The sky at night is a magnificent place, no more so than when out in the countryside on a clear night. Much of the United Kingdom suffers from light pollution to a varying degree, but you don’t have to go far for the sky to clear significantly of this pollution – and then the myriad of stars become much easier to see once the eye has adjusted. The sky is incredibly active at night – look up and you will see satellites faintly illuminated moving around in orbit and if the orbit is right the International Space Station is visible and incredibly bright as it streaks above the Earth with it’s crew of astronauts. At certain times of year meteor showers are very active, this year the Perseids were incredible in August – even if the camera missed them.
I enjoy taking pictures of the night sky, although living in Milton Keynes the opportunities are a little bit more restricted because of the light pollution from the street lamps and other sources. It doesn’t stop you from viewing the sky, but move out into the countryside away from the cities and you’ll be amazed just how many more stars become visible. Having been in the depths of Suffolk at Elveden Forest last week the opportunity arose to point the camera skyward and try and get an epic star trail shot from within the forest. The result was probably my best yet.
What are star trails you ask? I’m no astronomer so the explanation will be somewhat simple, but the sky isn’t still basically because of the Earth’s rotation on its axis, and all the stars will appear to move around the celestial pole – which in the northern hemisphere is very close to the star Polaris. Using long exposure photography or taking many continuous shots of the sky will allow you to build a star trail photograph.
This short video shows the skies above our lodge moving over an almost 4hr period on Thursday evening. The sky was mostly clear but you see high clouds whisking through with an orange tint from the light pollution. The video is probably best viewed full-screen as the compression affects the stars somewhat. I used the individual images recorded for the star trail shot for the time-lapse video – 433 images shown in just 30 seconds, with the obligatory music obviously…!
So what do you need to shoot a successful star trail? A sky free of clouds and light pollution is a good place to start obviously. A sky without the moon is also useful as the moon is tremendously bright and will wash out stars and the final image. I also like to have some form of foreground interest – a windmill, a telescope, a derelict stately home perhaps – so the image isn’t just stars. In terms of camera gear I use my Nikon D600 on a sturdy Manfrotto tripod. In Elveden I used my 24-70mm f/2.8 lens as it was the widest lens I had with me, but if you have wider then great. Attached to the camera was my cable release, and that was it. The other essential ingredient is a lot of patience…!
I set the camera up in daylight to ensure the focus and framing was OK for the trees, then left the tripod outside and returned after dark. With the camera in full manual mode, I experimented to get the correct exposure settings for a little while, the idea is to get as high an ISO and as wide an aperture as possible in a 30sec exposure. I eventually settled on ISO 800 and f/5.6, I could probably have dropped the f/ a little bit more in hindsight. It’s all a trade-off between noise and the number of stars the camera records, try just one shot and you’ll be amazed how much more the camera sees from what you can with the naked eye. Once happy with the settings I covered the viewfinder (prevents light leaking onto the sensor as the long exposure records), set the camera to Continuous High-Speed shooting, and pressed and locked the cable release trigger. And off the camera goes.
Well I say off it goes but there is a “gotcha” to all this…if you are a Nikon user the continuous shooting mode cuts off at 100 shots. Hence why I set an alarm for 45-50mins and go out and reset the camera after that time. Simple enough to do, just unclick the cable release, wait for the shutter to drop, then reclick the cable release. A tad annoying though. Some Nikon cameras (mine included I think) have built in intervalometers these days which may allow you to take more than 100 shots, but I haven’t experimented with this.
When all was said and done I ended up with 433 star trail images. Above is a “before” and after split of how I edited them all up – it takes a bit of experimentation to get the settings right and a lot of it is purely down to personal preference. I shot all the images for this star trail in JPEG format, but I may have had more control on the editing had I stuck with RAW format – I had thought it would save space on the card, but in hindsight I doubt it would make much difference.
Almost 4hrs of celestial activity above Elveden Forest. Wow.
So, what edits did I make in the end? I adjusted the white balance (reduced it slightly to make the sky less yellow/orange), nudged the contrast up a bit and desaturated the image slightly. By increasing the contrast I lost some of the fainter stars that were recorded on the unedited image, but it helped to make the final image better in my opinion. I then applied these settings to all 433 images and exported them from Aperture into a folder on the desktop.
That then leaves me with lots of images to combine into just the one.There are several ways of doing this – you can use Photoshop to stack the images, or one of a number of different free applications to do the same trick. There is a free app for the PC called “startrails.de”. and I use a free app on the Mac called StarStax, and it really is that simple – load the images in, select “Lighten” mode and let it work some magic. Job done, one star trail created.
You will notice that the foreground interest is much clearer on the finished product than on the individual image. This is due to the fact that I have stacked 433 images on top of each other using the Lighten blend method, so the finished image will be clearer definition. The stars are always moving so won’t get significantly brighter, but it helps the foreground for sure.
The final steps I took on this image were to turn the image black and white and to place a border on it. Why monochrome? It’s a matter of taste really, but I find that 9 times out of 10 the image looks better that way. Believe it or not but the stars are all slightly different colours – some are more blue, some are yellow, some are pure white. On a star trail with as many stars I caught in Elveden it all tends to end up a bit of a mish-mash, so monochrome neatens it up.
So that’s a star trail in a nutshell. It is a lot of work for a single image, but can make for a very interesting image and a completely different view of the sky and stars we may just take for granted gazing skyward at night sometimes.
Click on either image to go to my Astronomy gallery and see the images full-size, including some other star trails.