The night sky is not just a black background festooned with stars. It is more complex and interesting than that. There are clouds of interstellar gas that stretch from horizon to horizon in what we call the “Milky way”. We are in an outer spiral arm of this immense galaxy. We are looking at our own galaxy from the inside. The gas clouds are most prominent towards the centre of our galaxy and can be luminescent or dark. In addition there are a couple of sister galaxies, the large and small Magellanic cloud that can be seen clearly with the naked eye.
I am interested in the different colours of stars. Some of the colour is because of the different gasses that make up the star (Red giants and blue dwarfs) some of the colour is altered by the dopler effect as stars move toward (blue shift) or away from us (red shift).
In the city we don’t see much because of atmospheric dust and pollution and the bright lights that shine all night (light pollution). However a trip to the country at night is a great opportunity to observe the night sky. Taking a camera and pointing it at the sky can however be disappointing. How do you capture the night sky?
Here are my tips.
- Focus at infinity and then switch to manual focus. You don’t want the camera hunting for focus in the dark night sky. You may set the focus on distant city lights or on the moon.
- Use a wide angle lens. This gives the best field of stars.
- Use a tripod. You can trigger remotely or use delayed shutter release.
- Use manual exposure settings. For an image with distinct stars set the shutter speed to around 30 seconds. Open the shutter as wide as possible. Turn off Auto ISO settings and set the ISO manually. Start at ISO 400.
- Increase your ISO until you can clearly see the gas clouds in the centre of the Milky way. You may need to go up to 1600 ISO. You may not be able to see the gas clouds with your naked eye, but the camera will see them.
- Unless you are prepared to wait ages for images to process, turn off “long exposure noise reduction”.
Here is an example of how many stars you will see as you increase the ISO.
Once you have a good exposure you can move your tripod around and with the same settings reframe your picture to include an interesting foreground.
Postprocessing can then bring the star fields into sharper focus. In this instance I used NIK tone mapping along with contrast enhancement and sharpening.
Once you have captured the field of stars you can try and capture star trails. Simply turn the ISO back to 200 or 100 and increase the shutter time to 20 minutes. I have found that 2 hours gives an excellent star trail, however the glass of the lens will cool down and can fog over in that time. The battery may go flat. Also there will be a lot of digital noise. Setting the time to 20 minutes, then combing the images in photoshop will give a cleaner result.
Here is a single 5 minute exposure.
This image was made by stacking 30 to 40 sixty second exposures in ZM combine software. I don’t like the lumpy look of the lines and have decided 20 minutes is a better exposure.
I haven’t produced my ideal star trail photo yet. This is a work in progress. I hope that you have learned from my experiences to date and best of luck in producing your own star photos.
30 minute exposure using star trail setting in the menu of Nikon Coolpix