These are the features I observed on our wonderful Moon on Saturday night 4th April 2020 with my William Optics 158 mm F/7 apochromatic refractor between 9 and 10.30 pm over here in Dublin, Ireland.
The outside temperature was 6 degrees Celsius. As the night wore on the southerly winds got stronger and stronger.
I could not use a higher magnification than 112X. The Moon was constantly shimmering as was Regulus below it, double star 38 Lyncis, plus Venus and M45 also. So I stayed at 112X throughout my observations.
Getting back to the Moon: its magnitude was -11.7. Its distance was 359,700 kms (223,500 miles) away from us. It was 85% lit and had an angular diameter of 33.2'. The upcoming Full Moon is the largest of 2020. The Moon was 11.5 days old on Saturday night. My Lunar Atlas is by Antonin Rukl who recently passed away.
1. Straight away I observed Aristarchus but it looked very strange. The centre of the crater was dark. Herodotus was completely invisible. It normally sits beside Aristarchus. Aristarchus is the brightest crater on our Moon, but because the Sun had not yet shone inside it, the floor was not visible. The man himself lived from circa 310 to 230 BC. And he was the first man to suggest that our Earth revolves around the Sun. The Greek man from Samos certainly was way ahead of Copernicus' time. The crater is 40 km wide and 3000 metres deep. Aristarchus F (18 km) was seen south of the main crater. The flooded crater Prinz (47 km) was to the east of Aristarchus.
2. Very soon after that, I could see about 10 Marius domes peering in from the Moon's terminator. They were very conspicuous. I then observed the eastern side of the main Marius crater which has a total diameter of 41 km. The western side was barely coming through my Pentax 10 mm eyepiece. But the rest of the crater was very much in darkness. Lots of satellite craters were observed. B (12 km), C (11 km), CB (7 km), A (15 km), F (6 km), D (9 km), C (11 km), and even tiny Marius H (5 km) was visible.
3. Further south I could easily see 3 craters which are arranged in an almost perfect equilateral triangle. The largest one is Suess (9.2 km) and two of its companions B (8 km) and D (7 km). I wonder how I ought to pronounce his name. I'll have to look into that. Answer: It turns out we ought to say "Soose" as in Moose. You may argue about that one!
4. East of these 3 was a very large flooded crater Maestlin R (61 km). Its southern part is completely missing. It very much stopped me in my tracks.
5. Up to the northern part of the Moon, a very large crater was very easy to see. J. Herschel has a diameter of 156 km. John's father was William Herschel. He discovered Uranus. But there was a very weird feature to the northeast of the J. Herschel crater which looked like a very long pointing finger. Why? It's eastern side of the 68 km crater Anaximander. The rest of this crater was beyond the terminator. Spooky! Bianchini (38 km), Bouguer (23 km), double crater Horrebow (24 km) + A (25 km) are positioned at the south of J. Herschel crater.
6. Much further to the south west we have Gassendi and its 2 central peaks. There are very long faults called Rupes Liebig which are 180 km in length observed. These were quite spectacular. But at no time could I get a glimpse of Rimae Mersenius which are to the west of Rupes Liebig. I just couldn't use a higher magnification unfortunately. Never mind.
7. The floor of the crater Mersenius was seriously invisible. But Liebig (37 km) and Mersenius D (34 km) looked very good.
Thank you for reading.
Comments are very welcome.