Observations - 25/08/21 & 27/08/21

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Observations - 25/08/21 & 27/08/21 was created by flt158

Hello everyone. 

We are having a good number clear nights over Dublin recently. 
I set up my Williams Optics 158 mm F/7 apochromatic refractor in my back garden on Wednesday 25th August and again on Friday 27th August. Sunset has been happening before 8.30 pm. The air temperatures have been a rather good 12˚ Celsius. So there was no need to put on layers of clothing. All these figures are from www.stelledoppie.it and I do use printed maps from my Guide 9.1 DVD. As I have a mirror diagonal fitted to the scope my north is to the right and my east is down.  Please note every one of these doubles are within the confines of Cassiopeia – the big “W”. 

1. Schedar (Alpha Cassiopeiae) is a hugely popular optical double. Magnitudes: A = 2.4. B = 9. Sep = 70.4”. PA = 283˚. This is a very easy star to find even when Sol has only set about 30 minutes earlier. The primary’s spectral class is K0 and I see it as a good strong yellow. At 40X I see the secondary effortlessly easy at 40X – even though the main star is still invisible in my north eastern sky. 

2. Adjacent to Alpha we have what is my favourite 4th magnitude double star of the entire sky because of the beautiful colours. Achird's (Eta Cassiopeiae) first two stars (A and B) are a true binary. But C is optical. Magnitudes: A = 3.5. B = 7.4. E = 10.2. C and D are too faint. Sep’s = 13.4” and 76”. PA’s = 327˚ and 126˚. A’s sp. class is G1. B’s sp. class is K7 or M. On Friday night I increased my magnification from 40X, when Eta Cas is easily split, up to 225X to check out those hues. To my observing eye the colours are a delightful yellow, almond brown and white. The secondary is not quite fully red but is very much stronger than a simple orange. What a super double it is for beginners!  

3. All 3 components of 6 Cassiopeiae (STT 508) may be uncertain. But A and B are a real test for my refractor. Magnitudes: A = 5.7. B = 8. C = 10.2. Sep’s = 1.5” and 63”. PA’s = 194˚ and 311˚. I managed to separate A and B at 225X with my 5mm Nagler. I had the slenderest black gap at this power. All 3 stars appeared white. 6 Cas brought great joy to me. Even with that 2.3 delta magnitude difference I had no hassle splitting the secondary from the primary. Utterly marvellous! STT stands for Otto Struve (1897-1963).

4. STT 7 is a very easy triple star to split at 40X. But to make it a quadruple is going to be extremely difficult for my refractor. The magnitudes are: A = 9.2. B = 9.8. C = 8.6. D = 7.8. Sep’s = 0.9”, 48.5”, 109.7” and 155.5”. PA’s = 129˚, 259˚ and 102˚. What is particularly strange is that the A and B stars are placed between the C and D stars. On top of that it’s not going to be at all easy even at very high magnifications. I had no clean split at 320X with my 3.5mm Nagler. But success was had with my 3mm Radian which gives me 374X. I could see the 2 stars quite distinctly delicately separated. An 8” reflector might have a go at the A and B of STT 7 – if not a 10”. Any offers? Stelle Doppie tells us all 4 stars are probably optical. But I wonder about that. Can it not be the case A and B are an actual binary? Discuss. 

5. STF (Struve) 30 is an optical double star and one I came across way back in the 1990s. Magnitudes: A = 7. B = 8.9. Sep = 13.2”. PA = 316˚. Easily split at 40X as you would expect. But as I increased the magnification I never could make out the blue hue of the primary. Its spectral class is B9. Both stars were white to me. 

6. HU 507 is an uncertain double. Magnitudes: A = 10. B = 9.6. Sep = 1.6”. PA = 129˚. What a weird double this is. It’s one of those doubles when the secondary is slightly brighter than the primary. I found it very stubborn to separate. No split at 225X, but I could see there were 2 stars alright. My William Optics 4mm UWAN did the business. At 280X I was happy and contented. The only thing is I forget to look for the C star. So maybe I need to revisit HU 507 again. HU stands for William Hussey (1862-1926). 
7. ES 41 is an uncertain double. Magnitudes: A = 8. B = 11.2. Sep = 6.3”. PA = 220˚. Lovely split at 112X. The primary is F8 yellow-white. ES stands for Rev. Thomas Espin (1858-1934).  

8. HU 504 is an uncertain double. Magnitudes: A = 10.2. B = 11. Sep = 2.4”. PA = 261˚. Remarkable split at 167X. Both stars are white.
9. STF 9 is a true binary. Magnitudes: A = 9.3. B = 9.3. Sep = 20”. PA = 165˚. Why should I bother going higher than 40X? The 2 little eyes appeared side by side. 

10. ES 2577 is a true binary. Magnitudes: A = 8.2. B = 9. Sep = 66.2”. PA = 311˚. How extraordinary! A true binary – even though it has such a wide split. The 2 white stars are easily seen at 40X. 

11. And within the same 2˚ fov we have another wide split pairing. However ES 2576 is an optical double. Magnitudes: A = 8.6. B = 8.7. Sep = 77”. PA = 294˚. Easy split at 40X. But to see the colours I used 112X. A’s spectral class is M0. B’s is K2. I could make out that A has a richer form of orange when compared with B which was a decent orange. It will be interesting as to how binocular users see both fine pairs. 

12. ES 745 is an uncertain double. Magnitudes: A = 10.4. B = 10.6. Sep = 2.5”. PA = 183˚. At first I used 167X and 225X eyepieces. But then I was thrilled to see the 2 stars split at 140X. I could also see that the primary was orange-red. What a right little cracker ES 745 is! 

13. HJ 1931 is an uncertain double which was quite a bore for yours truly. Magnitudes: A = 8. B = 10.7. Sep = 22.8”. PA = 117˚. 112X was sufficient to see the secondary well separated. A though was quite a K class orange star.

14. ES 864 is an optical double. Magnitudes: A = 9.4. B = 10.9. Sep = 9.1”. PA = 168˚. I find this double quite maddening to figure. I couldn’t understand why I needed 280X to see the secondary. But there you have it. 

15. And so finally I arrive at my final double. HU 502 is an uncertain double and is listed in Robert Burnham’s Celestial Handbook Volume 1. Magnitudes: A = 7.7. B = 10.6. Sep = 2.4”. PA = 108˚. I got a very good view at 167X and 225X. But I was soon to notice I had a tighter splits at 112X and 140X. A is F0 yellow-white. B is white. With my refractor the secondary points downwards to the eastern horizon. Therefore we have the admirable teardrop effect. 

2 doubles I had no success with were ES 747 and ES 1197. I spent so much time on these two uncertain doubles I just gave up on them at powers up to 280X. Someone else can have a go. 

And I do realise there are probably one or two more doubles in the same area which I didn’t have time to try. Midnight comes all too soon, and I have to put everything away. 

Thank you for reading my report on these systems in Cassiopeia.     

Comments, images and corrections are very welcome. 

Clear skies from Aubrey. 
The following user(s) said Thank You: michael_murphy, Fermidox, Until_then-Goodnight!
3 weeks 6 hours ago #110565

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Replied by Until_then-Goodnight! on topic Observations - 25/08/21 & 27/08/21


What a report Aubrey - fair play! You really made the most of the recent clear spell. And you can definitely see the longer nights creeping in...roll on darker nights, hey? 

You always seem to have a great time in Cassiopeia. As Cassiopeia is nicely positioned at the moment, I'll give STT 7 a go during my next session - many thanks for the suggestion! 

I wonder when that'll be? 
Kindest regards, 
The following user(s) said Thank You: flt158
2 weeks 6 days ago #110568

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