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Why Your Tripod Is Never Stationary

by Alyn Wallace Juli 15 2018
 

What if I told you that no matter how good your tripod is, or how much money you may have splashed out on it, it is never truly stable? Place it on the most solid of concrete floors and hang your bag from it, there’s nothing you can do. What am I getting at here? Well, I’m not talking about little shakes from wind or other tiny vibrations. In fact, it’s quite the other end of the scale.

Milky Way and Zodiacal Light in the Elan Valley, Mid Wales

(22x image panorama | f/2.8 | 25secs| ISO6400)

Earth is constantly spinning on its axis, one revolution every 24 hours giving us our days. For daytime landscape shooters, it’s a motion that causes no concern but in my line of photography, capturing distant stars and galaxies, it's one of our biggest hindrances.

I’m constantly seeking the perfect darkness in landscapes free of light pollution and given this lack of light, long exposures are essential. Not to mention the fact that light collected from stars and galaxies has travelled for millions of years over unfathomable distances. Ideally, I’d like to keep my shutter open as long as it takes to collect enough light for a bright and clean exposure, but sadly the rotation of Earth causes my tripod to move relative to the stars and thus they begin to trail in the image.

In an attempt to keep the stars round and pinpoint, as they appear to the naked eye, a maximum shutter speed exists which is directly related to the focal length of your lens. A simple formula known as the ‘500 Rule’ helps to find an estimate of this limit.

For example, my most used lens is the Samyang 24mm f/1.4, so dividing 500 by 24 gives my maximum shutter speed before the stars trail which is roughly 20 seconds. In such dark environments, this is incredibly limiting and forces me to use ISO values of 6400 and sometimes 12800! (Oh and 500 only works for full-frame cameras, if you’re shooting with a crop sensor it becomes the 300 Rule and 250 for micro four-thirds).

Of course, this motion of Earth could instead be used to artistic effect to create star trail images very reminiscent of Vincent van Gogh’s ‘Starry Night’. Leaving your shutter open for hours on end isn’t advised though as it puts your sensor at risk of overheating and damage. It’s best to take multiple shorter exposures like 30 seconds or a couple of minutes and to later stack these exposures in order to reveal the motion of the stars over the course of multiple hours.

Star Trails in the Brecon Beacons

(1000+ images stacked | f/2.8 | 30secs | ISO1600 | 7 hours total exposure)

When facing north in the Northern Hemisphere, the stars form huge circles in the sky. Right at the centre of those concentric circles is Polaris, the North Star. As Earth’s axis of rotation points nearly directly at Polaris, it remains in the same position in the sky, hence why it was always used as a navigational guide when our ancestors crossed the seven seas and open plains.

You can counteract Earth’s rotation by utilising a star tracking mount. There are many out there on the market such as the iOptron Sky Tracker Pro and the Skywatcher Star Adventurer and Mini. These mounts are set up by aligning their axis of rotation with Polaris (in other words, parallel to Earth’s axis of rotation) and then rotating your camera in the opposite direction to Earth’s rotation and at the exact same speed. This keeps the stars fixed within your frame and ‘tracks’ them, allowing you to take much longer exposures of the stars without having any trailing. Collecting more light in this fashion will reveal a lot more detail from fainter objects like the Milky Way.

Now, not only is Earth rotating on its axis but it also orbits the Sun, giving us our years. The motion of the planets are easily predicted using Kepler’s laws of motion so if you wanted to know where Mars will be on January 2nd 2084, it’s no difficult feat. And in the world that has an app for everything, it’s easier than ever! Stellarium is my favourite night sky emulator, it allows you to see where the constellations, planets, Milky Way and more will be at any given date or time in the past or present from any location around the globe.

It is the predictability of Earth’s motion and the celestial bodies that give rise to my addiction to this genre of photography.

The moon rising underneath the Milky Way. Mars, Saturn and Jupiter also line the beautiful night sky of the Spanish Canary Island, La Palma

(18x image panorama | f/2.8 | 20secs | ISO3200)

It allows me to plan my shots very much in advance, pre-visualising a scene before capturing it in reality. If I find an interesting composition whilst out on a stroll one day, my mind will instantly begin to work out what wonders of the night sky I can one day compose into the scene. A classic example of this is when stumbling across a nice south facing composition - I know that I can return one day and photograph the galactic core of the Milky Way there (weather and light pollution permitting of course!).

The rush of capturing something I saw in my head weeks, months, sometimes years in advance to actually pressing the shutter button is highly addictive. And with each failed attempt and extra day waited, the reward only becomes greater. If I don’t get that Milky Way shot during the month-long window that year, I can go back the same time next year. Not only does the longer wait induce a bigger reward, but, I’ll be returning with hopefully a new skill set and a more mature eye.

The predictability of the night sky makes it easy to line things up, I suppose it's the most long-range form of composition there is. And as much as I love aligning things and capturing images that depict our place in the universe, I have recently sought to capture the interaction between astronomical events and the land on which we live.

Take this image, for example, moonlit curtains illuminating the front of Sgwd Ddwli in the Brecon Beacons. In this instance, it wasn’t about photographing the celestial body, the Moon, but more the interaction of the Moon’s light with the landscape we are so familiar with.

Moonlit Curtains in front of Sgwd Ddwli, Brecon Beacons

(Single exposure | f/4 | 20 secs | ISO3200)

It took a few attempts to capture this. After the initial scouting and planning the angles required the first attempt failed; my predictions were completely off. The second attempt failed because there were too many leaves on the trees blocking the light. Then finally everything came into place; it was the onset of winter and we had just had a good lashing of rain, the leaves had all fallen and a couple of days before full moon gave a window of clear skies at just the right time. Oh, that adrenaline! It was such a surreal moment and far more beautiful to witness than anything I had pre-visualised. What made this one even more special was my lack of certainty over whether it was even possible or not.

Another such image is this one titled ‘Portal’ which I took at Durdle Door back in 2016 (honestly I’m still in shock I came back from that place with a unique image!). It captures the last light of the setting moon spilling through the gap in Durdle Door as the night sky began to darken and give way to fainter objects like the Milky Way. It was such a short-lived and ethereal moment and it’s a capture that has remained one of my all-time favourites. After first photographing the scene without my silhouette I knew immediately that I had to jump in for a selfie so that I could depict that feeling of going through a portal and into space as the moonlight fades and the night sky comes to life.

Moonlight spilling through Durdle Door, Dorset

(2 shot HDR | f/2.8 | 10 secs and 20 secs | ISO1600)

Astrophotography must be the only form of photography that becomes better with an absence of light. Capturing the hidden beauty of darkness through long exposures uncovers a whole new world not readily available to the naked eye but the more time I spend capturing it, the more I begin to see it. My imagination spills onto the black and white canvas in front of me as I hunt out the most otherworldly landscapes to continue my work.

The other-worldly landscape of Cappadocia, Turkey

(7x image panorama | f/2.8 | 25secs| ISO6400)



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