A very interesting experiment!
I like the varied effects that you achieved here. Now you'll have us all playing out the differing combinations and possibilities!
How many different combinations can be varied from three times three here? I believe it will go beyond sheer math numbers and instead many will develop wide and varied combinations and desired effects. I especially like the one at left on black paper as that is close to what I use, with the exception that I apply much more pressure with pastels to fill in the light, then blending more at times. You have made a preliminary example of how I start my images on black paper.
I took the liberty to play with the black paper image with use of Photoshop although I am not the master of this electronic medium. I would like to see what Carlos would do with it. I used a low percentage fill to drag the paint brush in Photoshop to simulate blending a little in the crater walls to add subtle fill light in a range of greys. Then I dragged another brush (I don’t know the name of it) but it is a drop down menu at the Brush Symbols showing possibly 50 different brush tips. It is a rough scumbling-like brush, and I dragged in with bright near-snow white to fill in the area around the crater. This is only a rough example of how I would use various white to off-white pastels on black paper. I am not seeing the original photo so I’m just guessing that the angle of incidence of the light appears to be coming from the right in your images here.
I would like to see you and others take the soft pastel chalks from the middle example on the grey paper, over to the black paper image on left (try to imagine those buttery soft pastel chalks not just lightly sketched as unblended but dragged over black paper, then no less smeared, blended, etc. as where desired [and I am not suggesting 'pastel pencils' here] but rather those whole soft pastel square sticks and rounded cylinder shaped chalks that I believe many have never even held in their hands yet. I still get people emailing me after several years asking where to find them or what they are, for the medium of pastels are highly misunderstood. You can use the pencils in various colors if you like too, for sharp detailed lines and edges, but once others try this with soft pastels on black paper, it's like hallucinating into reality! You'll be hooked when you see the colors explode on black paper (like in the real black of outer space). You won't believe it until you try this.
I believe that that combination makes the most realistic effects. Not to diminish others who prefer grey graphite on white paper or similar but the white tones of pastel chalks on black render a so stunningly real effect, who could deny it? That is the method that several of us are using extensively. I know that everyone develops their own preferred methods but this just seems to be so logical for realistic effects as rendering the way the details are directly seen in the eyepiece. Applying stark white pastel chalk in positive light over black space.
Feel free to look through my gallery (7 pages) although I apologize for producing very few single crater close-up sketches. I am stuck on the whole moon picture, the bigger picture.
My CN Gallery
Thanks for posting this Uwe, as it could become a collaborative tutotrial idea in sketching that we might all participate in.