High resolution rays

Catch ray ejecta systems with a high frame-rate camera and a telescope

STEP 1

Find the right illumination for your target

Lunar features change appearance dramatically with varying illumination, and ray systems are no different. While craters look interesting when lit obliquely, ray ejecta appear far more striking – and more visible – when the Sun is high above them. To get the best images, plan your imaging sessions for nights when these features are located away from the terminator.

STEP 3

Don’t blow out the highlights

Ray systems are bright features and we need to take extra care when we set the camera’s exposure level. If you overexpose the rays you won’t capture their fine structure in detail, as the highlights will be ‘blown out’ and unrecoverable in postprocessing. A basic way to avoid this is to make sure that nothing in the frame appears near to solid white in the imaging preview.

STEP 5

Bring out the detail with ‘Wavelets’ sharpening

The image created at the end of Step 4 should be smooth, but will look a little soft, so we now need to make the crucial sharpening adjustments in RegiStax to make the ejecta details ‘pop’. Open the image and tweak the top three sliders on the left hand side of the ‘Wavelets’ tab. Pay attention so you don’t over-sharpen, where noise starts to overwhelm fine details and the view looks crunchy.

STEP 2

Use the lunar limb or terminator for focusing

Without shadows contrasting with bright edges as you’d find on obliquely-lit lunar features, focusing your camera on a ray system that’s lit from a high angle can be tricky. Point your scope over to the terminator, focus there and move back; even if the Moon’s ‘full’ there will often be obliquely-lit craters near the limb which you can focus on before framing up your target nicely.

STEP 4

Generate a smooth stack

We’re going to apply sharpening and enhancements to our final picture, so we now need to create a smooth starting image – one in which the noise ‘graininess’ that you see in a single frame is reduced. Take a short AVI-format video of your target consisting of a few thousand frames and run it through AutoStakkert! or RegiStax, which will identify and stack the best frames.

STEP 6

Use ‘Curves’ tweaks to improve contrast and definition Apply contrast and brightness adjustments in an image editor to make the ray systems stand out; the ‘Curves’ tool is good for this as it allows for greater control of which tones are being tweaked. You can duplicate the image as another layer and apply a gentle ‘High Pass’ filter; then blend the filtered layer with the original layer using a ‘Soft Light’ mode to improve the latter’s definition.