Observations - 29th May 2021

Hello everyone. 

On Saturday night 29th May 2021 I had a very clear sky. And so I set up my William Optics 158 mm F/7 apochromatic refractor in my back garden to seek out some more doubles – except this time they were all in the northern sky. The Sun had set at 21.39 Irish Summer Time. Therefore I was discovering its position was below the north eastern horizon and creeping its way across towards the eastern sky when it rises the following day. As a result I had some difficulties sorting out what colours these individual stars possess, because the sky was never truly dark. But isn’t it all fun anyway? Any wind which had been occurring had died down completely over the course of the 1 hour 30 minutes period as I was having fun with my eyepieces. The air temperature was constant 8˚ Celsius. And Hallelujah – there was no dew!  

As I was preparing for this observing session I had noted a guy I know called John Fitzgerald over on Cloudy Nights had issued me the challenge to have a go at splitting a double star called Tyl which is otherwise known as Epsilon Draconis or STF 2603. Please read on as I give further details. One further thing I should point out at this stage: 3 of these systems were arranged in a straight line going across my sky. These were Polaris, Kappa Cephei (which has no name) and Epsilon Draconis. I did consider this very extraordinary. Plus it proved very handy to locate each system. And I have a bonus double too. 

These figures are all from www.stelledoppie.it  

1. I start with the most familiar true binary star Polaris (Alpha Ursae Minoris). Magnitudes: A = 2. B = 9.1. Separation (Sep) = 18.4”. Position Angle (PA) = 236˚.  I am of the opinion it is great fun to notice the movement of the secondary star as it seems to “revolve” around the bright yellow-white primary star month after month – even though its PA doesn’t change much if at all year after year. Because the sky was so bright there was no sign of the secondary at 40X. However at 112X I had no hassle seeing the faint white secondary star in the 7 o’clock position.   

2. Moving my William Optics 70 mm F/6 small apo to the right I arrived at Kappa Cephei where A and B are a true binary; but C is optical. Magnitudes: A = 4.4. B = 8.3. C = 10.3. Sep’s 7.3” and 170.2”. PA’s = 120˚ and 334˚. As you would expect I had no problem seeing A and C at 40X. Straight away I could see B effortlessly easily at 112X. I did some fine focusing at 40X and there it was - a tiny black gap between A and B. I had a very nice view indeed. However I must say Kappa Cephei looks extremely good at 112X. I found all 3 stars are white. It was my first time to observe Kappa Cephei (STF 2675). No blue hues at all sadly. The sky was just still too bright. 

3. And so moving the small apo again in a straight line I arrived at the true binary Tyl (Epsilon Draconis or STF 2603). Magnitudes: A = 4. Sep = 6.9. Sep = 3.2”. PA = 22˚. I required a mere 112X to fully see the delightful black gap. And I did find it a stunning sight at 140X, 167X and 225X. The primary is a very strong yellow – one of the strongest I have ever seen. The secondary I found to be a pale grey star with a hint of blue about it. Please remember my sky was still quite bright. Perhaps the secondary’s colour would have been that bit stronger in a darker sky. But I must thank you all on the Double Star forum on Cloudy Nights for encouraging me to seek out Epsilon Draconis – especially Star Alert! By the way, I did check out the pronunciation of the word “Tyl” on Google before I observed it. “Till” as in “until” is the correct way. 

4. Finally I do have a bonus double star which appears to be an uncertain double and is very near Tyl. A 865 has magnitudes: A = 8.3. B = 10.3. Sep = 2.6”. PA = 89˚. It looked rather nice at 140X. I was soon to notice it is just about split at 112X. Robert Aitken (1864-1951) discovered A 865 in 1904. Recently I successfully split A 568 which is in Boötes. That’s a bit weird, is it not? Simply reverse the numbers and I have another double split by the same astronomer and I was using the same magnification of 112X. What great fun we can have with such super doubles! 

Thank you for reading. 

Comments, corrections, questions and images are very welcome. 

Clear skies from Aubrey.    

Hi Aubrey,

What a great report, and congratulations on splitting STF 2603. Completely agree with the challenge of trying to establish the colour of some stars last Saturday - the sky stayed bright for quite some time. 

Regardless, it seemed like you had a wonderful night under the stars, although you were missed at the Sugarloaf. 

Clear skies, 

Darren. 
 

Hello Darren. 

I very much thank you for your reply. 
I am pleased that someone was missing me on Saturday night.
If all goes well, I would love to be back at the Sugarloaf some time soon. 
But as you may appreciate, if I am on music on the Lord's day, then I would have to unload the refractor whenever I get home. 
And getting the very next day at 7.30 am and to keep my mind on the job in hand is a big ask for yours truly. 
I would easily prefer a Friday night rather than a Saturday night at the Sugarloaf. 
Then I would have a sleep-in on the Saturday. 
I seem to much busier these days in church - we have had 2 pianists leave in recent months. 

Clear skies from Aubrey. 

Your more than welcome Aubrey. Safe to say we all missed you. Good point about Friday night observing sessions. If I remember correctly we usually meet up on Friday, right?

Well I'm always free on Friday night to go observing. So, I'm more than happy to go down any Friday. 

Clear skies, 

Darren.