One small gap for a photographer...

…one giant leap for photographer kind*

*The sub-title may have been exaggerated for rhetorical effect

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Tuesday 16 JUly 2019 was a very significant date - 50 years to the day from the launch of Apollo 11, the rocket that was to take the first crew who would land and walk on the Moon.

It also happened to correspond with a lovely full Moon - and a partial lunar eclipse to boot. Given how much time I spend gazing up into and photographing the night sky, this was a celestial convergence I wasn’t going to miss.

But then, I live in Northern Ireland. Which means one particular thing of particular relevance to all this astrophotography related.

Cloud.

2015 - total eclipse, total success

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To be honest, ever since my first capture of an eclipsed Moon in 2015 under gloriously clear skies all night, when many other parts of the world appeared to be under cloud, my luck when it comes to cloud-free skies for lunar happenings has been pretty poor.

2018 - total eclipse, total failure

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Take almost 12 months ago, at the end of July 2018. A total lunar eclipse was due over Northern Ireland - the first since my success of 2015. It was due to rise in totality, which meant that, with the right foreground interest, we could be treated to a rather spectacular display of a red Moon rising through a deep blue twilight band beside the lighthouse at Donaghadee. 

Could be, I say. Because we weren’t. Thanks to cloud.

[Read more about this glorious failure here…]

And, to rub salt into the wound, here was the view I was getting of the Moon the night after. When there was no cloud. Typical…


January 2019 - total eclipse, partial success

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Not to worry, I thought to myself, the wait for the next go is only a mere 5 months, when another eclipse was due over Northern Ireland in January 2019. We couldn’t be unlucky twice in a row, could we…?

It was going to be a game of cat and mouse. There was a ridge of high pressure over the British Isles - this was a good thing as this weather system often brings clearer skies. But, bearing down on it from the west, like some menacing tom-cat stalking his mousy prey, was our next Atlantic depression. The approach of the warm front of the depression is often heralded by high cirrus clouds, thickening into alto-stratus as the front gets closer. The Moon was due to go into totality around 0440 hours - would the thickening cloud stay away long enough for us to enjoy the show?

In the early evening, as the Moon rose, the skies were still pretty clear. And there was that glorious orb, hanging tantalisingly in the sky, the brave mouse showing off while the cat was away. But then, it was time for bed to catch a few hours sleep before the main event.

When I woke around 0345, the sky had hazed over considerably - the heraldic cirrus had arrived - but you could still quite clearly make out the Moon. And there was that tell tale ‘bite’ taken out of it as the Moon moved into the umbra shadow of the Earth. The cat was catching up, but the mouse was still out playing…

I headed out to see a sky with ever thickening cloud. My original plans for a widefield timelapse at a local lake weren’t going to work. Plans for capturing the Moon in the company of the constellation of Castor and Pollux seemed doomed also. The best I could hope for was to try to image the eclipse through the ever thickening haze.

At first, the cirrus cloud worked in my favour. The ice crystals in this high, thin cloud can act as little prisms for the moonlight, refracting it to produce a delightful halo around the Moon (known as a 22 degree halo). And, as I stood on a bridge over the A8, that indeed was what I was seeing. This magnificent circle, with the partially eclipsed Moon dead in the centre. Throw in some car trails and I ended up with an image I was quite pleased with.

But the ominous signs are there in this shot. The lower part of the halo is faded, with the thicker cloud rapidly rolling in from the west. The chase was very much on - and my time was very much running out…

 
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The cloud got thicker and thicker. The Moon got hazier and hazier. In the end, I could barely image the Moon at all, and it was coming out decidedly fuzzy. As we headed for totality and that glorious red Moon, my luck was slipping between my fingers fast.

As we entered totality, none of the stars were visible. That was one of the things that struck me in 2015 when I saw the eclipse - just how dark it got during totality and how many other stars you could see. I was even looking forward to trying to see if I could get any of the Milky Way along with the Moon this time. But, as it turned out, not this time. I was able just about to grab images of the red Moon, but it looked more like I was shooting through the bottom of a beer bottle than my 200mm Fuji lens. 

I was resigning myself to yet another eclipse disappointment and was thinking of packing up and trying to grab some more shut eye before work in the morning. But then, something caught my eye. Rolling in from the west, charging like the cavalry coming to my assistance, was a gap. A gap in the clouds. A gap that might just be my saviour.

I quickly grabbed my camera again and got things set up, knowing I would only have the window of a few minutes to grab my shots. As the stars came out, I switched to a wider angle lens to bring in a bit more of the context of the eclipse. And there it was - the Moon, blood red in totality, with Castor and Pollux, the two twins of Gemini looking on. 

And then, just as quickly, the gap was gone, the cloud closed in again, and that was me for the night. It wasn’t all I wanted, but at least I got something this time.

July 2019 - partial eclipse, partial success

Fast forward another 6 months to last night, and that wonderful temporal conjunction between the Apollo 11 anniversary and the partial eclipse.

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Just like the total eclipse last July, the Moon was due to rise already partially in the umbra shadow of the Earth. So again, just like last July, I headed to Donaghadee to try to capture it rising beside the lighthouse there. Sadly, just like last July, that plan wasn’t to be - courtesy of that ever present eclipse nemesis - cloud. The bank of cloud along the horizon meant that there was no sign of the Moon at 2145 when it was due to rise.

But, like last January, there was still hope. Above it was cloud. But more hazy cirrus cloud. Not ideal, as it would make for an image lacking in clarity. But not a deal breaker. Would I be lucky enough to find a cloud gap before the eclipse ended close to 23.00? 

The answer? Yes - just about! The cirrus was still an issue. The lower cloud wisped all around the Moon for the rest of the night, sometimes concealing, sometimes revealing. But I got enough of a glimpse to allow me enough of an opportunity to catch an image or two. Again, it wasn’t what I had planned for, but somehow the cloud added to the mood for me, magnifying the orange glow of the light refracted by the Earth that was illuminating the part of the Moon in eclipse. 

Fifty years ago to the night, three men set out to chase the Moon, ending up being the first humans to set foot on another celestial object. Their trip was full of uncertainty and adventure. It seemed somewhat fitting last night that the Moon made me work just a little for the reward of commemorating this incredible human endeavour. 


How I created this image

1. The base image

First, given the clouds around, I wanted to make them a feature of the shot as I think they can add interest to the sky. So, my first image was exposed for both the clouds and the darker, red side of the Moon in eclipse. The settings were:

  • 200 mm zoom

  • Aperture: f/4.8

  • Shutter speed: 2 seconds

  • ISO: 320

I kept the shutter speed quite short as I wanted to keep the structure in the clouds.

Here’s how I processed the RAW file.

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2. The exposure for the highlights

Given the exposure for the darker parts of the image, the section of the Moon not in eclipse was too bright and over exposed. So I took a second image, exposed for the highlights.

  • 200 mm zoom

  • Aperture: f/4.8

  • Shutter speed: 1/20 second

  • ISO: 320

Here’s how I processed that RAW file.

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3. Blending the shots in Photoshop

After that, it was a reasonably simple job of blending the shots in Photoshop.

  • I opened the shadow exposed layer in Photoshop. The basic approach is to use layer masks to merge the layers.

  • On the highlight exposed layer, I selected and copied the Moon, and pasted it into the file with the shadow exposed layer.

  • The first thing I noticed was the wisp of cloud over the bright part of the Moon. That would make the blending slightly more difficult. So I used the Quick Selection Tool to select that bit of cloud. I copied it and pasted to a new layer, which I moved to the top of the three layers.

  • I opened a Layer Mask for the highlight layer in the middle. I then used a soft edge Brush Tool to paint black around the parts of the highlight layer I didn’t want to show. The cloud wisp layer above meant I was able to paint easily without worrying about painting over that.

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The science behind the eclipse

The eclipse occurs as the Moon passes into the shadow of the Earth. The first thing you would see is a slight darkening of the Moon as it heads into the penumbra shadow of the Earth (see below diagram).

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Then, as the Moon edges into the full shadow of the Earth (known as the umbra) you would begin to see a 'bite' being being taken out of the Moon, as the shadow of the Earth covers an increasing amount of our satellite.

Finally, the Moon passes entirely into the umbra and is not being lit any more directly by the Sun. It’s at this stage that you might think the Moon will disappear. In fact, it doesn’t. To the ancients, having watched the Moon being gobbled up, it might seem like the next stage is some form of grizzly aftermath of a celestial conflict, as the Moon turned blood red before their very eyes.

Why does the Moon go red?

So where does this eerie red light come from? It’s still sunlight, but this time refracted through the Earth's atmosphere. The effect is similar to that which gives us red skies at sunset and sunrise. As the Sun’s rays pass through more of the atmosphere at the start and end of the day, the blue light is scattered more and only the red wavelengths of light reach us.

Similarly, the light shining on the Earth is refracted by our atmosphere, bent around to our dark side, and then on to the Moon. And, once again, the blue light is scattered and the red light is the wavelength that is bent round and then sent on to the Moon.

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As the Moon slowly makes its way out of the umbra and into the penumbra again, at first you will see a sliver on the edge of the Moon brighten noticeably. Then the Moon will get brighter as it is increasingly lit partially by the direct light of the penumbra, and the red colour disappears.

Gradually, the shadow will grow ever smaller and eventually disappear, and our Moon will return to normal.