Lunar imaging

Peering at the Moon through a telescope or a pair of binoculars is an incredible experience. I will never forget the first time I pointed my scope at our natural satellite: as I approached the eyepiece with my eye, I became speechless, and my jaws slowly dropped…it was love at first sight!

I soon became addicted as I went on for months observing the Moon, tracking its craters, valleys, maria, and all of its beautiful features. Until one day that wasn’t enough anymore: I wanted some cool pictures to show to my friends and family, and that’s when my astrophotography journey began.

Read my article about the Moon by following this link: The Moon.

For many like me, in fact, Lunar imaging was the first dive into astrophotography. This is because it is quite straightforward, it requires simple gear, and can be done literally from everywhere, including heavily light-polluted cities. There are a few things that you need to know about the Moon, however.

First, from Earth we only see one side of the Moon. This is because the time the Moon takes to complete a spin on its axis equals the time to complete an orbit around Earth, which always leaves the same side of the Moon facing us. This phenomena is called “tidal locking“ and it’s more common than you’d think in the universe.

Another important aspect to consider is that our satellite is observed in phases: depending on where it is positioned compared to the Sun and Earth, we see a different portion of its surface lit. While pictures of a Full Moon are quite suggestive, the best time to image the Moon is actually when around half or less of the disc is lit. This is because the contrast increases, and more details and features are revealed.

Now let’s see in detail the technique I use to image the Moon, using only free software. For clarity, I divided the process in three phases.

Phase 1 – Capturing

In astrophotography this is the most crucial step of the process, for obvious reasons: there’s little you can do in post-processing to fix a dull image, so focus is paramount and must be spot on. Take all the time you need to reach perfect focus, or anywhere near that anyway, and your efforts will be rewarded. Using a Bahtinov mask (focus mask) on a bright star is usually the more efficient way to do that.

The second vital aspect is “seeing” – the effect of fast-changing, turbulent airflows in Earth’s atmosphere that can make an image look blurred or distorted. Sadly, there isn’t much you can do about this apart from sitting tight with you finger ready to hit the record button as soon as the live-view image on your screen gets clear.

Imaging the Moon in infrared (IR) using an IR-pass filter and a mono camera helps you reduce the effects of bad seeing. Also, recording more than one video obviously increases your chances to get a good image out of your session, after all it’s called “lucky imaging” for a reason.

For planetary and lunar/solar photography the most widely used software is SharpCap or FireCapture. Both are free, work great and have pretty much the same functionalities. Personally, I started with SharpCap and never changed thereafter.

I record my videos in *SER format, which is more complete and easier to work on than *AVI or other formats. I typically keep gain and exposure low (but not too low) to avoid “burning” the image. Remember: you can increase exposure and brightness in post-processing, but you can’t fix an overexposed image!

Depending on the atmospheric conditions and camera performance, I generally capture various videos of several minutes each, to get somewhere between 10,000 and 20,000 frames. This should guarantee good results.

Note: Whether or not you can fit the Moon in your field of view depends on your gear. Using a telescope with a long focal length or a camera with a small resolution (or both), you may get only a portion of the Moon in your field of view. Don’t worry though: luckily there’s a way to get around this, thanks to a free Microsoft software called ICE (Image Composite Editor). All you have to do is capture some more videos, one for each area of the Moon and continue as usual (more on this below).

Phase 2 – Stacking

Once done with the capturing phase, I load the videos one by one into AutoStakkert!3, a free stacking software that analyses the video’s individual frames, giving as a result a diagram with the overall quality of the video.

Based on this graph, I choose the percentage of total frames that I want to stack (usually somewhere between 5% and 20%). The software then chooses the single best frame (the reference frame) to which all other frames are aligned a stacked upon.

When the job of AutoStakkert!3 is over, the result is a single final image made of the video’s best frames. Generally, these images look a little blurred and certainly nowhere near the amazing picture you were expecting; nothing to worry about, this is where post-processing works its magic.

Note: If you weren’t able to fit the Moon in your field of view and you had to take several panels, all you need to do now is repeat this process for each video you took. You’ll be then left with several stacked images that you can load into ICE, which will stitch them together for you using its advanced AI and will give you a final image made of all the individual panels. Look at the photo gallery below to get a sense of the process.

Phase 3 – Post-processing

When it comes to Lunar imaging, I do most of the post-processing in GIMP, a free software that looks a lot like PhotoShop, but first I use Registax and its wavelets functionality to sharpen the freshly-stacked image and bring out as many details as possible. Watch out this step though, it is very easy to get carried away and oversharp an image!

Once done, I load the sharpened image in GIMP and crop it to leave out any stacking artefacts and to position the Moon exactly at the centre of the image. Then I adjust the exposure and add some contrast before I play gently with shadows, mid-tones, and highlights to bring out some more subtle features.

If you used a colour camera, you may also want to balance and align the RGB. I usually adjust the colour curves to get a grey-metal surface.

Now your image of the Moon is finally ready to be shared on social media with friends and family!

I hope this guide will get you started into lunar imaging as a first step into astrophotography. Bear in mind that there are many other techniques out there, my advice is to try over and over, being creative and experimenting with settings and software until you find your own method.

To download the software mentioned in this guide, go to the “Downloads” section on this blog and follow the links.