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STF 2631 in Sagitta

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#1 ssmith

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Posted 13 September 2019 - 04:52 PM

Photographed this one last night using my C9.25 and the colors were particularly vivid.

 

The primary is a G0 but I couldn't find the spectral properties for the secondary.

The color indexes for the components are +1.09 & +0.2.

 

These stars contrast nicely with the nearby orange star HD 345775 which has a color index of +1.47.

 

STF2631 Sge C9 9-12-19 mean 3fr.jpg

 


Edited by ssmith, 13 September 2019 - 05:13 PM.

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#2 John Fitzgerald

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Posted 13 September 2019 - 05:01 PM

STF 2631 in Sagitta:  I will plan to have a look next chance I get.


Edited by John Fitzgerald, 13 September 2019 - 05:20 PM.


#3 ssmith

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Posted 13 September 2019 - 05:15 PM

Thanks John - I had it labeled properly in my photo.  I corrected the title of the topic.



#4 Far Star

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Posted 14 September 2019 - 06:39 AM

Very nice photo!



#5 fred1871

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Posted 14 September 2019 - 07:40 AM

Fine image, as per usual from you, Steve...

 

The colour indexes, assuming you mean B-V, +1.09 is a fit for a spectral K-type star, +0.2 for type A, and +1.47 for M.

Interesting, if the spectrum of the +1.09 is listed as G0.

 

Could be some further investigation to do. smile.gif

Or my calibration listing is way off... frown.gif



#6 ssmith

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Posted 14 September 2019 - 10:20 AM

Fred - 

 

I went back and took a look at the Simbad reference for the special type.  They gave it a quality rating of “D” which is pretty poor (A through E with E being the poorest rating).  Also there wasn’t a bibliographic reference given.

 

I’d say it would be fair to assume that the spectral class could be way off.



#7 azure1961p

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Posted 15 September 2019 - 07:39 AM

Steve,

 

Great shot, love that blue.  As always I like the way you format your work.

 

Pete



#8 John Fitzgerald

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Posted 16 September 2019 - 10:18 AM

Last night I observed STF 2631.  Nice, easy, at 173x in my 152mm.

 

Also observed STF 2634, which, to me, was a very similar double, also looked yellow and blue.

 

Also, STF 2651, which is equal, both looked white or bluish white, and was seen at 304x.  Rather tight, and almost east and west orientation. WDS gives m8.4, 8.4, dist 0”.9.  PA 280.


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#9 Bill Barlow

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Posted 22 September 2019 - 03:32 PM

Photographed this one last night using my C9.25 and the colors were particularly vivid.

 

The primary is a G0 but I couldn't find the spectral properties for the secondary.

The color indexes for the components are +1.09 & +0.2.

 

These stars contrast nicely with the nearby orange star HD 345775 which has a color index of +1.47.

 

attachicon.gif STF2631 Sge C9 9-12-19 mean 3fr.jpg

What are the stellar coordinates for STF 2631 and ROE 101?  The STF star groups aren’t listed in the S+T pocket star atlas.  Nice photo, John.

 

Bill


Edited by Bill Barlow, 22 September 2019 - 03:49 PM.


#10 Rustler46

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Posted 03 October 2019 - 01:42 AM

As always a very nice image of a beautiful pair, Steve. About a year ago my 115mm refractor showed Σ 2631 in an interesting star field. I tried to describe in words what you so well captured with the digital camera. I might give that a try with my Sony NEX-5N or NEX-7. What ISO and exposure do you employ to capture those nice colors?

 

Here's my verbal description on September 26, 2018:

  • Double star - 8.0/9.1 magnitudes @ 4.5 arc-seconds, @ 146X, it exhibits good brightness contrast, there's a little bit of dark sky between 'em, the double forms part of an (almost) right triangle with two other maybe 10th magnitude stars, the double is at the vertex at little less than 90°, it's an interesting little double, not particularly spectacular, it almost takes averted vision to see that little secondary, after a blast with the hair dryer on the eyepiece that triangle previously described is part of a four sided kite-shaped asterism (reminds me of the constellation (Bootes), the 4th vertex is a bright field star (with a little companion of its own), an interesting field, and that little double is just right there among it all for us to see

The 4th vertex is just outside the field of your image on the right side. What I saw matches your photo except I viewed a mirror image due to star diagonal. With a Celestron-11 the primary of the pair looks yellowish. Also observed Σ 2634 (mentioned by John) the same night.



#11 ssmith

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Posted 03 October 2019 - 08:26 AM

Hi Russ -

 

Your description of the star field is spot-on.  I went back to the full frame photo and I have attached a larger crop which shows the kite-shaped star field you described.  I also flipped the image to account for the diagonal.

 

My photos were taken using 1 sec exposure  ISO 1000.

 

STF2631 Sge C9 9-12-19 mean 3fr edit2 crop.jpg


Edited by ssmith, 03 October 2019 - 08:33 AM.

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#12 Rustler46

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Posted 03 October 2019 - 01:52 PM

Hi Russ -

 

Your description of the star field is spot-on.  I went back to the full frame photo and I have attached a larger crop which shows the kite-shaped star field you described.  I also flipped the image to account for the diagonal.

 

My photos were taken using 1 sec exposure  ISO 1000.

 

attachicon.gif STF2631 Sge C9 9-12-19 mean 3fr edit2 crop.jpg

Thanks Steve for the effort. The photo shows a faint 11th magnitude star near the 4th star, which might be the "little companion" I noted. Often the nearby field stars add a lot to the interest of the doubles themselves. Sometimes it is difficult to describe in words what the eye beholds. I suppose I could make measures of separation and position angle using my Micro-guide eyepiece. Taking photos would be more efficient and would capture some color as well. Your images are always so inspiring, particularly with the added information you have researched.

 

Best Regards,

Russ


Edited by Rustler46, 03 October 2019 - 02:16 PM.

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#13 c2m2t

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Posted 15 January 2020 - 01:16 PM

Hi Russ!

I have to agree with you, I much prefer a double star placed in a bit of context. Many times there are eye catching star arrangements near by and quite often, other catalogued doubles. What I find even more satisfying is coming upon a system that is surrounded by virtually no other stars...it makes the subject double pop even more. Right away I think...it is no wonder that this pair made it into someone's catalogue. Of course one has to realize, when I say no other stars, what I need to add is the adjective, "resolvable".

 

Great discussion!

 

Cheers, Chris.


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