Lunar sketch 4 of 12: Riccioli

Hi All,

Aubrey had mentioned that this could be a bumper year for Irish amateur astronomy recently, and it certainly seems it could be. April continues where March left off with the conjunction of Venus and M45. It was a great event for each of us, and reading your reports from around the country added to the event for me.

Well, last night was another great April observational session. The Moon was 98.5% illuminated and the libration was favourable to observe Riccioli Crater. I had not planned to sketch this crater. Admittedly, I was blissfully unaware that it even existed before last night. However, a very thin, but rather distinguishable black line running from its rim immediately caught my attention as I scanned the terminator. I believe the name of this lunar feature is 'Rimae Hevelius', but correct me if I'm wrong.

As I increased the magnification to a 9mm expanse, which has a 66° AFOV, and then added 2X Barlow eyepiece, I could see Lohrmann, and many other craters either side of the Rimae Hevelius'. One of the nicest lunar features I have seen thus far has to be the five craters on the western side of Rimae Hevelius. These include Lohrmann M, B and F. In a way they remind me of the inner craters of 'Clavius' only nicer -  what are your thoughts on them?

As I sketched the main crater, I was stunned by how quick the shadows were changing. I started the sketch at 23:43, and by the time I packed-up at 00:27, the main crater and its surrounding environs looked quite different. For example, what appeared as a black square box with a white circle in the middle of it - on the far eastern side of the main crater - was completely washed-out by the sun's light. 

I found it quite tricky to polish-up the sketch at the eyepiece as it can be difficult to use precise movements with an eraser under a dim red light. So, I continued to work on it inside by trying to improve the shading, and lighting in and around the crater. Hopefully, I have managed to produce a sketch that somewhat reflects the actual crater. While I feel the inner crater and outer cratlets resemble what I observed, the area between Riccioli and Grimaldi I feel is is too steep. I just couldn't figure out how to flatten the slopes with my pencil and blending stump. So, if anyone has any suggestions on how to achieve that I'd love to hear from you.

Other details from last night's sketching session include:

Location: Dundrum - Bortle 8
Seeing: 6pk
Transparency 5
Instrument used: f/8 150mm Newtonian Reflector
Eyepieces: 32mm Plossl; 24mm Plossl; 9mm, and 6mm Expanse (66° AFOV), 2X Barlow Lens
Materials used: 2B, and BB graphite pencils, normal and kneaded erasers, an eraser shield, and various sized blending stumps. The image was sketched at the eyepiece, and cropped and reszied using GIMP 2.0. The sketch was photographed on my phone, and I tilted the phone to an angle of approximately 45° when taking the photo.

As always many thanks for taking the time to read the above, and your comments and feedback are always welcomed.

Stay safe, and clear skies to all.
 
Darren.

















   

Very nice.

Excellent Darren. I can't give you any advice about sketching though, I can barely draw a curtain.

Finbarr.

As ever, Darren, this is a very fine sketch!
Keep it the good work.

Clear skies,

Aubrey.

Hi Gents, 

Very many thanks for your nice comments. Glad you liked it. I can hardly believe that this the 4th installment...time really is flying by. 

Clear skies, 

Darren. 

By the way, Darren. Giovanni Baptist Riccioli lived from 1598 to 1671.
He was a contemporary of Galileo.
He was a philosopher, a theologian and an astronomer.
Riccioli was the first man to name various craters and maria on the Moon.
I also seem to remember him playing a part of the first lunar atlas.
His crater on the Moon is 146 km in diameter.

It appears you have observed Rimae Riccioli - and not Rimae Hevelius.
Sorry if that bursts your bubble, Darren.
I don't mean to give you this hassle.
Rimae Hevelius is actually inside the crater of the same name - Hevelius.
Whereas Rimae Riccioli is inside the crater Riccioli alright.
I'm sorry the lads on Cloudy Nights haven't sussed it out yet.
Of course I am responsible too for not coming to you sooner.
My deepest apologies to you, Darren.
As you know, I own a copy of Antonin Rukl's Atlas of the Moon.
It shows where both Rimae are positioned.

But I did observe the crater Riccioli some years ago -many years ago probably.
The large basin Grimaldi next to Riccioli I have seen also.
When Full Moon occurs every one recognizes Grimaldi because of its dark shading.

I'm already looking forward to your next sketch, Darren.

Clear skies,

Aubrey.