Capturing the stars: Night Sky Photography

by James Rushforth Oct/2014
This article has been read 16,928 times

From a personal point of view, photographing the night sky is one of the most difficult, frustrating yet ultimately rewarding aspects of photography. It requires perseverance and ultimately commitment, not least because any sane person would be in bed at 2am, rather than scrambling around in the dark with a load of camera kit. Here are a few tips to get you started on capturing the stars… 

What you will need:

  • A camera with as large a sensor as possible
  • Tripod
  • Remote release cable (only for star trails)
  • Headtorch
  • Warm clothing
  • A lot of time

Nuvolau and the Tofanas by night  , 218 kb

Nuvolau and the Tofanas by night - Single photo, 22mm, F3.2, 12mins, ISO100. Taken with a bright moon that was actually casting shadows. The orange glow is not sunset (the shot was taken well after dark), it is light from the nearby town of Cortina.  

  1. Choose the right night - There's little point in heading out to photo the night sky if it's cloudy, so find and check a decent weather forecast beforehand. If it’s particularly the stars and milky way you're after, choose a night with a small or ideally new moon. There are many lunar cycle phone apps that can be downloaded for free. 
  2. Location - Obviously you're looking for somewhere with some good scenic possibilities, however ideally this needs to be as far away as possible from any obvious light pollution.
  3. Compose the photo - Before heading out into the dark it is important to have a good idea of what you're going to photo. Ideally if you have the time and the patience it's worthwhile composing the shot before full dark. However be prepared to improvise a bit depending on the location of the stars / moon (more on this later).  
  4. Focus to infinity - Night shots look best with the stars properly in focus. Learn where the infinity focus of your lens is (this varies between lenses and rarely exactly corresponds with the infinity symbol exactly, even on expensive lenses). If there is a moon or bright light in the distance you can use it to auto focus. Some people auto focus to infinity during the day and then tape their focus ring  to stop it moving - a bit overkill but it works (just be sure to flick the lens to manual focus after).
  5. Static stars or star trails - This is the big decision you need to make when photographing the night sky. Because of the Earth’s rotation, you only have a finite amount of time to expose the photo before the stars appear to 'move'. Thus a fairly short exposure is required for static stars whilst a longer exposure will produce star trails as the Earth rotates. The two require contrasting techniques which will be described in more detail below. 

The milky way hangs above the Ogwen Valley, 227 kb

The milky way hangs above the Ogwen Valley - Single photo, 14mm, F2.8, 30secs, ISO1250. Taken late at night (1am) with a small moon so the stars were brighter. A relatively short exposure to 'freeze' the stars, creating a 'star field'.

Moonlight on the Passo Giau, 224 kb

Moonlight on the Passo Giau - Single photo, 16mm, F5.6, 17mins, ISO100. Taken with strong moonlight over the right shoulder with Polaris clearly in the shot. A long exposure allows the stars to trail.  

 

Static stars / star field

This is arguably the harder of the two techniques and is unfortunately more gear / equipment (read money) dependent. 

Composition
Static stars generally look best if you can get the milky way in the frame. Unless you're very much into astronomy you won't know where this will be (it moves) until it's full dark and you can recompose your shot. 

Your camera will pick up more light than the naked eye but you should still be able to make out the line of the milky way which is usually brighter higher in the sky.

Camera settings (EXIF)
Focal length - Because of the Earth’s rotation you only get a finite amount of time before the stars move, making them blur and look out of focus. 

(You can get mounts that track the sky, allowing longer exposures, but this obviously compromises your foreground.)

The amount of time it takes before the stars move is dependant on the focal length of your lens. The wider the lens the less the stars appear to move, allowing a longer exposure. Some time ago photographers developed the ‘600 rule’ for working out exposure times in correspondence with varying focal lengths. The straightforward formula divides 600 by the focal length in mm. For example a 50mm lens mounted on a full frame camera would get you a 12 second exposure window (600 / 50 = 12). Personally, due to the resolution of modern cameras and the personal need to print large, I use a ‘450’ rule which has been adopted by many photographers. 

The following table provides rough exposure times for varying focal lengths using the ‘450 rule’. Obviously it should be used as a rough guide and can be experimented with at leisure.

450 rule table, 101 kb

A night time pilgrimage over Longridge Fell , 225 kb

A night time pilgrimage over Longridge Fell - 4 photo stitch, 14mm, F2.8, 30 seconds, ISO800. The light trail was achieved with a blue LED hand-held torch.   

Exposure - You’re aiming for the maximum possible exposure time before the stars move and blur (see table above).

Aperture - Because you only get a relatively short exposure (see above) you generally want the lens 'wide open' with the lowest possible aperture. The only exception is on some pro setups where stopping down from wide open can improve corner sharpness (for most people this isn't an option however as you need all the light you can get). 

ISO - As with nearly all photography you're aiming for the lowest possible ISO to prevent the image from looking grainy. How low you can get the ISO depends on the speed of your lens, focal length and light conditions at the time of shooting. 

Example settings - The camera settings will change nearly every time you're out depending on the light conditions. However here are two rough examples:

Full frame body - 24-105mm F4 lens. Using a focal length of 24mm on a full frame would give you a maximum exposure of 19 seconds. You’d want the lens wide open at F4. This would require an ISO of roughly 6400.   

Full frame body - 14mm F2.8 prime lens . Using a focal length of 14mm would allow a 32 second exposure. With the lens wide open at 2.8 you can get away with an ISO as low as 800.

Tip - If you're serious about getting into night photography the Samyang 14mm F2.8 is a superb lens for the price and an excellent starting point.

The Milky Way over the Gran Vernel, 229 kb

The Milky Way over the Gran Vernel - 10 photo stitch, 14mm, F2.8, 30 seconds, ISO500.

The Tre Cime di Lavaredo bathed in moonlight, 227 kb

The Tre Cime di Lavaredo bathed in moonlight - Single shot, 14mm, F2.8, 30 seconds, ISO3200.

Tarn Hows panorama, 220 kb

Tarn Hows panorama - 4 photo stitch, 14mm, F2.8, 30 seconds, ISO800.

 

Star trails

Star trails are arguably easier to accomplish as you get a much longer exposure window making it easier to keep the ISO down. 

Composition
Star trails normally look most effective if you can get the North Star (Polaris) in the shot. This is because the North Star lies in an almost direct line with the North Pole and the axis of the Earth’s rotation. Thus Polaris remains almost motionless in the sky whilst all the stars of the Northern sky appear to rotate around it. 

The North Star is in fact the 50th brightest in the sky and is most readily found by first locating the easily identified Plough (big dipper) asterism of the Ursa Major (great bear) consolation. The righthand two stars of the ‘saucepan / plough‘ then point almost directly at the North Star.

Patrick Deacon and Lynne Hempton climbing Via Normale on Torre Quarta, 233 kb

Patrick Deacon and Lynne Hempton climbing Via Normale on Torre Quarta - Single shot, 17mm, F5.6, 40 mins, ISO100.

 

There are two ways of creating star trails:

Star trail method 1) A single long exposure

This is my preferred method as I personally think it has a 'purer' feel. Obviously you can't see star trails with the naked eye in the first place; however the photo you are taking is an exact and fair representation of what’s happening over said period of time. 

A long exposure also allows a lower ISO resulting in a less grainy foreground. 

Camera settings (EXIF)
Focal length - As above, the more you're zoomed in, the faster the stars will appear to move. In the case of star trails a large focal length is not a problem, as it’s the movement you want to capture.  

Exposure - How long an exposure you decide on will depend on your chosen focal length and how big you want the trails to be. 

As a rough example on a full frame at 14mm I tend to go for about 40 minutes. At 200mm I tend to do about 15 minutes. 

To get an exposure over 30 seconds on most cameras you will need to use 'bulb' mode in conjunction with a remote release switch to keep the shutter open (holding the shutter button manually for 40 minutes gets tedious!)

Aperture - Generally you want a fairly wide aperture (low F number) to get lots of light in and ensure the stars are bright. However with such long exposure times (see above) you can afford to stop it down slightly to improve corner sharpness. 

ISO - Again you're looking to get the ISO as low as possible to reduce noise in the dark areas. For a 40 minute exposure you may well be able to get the ISO down to 100. If it's a particularly dark night however you may well lose the foreground. 

Example settings - It's much harder to give example settings for long exposure star trails as there's a huge variety of set ups depending on what you want to achieve and the amount of light at the time. Ultimately you will need to experiment.

Ogwen Valley startrails, 230 kb

Ogwen Valley startrails - Single shot, 14mm, F3.2, 35mins, ISO100. 

Star trail method 2) Use 'stacking' software

This involves taking a series of photos, usually at 30 second intervals for a minimum period of roughly 30 minutes. You then stack the photos to create a star trail. This is most commonly (and arguably best) done in Adobe Photoshop, but there are many different software possibilities:

Imagestacker  
StarStaX 
StarTrails 

There are numerous possible ways of doing this but the easiest is to dial in a 30 second exposure (lens wide open with an ISO between 800 and 3200), put your camera into continuous shooting mode and then hold the shutter open with a remote release and let it take photos for x amount of time.

The longer you let it take photos for, the longer the star trails will appear to be. There are too many possible software options to provide a detailed walkthrough but all of the software listed above comes with instructions.  

 

Some departing tips to save you time:

  • Learn where your infinity focus lies for each lens.
  • Come up with a suitable composition in daylight.If you need to do it at night use the highest ISO you can.
  • Test your head torch before setting out. Make sure your camera battery is charged. 
  • Learn to operate your camera in the dark without a head torch.
  • Find a friend - night photography is a lonely business. If you can't persuade anyone to join you, take an audio book. 
  • Use a decent tripod.
  • Learn to find the North Star.
  • Find a dark spot away from light pollution. 
  • Find a good weather forecast.
  • Get a sunrise / sunset app as well as a lunar cycle app.
  • Tell someone where you're going and roughly what time you'll be back. 
  • Pack lots of warm clothing. 
  • If you use long exposure noise reduction remember to turn it off if you do a 40 minute star trail. 
  • Make sure you know how to get home in the dark. 

 

Some advanced tips:

  • Experiment with stitching static stars, remembering that the galactic core is often located straight up.
  • Have a look into post processing methods to reduce noise. 
  • Look into 'mirror up' and 'long exposure noise reduction' for shorter exposures. 
  • Experiment with a decent flash and some coloured gels for some interesting foreground effects. 
  • Consider two different focus points for well-lit foregrounds.

 

Have fun and happy star gazing! 

Night falls over the lake of Tarn Hows, 221 kb

Night falls over the lake of Tarn Hows - Single shot, 14mm, F2.8, 30 secs, ISO2000. 

 

 

James Rushforth, 90 kb
 James Rushforth

James is passionate about the Dolomites and has lived there for the last few years. He recently authored the Rockfax guidebook Dolomites : Rock Climbs and Via Ferrata which featured many of his amazing photographs. He is now working on a new book for Rockfax to Finale, also in Italy.

James Rushforth is a professional photographer and you can see his portfolio on Smugmug, and follow him at JamesRushforth.com

 

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