After some cloudy periods I eventually had a very clear night on Thursday 6th May 2021.
I had set up my William Optics 158 mm F/7 apochromatic refractor on its Berlebach Planet alt-az mount in the back garden before evening dinner.
My time of observing went from 21.15 pm until midnight.
Sunset occurred at 21.03 Irish Summer Time.
The wind never died down completely. At its max it was 15 km/h.
It was very cold. The air temperature plummeted from +5˚ to exactly 0˚ Celsius.
Yours truly had 6 layers on although I never did shiver at all.
www.stelledoppie.it provide all the important figures regarding these doubles.
1. While I was waiting to see the first star appear, I thought I ought to check out Polaris (Alpha Ursae Minoris) or STF (Struve) 93 and see if I could see the secondary at a minimum magnification. It is a true binary with magnitudes: A = 2. B = 9.1. Sep = 18.4”. PA = 236˚. What is particularly fun is to see where B is at any time of the night. As we all know, our Earth is spinning on its axis once every 24 hours. Therefore Polaris B is also doing the very same. I managed to find A at 11X in my small apo at 21.19 pm. At 40X there was no sign of B in the main scope. But at 112X - hey presto, I had B straight down below A.
2. Over I go to Leo yet again. And the 1st double I wish to tell you about is STF 1417 which is near Gamma Leonis (Algieba). Rugby, here on Cloudy Nights, had informed me he thought STF 1417 are very similar to STF 1413. I had observed the latter on Friday 30th April. And I have to fully agree with Rugby. The magnitudes of STF 1417 are: A = 9.2. B = 9.3. Sep = 1.8”. PA = 270˚. Whereas the magnitudes of STF 1413 are: A = 9.8. B = 9.8. Sep = 2.4”. PA = 78˚. I find both doubles a delight to split at 112X. Both doubles’ primaries are even that little bit yellow. And so I thank you, Rugby, for encouraging me to notice the similarities of both systems.
3. HJ 476 is a true binary near Gamma Leonis too. Magnitudes: A = 7.6. B = 11.7. Sep = 24.3”. PA = 49˚. Even though the separation is good and wide, the secondary is seriously dim. To see it directly I required a full 225X. Even then I wasn’t seeing it all the time. I found myself wondering what size the stars are of HJ 476. Could A be a giant and B a dwarf star? I shall leave that question to the experts. Stelle Doppie states the system is about 1450 light years from us. The primary has a spectral class of G5. And I did indeed saw its yellow colour. HJ stands for John Herschel.
4. And so the time came for yours truly to re-observe BU 603 once again. Let’s start with the summary. BU 603 is s true binary with magnitudes: A = 6. B = 8.5. Sep = 1”. PA = 327˚. The question is at what magnification would the diffraction ring (DR) appear. And if so, would it prevent me from seeing the elusive secondary. Well at 225X there was the dreaded DR. However at 280X I could see the dim star that little bit brighter than the DR. Further success was to be had at 320X. I feel truly blessed and privileged to now confirm to you all this observation. Hallelujah! . BU stands for Sherborne Burnham.
5. STF 1511 is true binary some distance from Iota Leonis. Its magnitudes are: A = 9.3. B = 9.5. Sep = 7.6. PA = 287˚. Please notice these 2 stars are that little bit fainter than Polaris B. And with my 2” 28 mm eyepiece which delivers 40X, I did wonder would I see the 2 stars split at that power beforehand. However there was definitely no problem at all! I had the loveliest of black gaps in between. Once again I had 2 separated eyes looking at me. At 112X I could see the primary had an orange hue. Its spectral class is K0 after all.
6. And so finally, Chris from Cloudy Nights invited me to check out a double-double which is very near STF 1511. STF 1503 is a true binary. Magnitudes: A = 9.4. B = 11.1. Sep = 11.6”. PA = 271˚. A’s spectral class is F8. HJ 172 is also a true binary. Magnitudes: A = 10.2. B = 10.3. Sep = 13.6”. PA = 94˚. The 2 systems are a mere 9 arc minutes apart. What sheer delight I had when I saw both doubles split at 40X in the same fov. They were nice and tight at that point. However I was soon to discover both doubles were “buried” behind a very large tree which I do not own. Therefore the next clear night I get I will go after these 2 systems straight away and see what colours I see. But I very much have to thank Chris for informing not just me of this truly remarkable double-double.
Comments and corrections are very welcome.
And on that note I wish you all clear skies from Aubrey.