The Moon imaged with a Casio digital camera and an ETX 70 telescope

Just looking at the face of the Moon reveals the scars of the bombardment that the solar system has endured since its birth.   Of course collisions between objects are thought to have formed the planets and their moons in the first place.   Comets may have even brought us the water of our oceans.

Even though human life spans are a blink of time for the life of the solar system but we have recently witnessed a comet collision with Jupiter and several plunge into the Sun.

The Dark patches on  the Moon are frozen oceans of a rock called basalt.   Huge asteroids punched through the Moon's crust, melting the underlying rock and causing it to flood into the impact crater, creating a smooth dark surface.  But they are ancient, probably being formed when the Moon was young 3.5 - 4 billion years ago.   Since then the basalt oceans themselves have been pockmarked with smaller craters.

The crater Clavius is central in this image taken with a digital camera through a 200mm LX90 SCT.  The object that made Clavius was large enough to form a lake of molten basalt to floor the crater.   Smaller craters have have central rebound mountains whilst the smallest are empty hemisphere depressions

Large later collisions could still release enough energy to melt underlying rock and create a smooth floored crater.   Less massive objects cause a rebound of the crust similar to that caused by raindrops in a puddle.  

A crater in a glass of water with a rebound drop being ejected.   This kind of shot is easy to capture in your kitchen sink with a digital camera. 

Unlike liquids, the solid rebound of a crater's floor leaves a central mountain.  Large craters have massive walls.  Over time landslides cause these to collapse into a series of terraces.

Here is another shot from the side, beautifully showing how a central mountain is formed.   However if your going to let the World see your kitchen  it's a good idea to clean the taps first!

 Smaller impact objects only have enough energy to gouge out a crater and vapourise themselves, leaving an empty depression in the surface.  

You should now be able to recognise features of these three types of impact craters.   Let's see if you can spot them in this image.

The crater above has a smooth floor.  It has  terraced walls characteristic of the high walls of large craters.   Small impacts have left empty craters on the floor of the larger one.  But this crater was not formed on the Moon.  Nor was it formed on Mars, Mercury, Venus or the planetary moons.   In fact it was formed in my kitchen!   It's made out of plaster of Paris.  It was illuminated with an intense halogen lamp from a low angle.  Photoshop was used in reverse to how you would enhance a real Moon shot.   Start by changing into black and white mode.  Then increase the contrast.   Blur with a Gaussian filter and then add noise. You can use the gradient tool to give the effect of the terminator. Finally you can use unsharp mask to create the grain.  

You might ask why bother to create a 'fake' photo'?    You'll be surprised how much you will learn about how image processing works.  As you have the original photo you can even try recreating it.

MAKING PLASTER CRATERS

This is the model used to create the photo above.   It was a rush job.  With care you should be able to recreate a real portion of the Moon.

Cover yourself in old clothes and your workspace in newspapers.   Make a shallow tray from cooking foil.  Mix up some plaster to the consistency of cream in a plastic pot.  and pour into you tray.  Keep back a little to act as asteroids.    Add plaster to the water rather than the other way round.   That way you get the quantity you want (the volume of the water).  Jiggle the tray to level the plaster.   Use a teaspoon to drop plaster into your tray.   Experiment with different heights and drip sizes.   You will also find the depth and consistency of the plaster in the tray effect the type of craters you make.   As the plaster starts to set, the craters you make will also change.   Small 'vaporised' craters can be made when the plaster is nearly set using a blunt pencil or similar round end.   You can cut holes in your plaster surface with a cookie cutter and flood with fresh plaster.

Let waste plaster set and put it in the bin.   Don't try washing plaster down the sink or you'll block it.

On the left Nathan makes craters and on the right Nathan's photograph digitally  processed by Willam

TheMichael and Nathanael make craters