On 10 February 2014 I made a sketch of lunar crater Gassendi. At the time I was just starting out in lunar observing and this was my first sketch of a major lunar crater. It goes without saying that I found the task quite challenging. Yesterday, and almost two years down the road, I had the opportunity to make a new sketch of Gassendi.
At both occasions Gassendi was sketched under similar (but not identical) lighting conditions and with good seeing (4/5). This means that the differences between the two sketches are due not to atmospheric conditions or the sun angle, but rather to my experience as a lunar observer.
After many years of deep sky observing I know from experience that the hours spent at the telescope slowly increases your ability to see faint details and to observe low contrast object. But when I started out doing lunar observations I would never have guessed, that the hours spent gazing at comparably bright and contrasty lunar features, would have a similar effect. Obviously they did. My sketching techniques has improved somewhat (still a long way to go), the precision in the depiction is better, but most notably I am happy to see that my attention to detail have increased.
I will try to return to Gassendi in the years to come. Hopefully the next sketch will show some further improvements.
On normal weekday mornings there are no time for astronomical observations, but this morning the cat woke me up half a hour before the alarm was set. After feeding her I looked out the kitchen window towards the east, and was treated with Venus at it’s very best, supported by both Jupiter and Mars. The triple conjunction was set on a crispy and velvet black sky and crowned by magnificent Leo.
The magic of the moment is lost in my sketch, but at least it capture the event. Leo is drawn free hand, and the proportions are a bit off.
In addition to the observation presented above, I have sketched the conjunction on three different occasions.
Lunar features are always challenging to sketch, but some are more difficult than others. Still very much a beginner, I find highland targets close to the limb almost impossible to do justice. Or rather: I can sketch them, but the results looks like crap. As this sketch of Inghirami Valley.
The valley is adjacent to Inghirami crater (to the left in sketch) and can be found close to the moon’s southwestern limb. It is radial to the Orientale Basin, and it was formed by ejecta from the Orientale impact. At the time of the sketch it had a very squarish outline, giving the impression of at lunar airfield (without the air).
There are two additional valleys in the area, both associated with the Orientale impact: Baade Valley, just south of the Inghiram Valley and hinted at in the sketch, and the Bouvard Valley, slightly to the west.
Bailly is a libration object located close to the southwestern limb of the moon. Traditionally it has been recognized as the largest crater on the nearside of the moon, but today it seems to have been upgraded to a lunar basin (without the defining maria).
The short description in Charles Wood’s Lunar 100 list states that it is a “barely discernible basin”, and that might be so, but as a crater I found it both rewarding and quite straightforward. My observations was done under a 13.7 days old moon, which, in combination with the libration at the time, positioned the terminator on top of Bailly’s far wall, thus creating a nice framing of the view.
At first I was a bit confused by the shadow on the crater floor in front of the far wall — it seemed to be on the wrong side of the wall. My best guess is that this is an effect either of the moon’s curvature and the closeness to the limb, or of a convex shape of the floor as such. The effect is beautifully illustrated in an image captured under similar lighting conditions by Damian Perch (scroll down to B).
The three parallel strokes above Bailly B (the large floor crater to the left in the sketch) also got me wondering. I have a wage memory of putting them there intentionally, but now a week later they seem odd, to say the least. Again comparing with Peach’s image, I can’t see any structures that might correspond to my strokes. Better just forget about them.
Anyway, I found Bailly a very rewarding object, and I definitely need to return one day.
Mersenius is located west of Mare Humorum not far from the moon’s western limb. It is of average size but still rich in detail. The crater walls are broad and terraced; the floor has been flooded with lava and bulges markedly upwards in the middle.
My observation was done under excellent conditions with steady, transparent skies and favorable illumination. The terraces were prominent, especially on the western side (right i sketch). The convex shape of the floor was indicated by a soft shadow tracing the walls in the northern half of the crater. Two lighter rays were also clearly visible on the floor. (After checking up on the observation it seems that the northern and thinner ray, is a rille rather than a ray.) Several secondary craters were also seen, most notably Mersenius H on the southern part of the rim, and Mersenius L adjacent to the crater on the northern side.
Clavius is the third largest crater on the moon’s near side, and it can be found close to the southern limb. The crater is also one of the oldest, which is evident from the many smaller craters that mark the Clavius plain. At local sunrise the two larger of these — Clavius C and D — gives rise to a clair-obscur phenomena, giving the impression of two eyes staring back at you.
My observation of Clavius was done under a 10 days old moon, so I didn’t get to see the Eyes of Clavius (which only shows at 9 days). But the illumination nicely captured the dramatic landscape of the crater. When I started out the seeing was terrible, and I hesitated whether to continue or to call it a night. Eventually I decided to give it a shot, hoping that it might improve after a while. The turbulence settled somewhat as the moon rose, but it wasn’t enough to capture any finer detail.
Clavius C and D are the two largest craters just right of the center. The rim is marked by Porter (top right) and Rutherford (bottom right). The large adjacent crater towards the bottom left is Blacanus.
Clavius have also made an imprint on popular culture: In Arthur C. Clarke’s 2001: Space Odyssey American activities on the moon are centered around a base build underneath the surface of the crater plain. When Dr Floyd sets out to investigate the monolith excavated in Tycho, he takes the moon shuttle from the Clavius Base.
Below is a clip from 2001: A Space Odyssey showing the encounter with the monolith found in Tycho crater. The soundtrack still gives me creeps.
The largest gathering of volcanic domes on the moon can be found in the middle of Oceanus Procellarum and close to the ring-plain Marius. Squeezed into an area of approximately 200 km in diameter the Marius Hills contains about 300 domes, half of the moon’s known population. The domes are just a few hundred meters high and thus best observed under low sun.
The sketch was made under a waxing gibbous moon, just a few days from full, and the sun angle was perfect for highlighting the many domes. Sketching them was another matter, quite cumbersome at that. Marius is the crater to the middle left in the sketch. Top right is the end of the Reiner Gamma swirl.
In 2009 the Japanese Selene mission found what might be a sky light to an underground lava tunnel in the Hills. The Marius Pit is located close to the rightmost dome in the sketch, but since it is just 65 meters in diameter it is well beyond the resolution of my scope. A fly-over movie from JAXA can be found here. Lava tunnels might be an option for a future lunar base, and apparently there is advanced plans for a private moon mission to target the Marius Pit.