Lunar Imaging

Lunar imaging is the next easiest form of astro imaging after wide field. The Moon is only about 250,000 miles away from us and has features that can be seen with the naked eye. Just imagine what it looks like through a pair of binoculars or better still, a large telescope. Details in craters become visible as do shadows cast by those craters, mountain ranges and valleys appear, a whole host of other formations pop out as the terminator moves across the lunar disk.

These details disappear when the moon is full because, from the moon, the sun is directly overhead and no shadows are cast for us to see. But what stands out are the lunar rays, streaks of ejected material hundreds of miles long made by crater-forming impacts.

Copernicus Ray System
Copernicus Ray System

If you want to image these lunar features in detail you will need at least a telescope and mount ( let’s assume a mount came with the telescope on purchase ) and a camera. These days even a phone camera with 5 plus mega pixels will give good images with practice. Set up the telescope, point it at the moon, focus on a crater till it’s as sharp an image as you can get, hold your camera or phone to the eyepiece of the telescope and press the button. BINGO you got your first moon picture. But it looks a bit distorted, not at all like what you see through the telescope. This is because no matter how still you hold the camera, when you push the button you move, blurring the image. Better still is not to hold the camera at all but have an adapter that will hold the camera and telescope together. If you’re using a DSLR camera you will need a T adapter and nosepiece, this gives the possibility to use neutral density filters to reduce the bright glare of the moon. You will also need a remote shutter release so you don’t move the setup by pushing any buttons.

Already the kit has grown from telescope and camera to having an adapter, maybe a filter as well and release cable too.

That’s how I started my lunar imaging and sure enough the equipment I used grew until I got to the setup I use now.

I’m going to be honest with you; the moon is not my favourite subject to image. I like deep sky imaging and the moon is the killer of deep sky work; it’s like having a 500 watt light hanging in the sky drowning out the faint light from these distant objects. But it is worth imaging when the opportunity arises.

This is the equipment I use for Lunar imaging– Sky Watcher NEQ6 Pro Mount with Rowan astronomy belt drive mod and Axiom Astro EQ6 Wedge, Altair Astro 8 inch F8 Ritchey Chretien telescope, 3x Barlow (optional ), Infra Red Pass filter and ZWO ASI120MM camera plus a laptop to run the Firecapture Capture Software for the camera and also AutoStakkert and Registax 6 Software for post processing the image.

Everything I use except for the Belt Drive kit and EQ6 Wedge was bought 2nd hand and the Software is free to download.

Here are some of the images.

 

 

 

Camera and Nosepiece
Camera with 1 1/4 inch Nosepiece fitted

The Camera with nosepiece fitted goes into the telescope where the eyepiece would go, this is your electronic eye.

Once  you are setup you will need to focus on a prominent feature ( a crater with good shadow effects, say ). You will be looking at the computer screen so you can zoom in and get a really sharp focus. Make small adjustments to the telescope focuser and leave a few seconds between adjustments for the scope to stop wobbling – this is called settling.

You will have to make adjustments to the settings in Firecapture ‘Exposure’ ( longer exposure time = lower frame rates ) and ‘Gain’ ( higher gain brighter image but more noise ) so that the image is not too bright and that you get a reasonably fast frame rate 30+ frames/second is good. This is so that you capture as many good images as possible in the fleeting moments of good seeing.

Once you’re happy with the focus and capture settings, start the capture run. Capture about 60 – 120  seconds worth of data ( 30 frames per second multiplied by 120 seconds capture time = 3600 images made into a movie – yes you just made a movie ). You can change file types in Firecapture, but AVI is best for now. This movie will be loaded straight into Registax to be processed into a final image, or loaded into AutoStakkert for stacking and wavelet sharpening in Registax.

Both AutoStakkert and Registax will take the best frames from the movie and stack them together to produce an image that is clearer than any single frame. Wavelet Sharpening will enhance the final image, but don’t go too mad with it as you’re aiming for a realistic look.

 

 

The moon is not just a drab grey ball in the sky. If you image the moon with a DSLR camera you can actually bring out colour in the processing of the image by increasing the saturation, while not strictly the true colour of the moon  these exaggerated hues can be used to map the composition of lunar rocks from a distance. Dark blue for instance means that it is richer in titanium-bearing minerals, pink colors are indicative of the iron-poor and aluminum-rich feldspars, orange and purple regions relatively poor in titanium and iron.

Moon Colour
Moon Colour

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