Hello, everyone.
For the 15th time during the month of May 2020 I set up my William Optics 158 mm F7 apochromatic refractor and its WO 70 mm F/6 small apo on the Berlebach Planet alt-az mount in the back garden. My north is mostly up. My east is to the right. Mirror diagonals are fitted to both scopes.
I have never ever had a 15th observing session in my entire life in one singular month!!
Although there were quite a number of high wispy clouds floating around over my head, I tried to not have them disturb me in any way.
I did my utmost to observe some spectacular celestial features in the heavens on Thursday night 28th May 2020 from 20.10 UT to 22.45 UT. (Please add one hour for Irish summer time). I'm delighted to say the refractor did not disappoint.
Sunset occurred at 20.38 UT
The temperatures dropped from 12 degrees to 10 degrees at the end.
1. Venus was first of course. I keep asking myself: is this going to be the last time I will observe her? Well, it wasn't this time at all. The feminine planet had a magnitude of -4.1. She was less than 44,000,000 kms from Earth. Her angular diameter was 56.7". But what was most noteworthy was the illumination: 1.3%! I first saw Venus using my main refractor at 40X at 20.10 UT. Then my small apo picked her up at 11X. She was extremely close to the distant trees. I managed to observe Venus in reasonably clear blue sky. What a wonderful sight it was to see the extremely slender and large crescent! So now I'm wondering if this was going to be the last time I had the opportunity to see herself.
2. I found Arcturus a few minutes after sunset with it was invisible. That was through my 70 mm small apo. Its wondrous golden-orange K0 colour was good and strong as always. Now that Sirius is gone, Arcturus is the brightest star in our Irish skies. Its visual magnitude is -0.05.
3. Izar (Epsilon Bootis) came next. This uncertain binary is truly Pulcherrima alright. Magnitudes: A = 2.6. B = 4.8. Sep = 2.8". PA = 347 degrees. It has now become a standard test for me personally to try and split it at 112X. Last night my refractor succeeded yet again at this power. B sits just above A with a smidgen of a black gap in between. But seeing I was going to use more powerful eyepieces later on, I observed Izar at magnifications 140X, 167X and 225X. It was very obvious my sky conditions were improving all the time in this area of the sky. The spectral classes of the 2 stars are K0 & A0. Yellow-orange and slight blue are the colours I see.
4. Then it was high time to head off to Corona Borealis. Some of these doubles I have observed before in recent nights. Omicron Coronae is a good star to start from before we go to more exotic doubles. It is an optical double with magnitudes: A = 5.6. B = 10.5. Sep = 144.3". PA = 343 degrees. Easily split at 40X as before. A is K0 orange.
5. Just north of Omicron is ARY 42 which is an optical double. Magnitudes: A = 9.3. B = 9.6. Sep = 95". PA = 186 degrees. No problem seeing A & B split at 40X of course - even though they are both dim. The colours had improved at 112X. The spectral classes are K5 & G5. Orange and yellow were the colours I saw.
6. Struve (STF) 1935 was close by. It is an uncertain double. Magnitudes: A = 9.9. B = 10.2. Sep = 8.6". PA = 289 degrees. This double is even fainter than the last one. But I could see A & B split at 40X and 112X okay.
7. Zeta Coronae is a spectacular true double. What a real gem! It has been about 20 years since I last observed it. Magnitudes: A = 5. B = 5.9. Sep = 6.4". PA = 306 degrees. No problem splitting it at 40X. The 2 stars are so wonderfully tight at this power. To study the colours I used 112X. The spectral classes are B7 & B9. I found the primary had the stronger blue-white. The secondary was less so. But what a joy it was reacquaint myself to it after all these years.
8. The very best is yet to come. And this is where it gets quite complex for me to find the correct way to describe STF 1964 & HU 1167. I am going to take these together. You see, both star systems share the same primary which is SAO 64821. Let's take STF 1964 first. A = 8.1, C = 8.1 and D is 9. B is part of HU 1167. Sep's of C & D = 14.5" & 15.1" from A. PA's = 90 & 84 degrees from A. C & D's sep is 1.5". The PA is 20 degrees. 40X is sufficient to split A & C. But I required 140X to see C and D to cleanly split. Now I take HU 1167. Magnitudes: A = (as before) 8.1. B = 9.9. Sep = 1.25". PA = 80.6 degrees. At 225X I was seeing the B star now and again. So out came my WO 4 mm eyepiece which gives 280X. Success! I now had a quadruple group of stars. What a dramatic climax to end my 15th observing session in the month of May!
Thank you for reading my report .
Comments are very welcome.
Clear skies from Aubrey.
