Observations - 25/05/21

Hello, everyone. 

I was 61 years of age yesterday (25/05/21) and there was a mostly clear night occurring. 
So where else would you find me? Only in my back garden with my William Optics 158 mm F/7 apochromatic refractor of course. I did my observing from 10 pm to midnight. Sunset happened at 9.34 Irish Summer (Local) Time. And my wife joined me to see these marvellous doubles in Boötes.  The air temperature was 8˚ Celsius at the start of the session. The wind was about 13 km/h. Mr. Musk was very busy too as there were quite a number of his satellites flying around south of Boötes. 

My figures for the doubles are from www.stelledoppie.it as per usual. 

1. Before my good lady joined me I pointed the scope at Arcturus. It is by far my favourite bright star. Its golden colour is good and strong shining at -0.05 in magnitude. Its distance is 36 to 37 light years from us and the spectral class is K. 

My wife and I admired the rest of these doubles. 

2. Izar was of course next. Again I was getting moments of separation at 112X. But 140X and 167X are always far better at splitting Epsilon Boӧtis. The colours were the usual yellow-orange and smalt blue especially as the night had become darker. 

3. STF (Struve) 1785 is a true binary which I found enormously attractive. During May 2020 2 amateur astronomers were discussing this double on www.cloudynights.com . And they were both very excited by what they saw. Magnitudes: A = 7.4. B = 8.2. Separation (Sep) = 2.7”. Position Angle (PA) = 191˚. The spectral classes are: K4V and K6V. I was greeted by 2 not overly orange stars but both proved to be very beautiful in their own right in an almost straight up-down positioning. Both Sissy Haas and Mr. Burnham have STF 1785 in their lists and I can see why. I have one question. Because of the “V” in the spectral classification, am I correct in stating both stars are roughly the same size as our Sun? I shall look forward to a reply to that. By the way, the distance of this binary is less than 44 light years away. 

The rest of these doubles are near STF 1785. 

4. A 568 (Robert Aitken 1864-1951) is an optical double. Magnitude: A = 10.2. B = 11.2. Sep = 2.6”. PA = 321˚. I was somewhat surprised but very happy to get a split at 112X without any bother at all. Even though there is a full magnitude difference. 140X and 167X were also very good. The primary did have an F5 yellow-white hue. 

5. STF 1793 is an uncertain double. Magnitudes: A = 7.5. B = 8.4. Sep = 4.8”. PA = 243˚. Before I observed this double, I was wondering if my scope would split it at 40X. Well, do you know what? Indeed it could! However I did observe it at 112X too. I found the primary white, but the secondary had a slight blue shading. Very nice!

6. Finally, my last double I observed is not an exciting one. Sorry! HJ 2688 is an optical double. Magnitudes: A = 9.9. B = 11.5. Sep = 30.3”. PA = 293˚. I could only spot B at 167X. Of course at that stage there was too much space between the 2 stars. The primary is K2 slight orange. Nonetheless I would have to state that HJ 2688 is placed in a nice region of the sky with plenty of field stars nearby. 

That’s the end of my report. 

Comments, corrections and images are very welcome. 

Clear skies from Aubrey.           

Hi Aubrey,

That's a great report from last night. Delighted you and Valerie were able to celebrate your birthday by observing the night sky together.

Like you, Bootes brings me much joy - there are so many nice objects in and around the constellation. And you have brought a few new doubles to my attention. Fair play!

Clear skies,

Darren.

 Because of the “V” in the spectral classification, am I correct in stating both stars are roughly the same size as our Sun? 

I had to do a quick refresher course on that Aubrey, but you're right. That V refers to luminosity class and in this case is a main-sequence dwarf like the Sun. More info here -

courses.lumenlearning.com/astronomy/chap...nd-cosmic-distances/

Clear skies,
Finbarr.

Hello, Darren. 

I did not know our Sun can be considered a dwarf star and I do know it always was a class V star.
I always thought it is an average sized star. 
Indeed our Sun's spectral class is G2V. 
In Burnham's Celestial Handbook, there is another smaller class of star called "Subdwarfs" and there are classed as VI. 
So they must be smaller okay. 
It only goes to show yours truly still has many things to learn. 

However I very much thank you for providing us with this link. 

Clear skies from Aubrey. 

Hi Aubrey,

Very many thanks for your message, but I believe it's Finbarr who deserves the credit as he's the one who provided the info. 

Clear skies, 

Darren.