Observations - 21/04/21 & 23/04/21

Hello, one and all. 

I did some observing in my back garden on both Wednesday 21st and Thursday 22nd April with my William Optics 158 mm F/7 apochromatic refractor. 
Sunset occurred at 20.36 Irish Summer Time on Wednesday. There was a very light wind of 8 km/h which fully decreased to 0 km/h as the night continued and the air temperature went down from 13˚ to 4˚ Celsius. There was dew coming. So I ended this first session at 23.30 before conditions considerably worsened. 1. I started observing from 6.15 to 7.30 pm the 9.7 day old Gibbous Moon whose magnitude was -10.8. Its illumination was 65.5% and its angular diameter was 31.6 arc minutes. I refused to go above 112X on Wednesday night – as the seeing was not good before sunset. All the usual suspects were on view as you would expect: Copernicus (93 km) and 2 of its central peaks, Montes Carpatus (400 km wide), Gay-Lussac (26 km), Gay-Lussac A (14 km) Rima Gay-Lussac (40 km long), Eratosthenes (58 km) were all observed in Mare Imbrium. Further south in Mare Nubium (254,000 square kilometres), I observed Thebit (57 kms) and its 2 interlocking satellite craters, Rupes Recta (110 km long) which was well east from the terminator.  The centres of these 4 craters were all darkness: Bullialdus (61 km) + its 2 satellite craters and Konig (23 km). One other feature, which I have observed before, was the ghost crater of Lambert R whose diameter is 55.7 kms and looked very well at 112X. It sits immediately south of the prominent 30 km crater Lambert. 
2. I now find myself apologising for not splitting, on either of these 2 nights, the true binary BU 603 which sits below Denebola (Beta Leonis). I very much doubt I even separated it in the past. The magnitudes are: A = 6. B = 8.5. Sep = 1”. PA = 328˚. A delta magnitude of 2.5 is just too difficult for yours truly. It’s only on these rare occasions, when there is minimal wind, do I get to use my 3 mm Radian which gives me 374X, and it produced no secondary at all. I could see a diffraction ring almost right around the whole of the primary. But no sign of the secondary within that ring. Clearly it is a double for owners of larger aperture telescopes rather than my one. Sometimes we have to learn such things the hard way. 

3. So after all that, let’s move unto more pleasurable experiences. 88 Leonis (STF 1547) is a true binary and is a real thriller! Magnitudes: A = 6.3. B = 9.1. Sep = 15.3”. PA = 332˚. There has been some excitement over on Cloudy Nights regarding this double. It is relatively close by to Denebola. The spectral classes are supposed to be G0V and G5. The primary is yellow okay. But the secondary ought to be yellow too – but it’s not. It’s orange.  Burnham says the spectral classes are dF7 and dK6. The “d” stands for dwarf. And “K” stands for orange. So I reckon Burnham is correct rather than the other sources. I had no hassle splitting 88 Leo at 40X. But I increased that up to 167X to greatly admire the colour of this secondary. It is my first time to observe STF 1547.

4. A good man on Cloudy Nights encouraged me to observe Iota Leonis (STF 1536). I had informed him I probably wouldn’t as I had observed it quite a few times in recent years. However as this true binary is on my way down to a carbon star, I just thought I would observe it again. Magnitudes: A = 4.1. B = 6.7. Sep = 2.2”, PA = 91˚. Great joy was had when I split it at 112X. I had the tiniest gap between. Magnifications of 140 and 167 proved very good too for this beautiful sight. The primary is F4IV yellow-white. B is white.  

5. And so I come to my first of two carbon stars in Leo: LEE 107. It has 2 other designations which some will see as more popular: TYC 871- 104-1 or GSC 871 104. The Right Ascension is 11 hours 55 minutes 39.72”. The Declination is +12 degrees 34 minutes 48.46”. It can be found near Denebola and has spectral class is C4. It proved quite a test to find as its magnitude is +10.9. However there are 2 stars which “point” to it. TYC 868 416 (9.7 mag) and TYC 868 113 (8.8 mag). The minimum magnification I used was 112X to see TYC 871-104-1. I steadily increased up to 225X and found it as a fairly good orange carbon star. It’s my 103th carbon star overall. Lee stands for Oliver J. Lee who lived from 1881 to 1964. He worked in Yerkes Observatory.  

6. Quite near Denebola is a true binary called SHJ 132. Magnitudes: A = 6.9. B = 10.2. Sep = 39”. PA = 39”. Slight problems here seeing A & B at 40X. The 2 white stars were better viewed at 112X. A first time observation for yours truly. SHJ stands for James South and John Herschel who were good friends and they discovered quite a number of doubles between them. But seemingly only 71 doubles have the SHJ designation.

7. Finally on this Wednesday night, I found a more delightful double called HJ 3335 which is optical. Magnitudes: A = 9.7. B = 10. Sep = 6.8”. PA = 70˚. I could see one star at 40X. But what a stunning pair I could see at 112X. One star a bit higher than the other. And very nice at 140X – I refused to go higher. Anyway I saw strong haze heading my way. So I didn’t hesitate to call it a night. 


Then on Thursday night we had an even clearer night with no dew whatsoever. Air temperatures went down from 9˚ to 2˚ Celsius. Sunset occurred at 20.38 Irish Summer Time. 
I observed until 11 pm this time. 

As you would expect I started with a -11.2 magnitude gibbous Moon which was 76.2% illuminated and was that bit bigger at 32.2’ wide. I observed Luna from 7.30 to 8.15 pm. 

8. The lunar terminator had reached Montes Jura and Sinus Iridum (Bay of Rainbows). I stuck in my 112X eyepiece and I could easily see the Laplace Promontorium and the Heraclides Promontorium on either side of Iridum. But has anyone observed the 8 km crater near Pr. Laplace? I have found out what it’s called: Laplace A. The man himself Pierre Simon Laplace lived from 1749 to 1827. He was an outstanding French mathematician who was a disciple of Newton. The craters Helicon (25 km) and Le Verrier (20 km) were sitting side by side further south. 2 craters I had never observed before further were Fontenelle B (14 km) and D (17 km). They are arranged in a north south direction. Fontenelle (38 km) and Fontenelle A (21 km) I had seen before. Then how sweet it was to see the craters Delisle (25 km) and south of it Diophantus (18.5 km). Between these two Mons Delisle which has a crescent shape to it. Heading south of it is a black line which has no name. Great lunar feature all the same! Mons Vinogradov is further south which is 25 km wide. It’s quite a striking sight sitting on its own in Mare Imbrium (Sea of Rains). 2 small craters I had not observed before were Fedorov (7 km) who was a Russian rocket specialist. Another Russian man whose 9 km crater I saw was Artsimovich. 

9. One last lunar thrill I saw with Valerie was the Moon occultating 46 Leonis which occurred at precisely 21.30 local time. This individual star has a spectral class of M2, and its magnitude is +5.4. Valerie watched the star suddenly disappearing in the main scope at 112X. I made do with watching it disappear in the small 70 mm apo at 15X. 46 Leonis has a decent orange hue even when so close to our Moon. 

10. Leo has a double-double. Tau Leonis is an optical double. But 83 Leonis (STF 1540) is a true binary. Tau’s magnitudes are: A = 5.1. B = 7.5. Sep = 89.2”. PA = 181˚. 83’s magnitudes are: A = 6.6. B = 7.5. Sep = 28.6”. PA = 146˚. Great sight at 40X in my main scope. But I was delighted to see them both cleanly split at 11X in my 70 mm apo. 

11. And very near them we have my second and final carbon star in Leo: BD+02 2446. Its other designations include GSC 271 245, HIP 56405 and TYC 271-245-1. The Right ascension is 11 hours 33 minutes. 49.1 seconds. The Declination is +01 degree 45 minutes .08 seconds. Its spectral class is C3. And it does have a Johnson BV colour of 1.285. It has a magnitude of +10.2 and it was easier to see than Lee 107 alright. 40X was sufficient to see it at first. But from 112X up to 280X it came alive. I would describe it as a reasonably good orange carbon star. BD stands for Bonner Durchmusterung.  It’s my 104th carbon star. I believe there is no other carbon star in Leo and that is quite surprising for such a large constellation. 

Thank you for reading my latest report. 

Comments are very welcome. 

By the way, I have discovered a Guide 9.1 DVD map in a folder which contains a good number of doubles in Coma Berenices. Therefore I going to that constellation next. 

Clear skies from Aubrey.    

Hi Aubrey,

That's an excellent report. You've had two wonderful nights under the stars (and Moon).

Congratulations on reaching 104 Carbon stars - there is no stopping you!

I don't recall observing Laplace A before, but I have observed some of those other craters. For example, one of my last sketches of 2020 was of Delisle, and I had a look at Thebit while I sketched Hesiodus last week. 

Also, very well done to you and Valerie for observing the Moon occultating 46 Leonis - what a nice event!

Wishing you (and Valerie) many a clear night over the coming weeks so you can spend much time as possible in and around Coma Berenices.

Over and out,

Darren.




 

Thank you for your most kind comments, Darren, and to all for giving me their thank-you's!

What I find most extraordinary about the crater Laplace A is it's a very easy crater to see at all times when we observe Sinus Iridum. 
The confusion arises when we see in our lunar atlases that the crater simply has the letter A beside it. 
Further confusion is when we look at Map 10 in Rukl's atlas and notice the position of that letter A. 
I used to think it was a satellite crater of a larger crater north east of Laplace A.
But no! Who would have thought it's a satellite crater of Promontorium Laplace which is also on Map 10 of Rukl?
The fairly large 25 km crater Helicon is southeast of Laplace A. 
By the way, Helicon was a 4th century BC astronomer from Greece. He was a friend and disciple of Plato. 

Clear skies from Aubrey.  

You're more than welcome Aubrey. And having checked Map 10 in Rukl's Atlas of the Moon, I see what you mean by that 'A' crater - it's not an easy one to place.

Also, apologies for the late reply - I've had a hectic week.

Clear skies,

Darren.