Part 15 - The Night Sky - WildNatureNewZealand

The Night Sky

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  It’s been a fair while since my last article having been deep into another wee project which has taken up a lot of time over the last 8 months or so. Greig Caigou and I have put our heads together and come up with something that I think you will all enjoy so keep your eye out on the book shelves in early to mid October for something we think is pretty special.


  Having done a series of articles in NZHunter covering many different aspects of photography that can be applied to our hunting situations, over the next few issues I’d like to go into more detail on what it takes to capture specific images. Although I may have touched on some of these images briefly in the last series, this time I’ll try to explain things such as techniques, equipment and different ways to achieve specific results.


 

  Shooting For The Stars

  Photography deals with light so it’s kind of contradictory to talk about taking photographs at night. However, some spectacular images of landscapes and night skies may be achieved by using a couple of specialised pieces of equipment and manually selecting the correct exposure settings.


  There a few ingredients that you will need to produce night star images or ‘astro-landscapes’. Firstly, a fairly recent-generation digital camera because of the improved capabilities at high ISO settings they possess. Modern digital sensors are extremely sensitive to light and produce far less ‘noise’ and ‘grain’ than their predecessors while also giving good results with exposures that range from 30 seconds to many minutes.


  By far the most important ingredient in the astro-landscape recipe is a dark sky. Light pollution from towns and cities can be a problem with these types of images so ideally you’ll need to be as far away from them as possible. Naturally, our hunting trips provide ideal locations for perfect conditions.

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  A moon was out on the night this image was taken with a 20 second exposure at f/5.6 and ISO 800. The extra ambient light has given the impression of near daylight but also reduces the number and brightness of stars captured. One plus is that some nice reflections are visible in the shot.


  The long exposures required for these images will need a good quality, sturdy tripod to mount the camera on. Windless nights are also a prerequisite as any slight movement or knock of the set up will result in blurred shots. As with daylight landscape images, a wide angle lens is the preferred option to capture as much of the sky as we can and a lens in the 17mm to 35mm range is ideal. If your choice of camera is a compact digital with a fixed lens then simply zoom right back as wide as the camera will allow. We need to drag in as much light as possible so lenses with wide apertures are better.


  One last piece of equipment you will need is a cable or remote shutter release. There are many available at relatively low prices but features will vary. The minimum required feature is the ability to lock the shutter open for a specific time.


  So, once you’re out of town, in the dark and have the right gear, the next step is critical. You're using a lens nearly wide-open, so focus must be dead-on due to the small depth of field. The best way to achieve good, sharp focus is to use the ‘live view’ mode on the camera’s LCD screen. Find a bright star or planet and zoom the live view into 5x or 10x and using the manual focusing ring, bring the fuzzy star into a pin point of light. At 10x magnification it can be a bit of a chore trying to find the star on the screen but persevere and it’ll become easier. Once focus has been achieved you can recompose the shot for good composition to include some foreground interest such as a tent or hut or perhaps just some interesting rocks or trees.

  Exposure

  Now its time to set the exposure. Always use ‘manual mode’ so you have complete control over exposure. Shutter time should not be any longer than 30 seconds as any more and the earth’s rotation will render the stars as streaks rather than dots or spots. (I’ll deal with star trail images a bit later). If you do need slightly longer shutter times, then set the camera to ‘bulb mode’. The aperture needs to be set at wide open or just back from wide open. Most lenses are not at their best opened right up so if you have the luxury of an f/1.4 lens, back it off to say f/2. If your lens is not that fast (say an f/2.8 or f/4) then you will have to settle for wide open. The final exposure setting is ISO. Here you will probably need to experiment a little depending on your camera and lens combo. Try ISO set at 1600 to begin with. You will capture more information with higher ISO but at the expense of more noise. As I say, experiment with different ISO’s to achieve the most pleasing result.


  The exposure for the opening image to this article was 20 seconds @ f/2.8, ISO 200. Faint moonlight which was also ‘bouncing off’ the distant snow meant a faster shutter speed of 20 seconds and a lower ISO was able to be used for an effective result.

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  Not a terribly interesting foreground but correct exposure has captured the stars and milky-way well.

  ( 30 seconds @ f/2.8, ISO 1600 )



  To obtain foregrounds with more detail and interest than a simple silhouette, try lighting the foreground with a flashlight or headlamp for several seconds of the 30 second exposure.

  Star Trails

  To create these stunning star trail images, much of what is written above for ‘static’ night sky shots apply. Same sturdy tripod, same dark sky conditions, same focusing technique and camera equipment. The major difference between the two shots is that of exposure times. With the static star images we were using exposure times of no more than 30 seconds whereas to produce ‘trails’ of stars we need either a much longer single exposure or a series of up to 100 shorter 30 second frames.


  The first technique will again require the use of manual mode. The Earth rotates 360 degrees every 24 hours. To create a star trail that goes 90 degrees (a quarter of a circle in the sky), you want a shutter speed of six hours. However, most photographers keep the maximum length of any individual trail to about 15 degrees, which means an exposure of about one hour. Once focus of the stars and good composition is achieved, use your remote release with camera in ‘bulb’ mode to set the desired exposure. Depending on your camera, one hour may be too long for a clean image so experiment with ISO to see how your camera copes.

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  The above North Canterbury shot is a single exposure of 862 seconds (just under 15 minutes). A longer exposure of say 30 minutes would produce trails twice as long. The well lit foreground is a result of dim lighting reaching out from the shearer’s quarters some distance behind the camera.

  A far better method which produces more pleasing and cleaner images is to take a series of shorter exposures and combining them on the computer later using a dedicated star trail programme such as “Startrails”. This free download can be found at this address –


  http://www.startrails.de/html/software.html


This programme is fairly straight forward and easy to use with the ability to also turn the frames into a nice, moving time lapse sequence.


  So, using the static star image exposure of 30 seconds as a starting point, take a series of shots experimenting with different settings to obtain a good clean image with nice bright stars. Once you’re happy with the shot it is a simple case of repeating that image 50 to 100 times more. The more frames you include, the longer the trails will be. This is where your remote release makes things so much easier. Depending on the model, you will be able to programme the release to take say 50, 30 second shots consecutively. Below is a photograph showing the one I use. From left to right the settings signify the following –


  Delay = Time delay before the first shot is triggered (the highlight bar in this case signifying the ‘delay’ setting which has been set at 1 minute)

  Long = How long the shutter will stay open for each shot

   Intvl = Time between each shot (usually only needs to be a couple of seconds. Much more and you will end up with gaps in the trails)

  N (figure in brackets) = number of individual frames that will be taken (50 in this example).

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  The beauty of a release with these programmable functions is that you can set it and walk away. Go back into the hut and have a brew. If your remote release does not have the ability to programme consecutive frames you could achieve the same number of shots by manually opening the shutter for 30 seconds, 50 times. Fairly laborious and monotonous but if that’s all you have then that’s the way it has to be.


  If you would like more light and detail in the foreground you can again use the headlamp to shine over the area for one of the fifty frames.


  You may have seen some really impressive star trail images where the stars rotate around a single point in the sky. This is no fluke and can be achieved quite intentionally by pointing the camera at just the right angle and direction. The Earth rotates around the north and south poles, so all star trails are centered above them. In our southern hemisphere this rotational point is around the South Star, Sigma Octantis. The easy way to locate this point in the sky is to have the camera pointing directly south and at a 41 degree angle. (Marlborough is at 41 degrees south whereas the bottom of the South Island is at 45 degrees south although a few degrees out will not make a heck of a lot of difference). I’ve also discovered that it is just as important to have a wide enough angle lens to be able to incorporate this point in the shot and also maintain the foreground in the frame.

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  An Awatere valley image of 50, 30 second frames combined in “Startrails”. As can be seen, I didn’t have the camera at the optimal 41 degree angle to place the centre of rotation better in the frame.




  Hopefully all this doesn’t seem too daunting. I’ve only just started experimenting with these types of images myself but I can see the potential for some really outstanding results once I get things ‘narrowed down’ and become more familiar with how my set up copes with these settings and exposure times. Like most other aspects of photography I urge you to experiment a lot, get to know what your gear can handle to produce the best results.


  ps – if there is any specific type of image that you would like to know more about, just drop Greg a line or contact me direct through my website –


  I’ll do my best to ‘shed some light’ on your enquiry.



  Good shooting,  

   Matt


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