Photographing Stars

It’s ironic that while highly advanced telescopes are peering into deep space, most people in the industrialised world see less stars than ever before.  City lights and indoor lifestyles mean that some rarely see the beauty of the night’s sky.

When it comes to taking pictures of the stars, the Internet contains lots of excellent tutorials, produced by people far more experienced and qualified than me.  However, that can be a problem in itself, since they sometimes show results that are a bit too ambitious.  This post will show actual results that even a moderately able person can expect.

Settings

There’s no escaping the fact that you’ll need to review the manual for your camera, and find out how to change certain settings.  There are some suggested values, but the main thing is to know how to change them, and to experiment.

  • Shutter speed (or exposure time): how long the camera will record light for.  A couple of seconds seems to work best.  Although you might not be able to see it, the stars move across the sky and longer exposures will change the stars from dots to lines.
  • Aperture (or f-stop): how much light is allowed through.  Lower numbers mean lots of light gets through, so you want something as low as possible, for example 3.5.
  • ISO: how sensitive the camera is to light.  Some sites advise that you turn this up as high as possible, but a lower number can give cleaner results – as described below.  1600 seems to work OK.
  • Focus: the distance to the object that the camera is trying to focus on.  Possibly the most important setting that you need to make is to change the focus to be manual, and set it at infinity.  With automatic focus, lots of cameras won’t let you take a picture unless they can find something to focus on – which will leave you helplessly pressing the button with no effect.

Another thing that you might want to research is how to use the timer.  This will help you avoid shaking the camera when a picture is taken.  A tripod, or other type of camera stand, can also help you keep the camera steady.  However, it is possible to just prop the camera against something – particularly if you’re using the timer.

 

Environmental Conditions

Working out when to take pictures is also a key skill.  You obviously want clear skies, and your local weather forecast is a good starting point.  In the UK you can use the met office site, switch to the cloud cover option, and get some predictions.  However, your safest option is just to check the sky overhead before travelling out.  So long as you aren’t travelling too far, it should be similar.

You’ll find far more reliable predictions of the Moon’s phases.  Less moon means more stars, but be sure to bring a torch.  You can also find out information on local sunsets.  Who knew there were three twilights?  Click on the ‘More detailed’ link to see them all; and obviously the ‘astronomical twilight’ is when you’ll get the best pictures.

 

First Pictures

Now, what can you expect?  If you are living in a relatively urban area, with quite a lot of street lights, then you are not going to see a great deal.  Light pollution will mean that all but the brightest stars are going to be blocked out by light reflected in the atmosphere.  Still, your garden is the perfect place to make sure you know how to change all of the appropriate settings.

Example photograph of stars with light pollution.

Example photograph of stars with light pollution.

As mentioned above, quite a few tutorials recommend setting the ISO as high as possible.  However, you can get cleaner results by dropping the ISO and increasing the exposure length.  You can see a direct example of this in the two images below.  Cameras and conditions will vary, so you’re best bet is to take a number of pictures using different settings.

Left: ISO-6400 4sec; Right: ISO-1600 8sec

Left: ISO-6400 4sec exposure; Right: ISO-1600 8sec exposure

 

More Isolated Location

One of the main benefits of trying to take pictures of stars, is that you’ll eventually end-up somewhere that you can actually see them.  Google maps (or equivalent) can be very useful in trying to find nearby locations that are away from areas with light pollution, but easy enough to get to.  Some ideal locations are isolated car parks and lay-bys.  In the UK you can also see if you’re near a Dark Skies location.

It goes without saying that you should put your safety first.  If you’re travelling to an isolated location in the middle of the night, then it’s best to bring a friend, and tell somebody else where you’re going.  Any other cars might be there for things other than astronomy, but the less said about that the better.

What can you expect from one of these locations?  Generally, some more stars and a darker sky.

Example image from a less urban location.

Example image from a less urban location.

Photo Editing

As good as your pictures are, they can always be enhanced with photo editing software.

Image adjusted in PhotoShop

Image adjusted in Photoshop

In the example above, the original image on the left went through just two steps in Photoshop to reach the image on the right:

  1. Firstly, the original had a slightly red tint caused by light pollution.  There are tools to make fine adjustments, but in this case I just used the Auto Color option (Image menu > Auto Color).
  2. Adjusting ‘levels’ is the main tool that will enhance your photographs (Image menu > Adjustments > Levels).  The graph in the middle shows the light and dark shades in your photograph.  Move the left and right sliders to the edge of the graph, and probably move the middle slider over to the right a bit.  So long as the preview box is ticked you’ll soon work out what’s happening.

For GIMP you’ll find similar tools in the Colors menu.

Adjusting levels in Photoshop.

Adjusting levels in PhotoShop.

Spotting Constellations

Being ale to spot constellations can also be very useful, since astronomy sites and magazines often use them to point out other things of interest (e.g. planets).  I find that the easiest constellation to spot is the Plough (or Big Dipper), even though it isn’t a true constellation.

You can follow the line from two of the stars to find Polaris (the North Star), and from those you can work out two true constellations – Ursa Major and Ursa Minor.  This is probably no use if you’re in the Southern Hemisphere, where you are probably more familiar with the Seven Sisters; but it’s just about choosing one that you can find regularly, and using it to guide you to others.

Constellation animation

Constellation animation

 



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