7 doubles + S Crb - 13/7/22

Hello everyone. 

What a marvellous evening I had with both my refractors – the William Optics (WO) 158mm f/7 and the WO 70mm f/6 – in my back garden on Wednesday 13th July 2022. I had a truly enthralling evening up to midnight. Every one of my eyepieces was used – from the 38mm in my small apo up to 374x in my main scope. My skies were almost totally clear throughout. 

As ever the famous double star website www.stelledoppie.it was used for the double stars. Please browse if you wish. 

Sunset occurred at 21.47 Irish Summer Time (20.47UT). Air temperature was 15˚ Celsius. Winds were mostly light – 15kms.  

1. I had memorised the position of Arcturus in relation to a neighbour’s tree. It was relatively easy to find in my WO 70mm at a mere 11x. But this time I found Alpha Boӧtis at 21.22 IST. That’s a full 25 minutes before sunset! I must try and see it at an earlier time in the future. At 40x in the main scope I did notice a very slight golden colour. Great start. 

2. Of course it is my traditional practice to look for Izar (Epsilon Boӧtis) next. Yet again I had a clean separation at 112x. Sadly I didn’t have clear skies after midnight. www.met.ie promised thick high cloud at 1am; and they were 100% correct. So no colours for STF1877 this time again. 

3. Pi Boӧtis led the way to some other excellent double star systems in the same area. But I started with this magnificent uncertain double that is otherwise called STF1864. There is a nice C companion but it is optical. Magnitudes: A = 4.9. B = 5.8. C = 10.6. Sep’s = 5.4” & 127.4”. PA’s = 114˚ & 164˚. In the past I have separated A & B at 40x. But this time they were both touching with my 158mm refractor. However at 112x the view was stunning; and I also noticed that the primary had a very pleasant blue-white colour. Its spectral class is B9 after all. Both B & C are white to my eyes. 

4. I moved the scope past Omicron Boӧtis and reached Xi Boӧtis (STF1888) and it is a true binary. Magnitudes: A = 4.8. B = 7.0. Sep = <5.2” and getting tighter every year. PA = 294˚ and that figure is decreasing. No separation at 40x once again – the 2 stars were touching. But what a sight at 112x. Not only were the 2 stars split, I was particularly mesmerised by the 2 star’s colours. Their spectral classes are: G8V and K5V. Intense yellow and strong orange. They remind of a tighter version of eta Cassiopeiae. These last 3 doubles are definitely spectacular for both beginners and experts alike.  

The following doubles are all new to me. 

5. A guy on www.cloudynights.com issued the challenge of splitting the true binary STT 288 some time ago. Magnitudes: A = 6.9. B = 7.6. Sep = <0.92”. PA = 154˚. As I stated earlier I used all my eyepieces. I found STT 288 very easily at 40x and increased my magnifications bit by bit. At 225x something started to happen. The star wasn’t round any more. At 280x I could see there were 2 stars touching at the correct PA. Transformation occurred at 320x – definite split! But I still used my 3mm Radian to complete the job. It was evident that my seeing conditions were rather good. I was also very pleased the wind was getting lighter at the sky got darker. Great joy was had with the Otto Struve double STT 288. Has anyone else tried it?

6. KU 107 is a delicate optical double not far from STT 288. Magnitudes: A = 9.8. B = 11.0. Sep = 57.6”. PA = 358˚. At first I used 112x on this chap and I noticed that A is a K0 slightly orange star – quite nice. Then I found there was no problem seeing both stars at 40x. KU stands for Karl Friedrich Kϋstner (1856-1936).   

7. STF 1902 is very close by. It may be an uncertain double, but is very easy to find and split. Magnitudes: A = 9.0. B = 9.6. Sep = 26.2”. PA = 191˚. Easy split at 40x. At 112x I noticed that A is (G5) decent yellow. B is white. 

8. My last double star is HU 1155 and it is an optical double. Magnitudes: A = 9.4. B = 10.9. Sep = 4”. PA = 15˚. I had very nice splits at 112x and 140x. A is (F8) yellow-white. B is white. HU stands for William Hussey (1862-1926). 

9. I finished my observing session with S Coronae Borealis and my wife Valerie joined me. It was getting near midnight at this stage. I found S Crb so easily at a mere 11x in my small refractor. I estimated its magnitude on www.aavso.org as +5.4. The star was a very nice orange - though not carbon orange. There are plenty of field stars surrounding S Crb. My true field of view is 6 degrees. I used 50 Bootis (mag = 5.5) and Chi Bootis (mag = 5.3) as comparison stars. With my main refractor at 167x S Crb looked very good indeed. I must return to it when the skies clear again. It's most extraordinary that this star normally goes brighter than 5.8!
www.aavso.org have now adjusted its magnitude to +5.3. I'm sure many an astronomer is wondering what is going on.  . But as far as I'm concerned a lot of Irish amateurs ought to check out S Crb. 

Oh! By the way, Finbarr, eta Crb is definitely brighter than both Omicron Crb and Chi Boo at +5.0. You're 100% correct. 

While Valerie and I were observing this miracle star the ISS passed by in silence.  
And then looking out a bedroom window the closest Supermoon of 2022 was extremely low in the southern sky. It's called the Hay Full Moon.  

The midnight church bells rang out and the clouds covered the whole sky. 
It was time to head for bed. 

Clear skies from Aubrey.  

Another super report Aubrey, and thanks for your verdict on eta CrB. It does look like the visual mag info on Stellarium (at least on my version of that program), and elsewhere, needs to be updated.

Continued clear skies,
Finbarr.

Thank you very much, Finbarr!
Indeed it was a sensational night's observing. 
 
I'm now thinking about the magnitude of eta Crb. 
Could it be that when one combines the magnitudes of both stars astronomers arrive at 5.0?
But when taken individually they get the magnitudes: A = 5.6. B = 6.0. 
Amateur astronomers with large apertures can separate Eta Crb at 440x. 
Looking at records back in time on the double star forum of Cloudy Nights, no one seems to question these magnitudes of either star. 
Of course I have no hope at splitting eta Crb. 
It's just too tight.  

Let's hope we get clear skies again soon. 
My Dublin sky is crammed with high clouds. 

Best regards to you from Aubrey. 

I would say in general Aubrey that for most telescopic double stars, the brightness given is that of the combined components. Alpha Centauri for example consists of a mag 0 star and mag 1.3 star, so total mag is -0.3 which is what is given in the catalogues. Therefore eta CrB should be listed as mag 5.0 on Stellarium. But the mag of one of the components being 5.6 could well be the source of the discrepancy in this case.

Clear skies,
Finbarr.

Hi Aubrey,

That was a wonderful read...you had a great night by the sound of it. 112X seemed to be the sweet spot earlier the evening, so conditions must have improved by the time you went your 3mm...very nice!

Definitely noticing those earlier sunsets this week...then again it might be the cloud:(

I wonder when will we get another clear night ?

Hello everyone. 

It sure is nice to be back on IFAS. 
For the last 10 days my wife Valerie has had a very mild dose of the corona virus. 
As a result I couldn't get near the PC at all. 
But all is well now. Valerie is no longer contagious as of today Monday.

I wish to thank Finbarr and Darren for their additional comments to my original report. 
It's great to be back learning from Finbarr who is that little bit more experienced than I on double stars' magnitudes. 

Now, I had better do more reading here on www.irishastronomy.org  

Clear skies (when?) from Aubrey.