of SAO 67867 and SAO 67870 as the northern pair. With SAO 67879 and SAO 67875 as the more southerly double. Because of their similarity to Epsilon Lyrae they are often referred to as the ‘Other Double Double’.

 

 

SAO 67867 is an eighth magnitude star around four hundred and eighty eight light years away. With a spectral type A0 it is just over eight times the luminosity of Sol.

 

 

The secondary (67870) is a blue-white main sequence star three times the diameter of the Sun and around thirteen hundred light years away.

 

 

SAO 67879 is a yellow main sequence star one hundred and seventy one light years away. It is over twice the Sun’s diameter. SAO 67875 is a yellow G5 star, one hundred and thirty nine light years distant. It outputs about eighty eight percent of the energy of Sol.

 

Mirror reversed (Cartes du Ciel)

 

This little collection of stars are an often overlooked foursome. The group can appear quite dramatic when first discovered as both pairs of stars are almost parallel. They are probably best observed around a 50-80x magnification. The Struve pair are not too difficult to find as they make a loose triangle with ᵦ Lyr (Sheliak) and ᵞ Lyr (Sulafat).

 

 

 

Screenshots by courtesy of Stellarium, Cartes du Ciel, Shotwell and Ksnip.

Edited May 22, 2022 by Nightspore

[+Glafnazur]

Thanks, I'll have a crack at these when I'm next out 👍

[Nightspore]

48 minutes ago, Glafnazur said:

Thanks, I'll have a crack at these when I'm next out 👍

 

You're welcome. I saw them last night for the first time in months. They're a sign summer is coming.

[+Bino-viewer]

Yes, one for me to look at too. Thanks for posting.

I regularly check the 'main' double double, and didn't realise there was another version so close by.

[Nightspore]

3 hours ago, Bino-viewer said:

Yes, one for me to look at too. Thanks for posting.

I regularly check the 'main' double double, and didn't realise there was another version so close by.

 

You're welcome. There are a few interesting doubles in the general area IIRC.  

[philjay]

I ticked them off in my books some years ago when I did Lyra doubles from The Cambridge Double Atlas and Sissy Haas. 

I noted in the book margins "a good split, good colour". Must have another look

[Nightspore]

1 hour ago, philjay said:

I ticked them off in my books some years ago when I did Lyra doubles from The Cambridge Double Atlas and Sissy Haas. 

I noted in the book margins "a good split, good colour". Must have another look

 

I have the Cambridge Double Star Atlas as well. I probably need to use it more.

 

 

There is some debate about the colours of the 2470/2474 stars, although that's basically the same for all observing lol. I think the blue and yellow does show well even in 60mm and 72mm short tube refractors.

[philjay]

I can recommend the Sissy Haus book. Tge combo of the Cambridge and that give a pretty comprehensive guide for doubkes with amateur scopes. I also use the sadly no longer supported Skymap pro 11 which has a realky good doubles catalogue