Photographing the Night Sky

Something appeals to me about photographing the night sky. I am not exactly sure what it is, but it probably has something to do with being able to create something the casual viewer will never see. While I love pictures taken with telescopes of far off nebulas and galaxies, I do not have the equipment or late night patience to make that happen.

Copyright © 2008 Russ Beinder. All rights reserved.
Nikon D700 30s, f/2.8,  ISO3200, 50mm. My camera was rested on the ground, focusing was manual (several attempts), and the shutter was triggered by directly pressing the shutter release.

Equipment

Wide field photography can be done with fairly basic equipment; you will need a  camera with a time exposure feature and a method to keep the camera steady at a minimum. As the name implies, wide field images show off a large section of sky at one time. This gives many compositional possibilities for terrestrial additions to your image.

Many digital point-and-shoot cameras can open the shutter for up to 15 seconds. With the lens zoomed out as far as possible, many will have an aperture of f/3.5 or bigger (smaller number). This is sufficient to make a photograph of the night sky. You will probably need to set the ISO to 3200, but trial and error is your friend here. You can take a fair number of 15 second shots to find what works best. Noise will certainly be a problem with less expensive cameras, but can be hard to see the difference between noise and star, so no one may notice.

Copyright © 2008 Russ Beinder. All rights reserved.
Nikon FA 3600s, f/1.4, ISO100, 50mm. Fuji E6 film.

A digital SLR camera will give you more flexibility. They will usually have a BULB option for extended exposures and the possibility of adding a remote shutter release. Some will also have an interval timer. If you do not have a remote shutter release you can use the self timer to trigger the shutter without touching the camera.

A camera with a BULB setting will be a must if you are shooting with film as will a cable release with a lock as you will not likely have ISO 3200 film (nor do you want it). If you have an ISO 100 film you will need more that 15 seconds. Since you will record about 1/6 of light as the digital ISO 3200 you will need about 480 seconds of exposure to capture the same amount of light. Check your film specifications for reciprocity failure. That will tell you what will happen to the colour balance and exposure time. You may need to add more exposure to compensate.

Everything is Spinning

It may not be obvious everyday, but the earth is turning on its axis. We are in constant motion relative to the stars. This means one of two things to the night photographer: the stars will seem to speed across the sky or you will need a tracking mount so your camera keeps up with the stars. I do not have the latter, but there is a side effect to this approach. If your camera is spinning with the stars you have no chance to include an interesting foreground.

There is one really important fact to know about the spinning; there is a point in the sky that appears to be the center of the circle: Polaris for the northern hemisphere and Sigma Octantis in the south. It is important because if you know where the center is you can compose your shot according to the hidden arc of the stars.

Combination of 204 discrete exposures. Nikon D700 30s, f/2.8, ISO1000, 14-24mm.

There is Too Much Light

Whether it is light pollution, the moon, or the dawn, too much light is not your friend. Your nice black sky will be completely washed out by light sources other than the stars. You do need enough light to expose any foreground you many have, but anything beyond that is too much. Digital cameras offer a solution that film never could. Many digital images of stars can be combined into a single image using a tool such as Photoshop or Startrails. The trick is to find an exposure that will keep the background dark with some brightness in the stars. You can add a separate exposure for the foreground.

I walked in a large circle with a small flashlight. The light is broad as I moved away from the camera and narrow as I walked towards it. I waved the flashlight up and down some of the cacti to fully illuminate them. Nikon D700 30s, f/2.8, ISO1000, 14-24mm.

If you control it, extra light can play a part in the terrestrial portion of your image. A flash, a flash light, or just about any light source can play a part. You can light up a very large area with a single light source as you can move the light while your shutter is open.

Copyright © 2008 Russ Beinder. All rights reserved.
Passing car headlights provided the lighting for this old dead tree.

Final Notes

Stars are not the only thing that lights the night sky. If you live in an area with northern lights they can make a spectacular subject. Remember that they are constantly moving; you will need to use a fairly fast shutter speed to unless you want a smoother look.

Copyright © 2007 Russ Beinder. All rights reserved.

The moon can also be a good subject. Like the stars it is also on the move. The good news is that it is very bright. An exposure of 1/250 of a second, f/5.6, and ISO 200 is all you need.

Copyright © 2007 Russ Beinder. All rights reserved.
Venus and the moon in close proximity.

If you want to have a clear image of the moon in a shot with other night elements you will likely need to combine multiple exposures as the brightness is so different.

This image is a composite. The moon is exactly where it appeared as the sun went down, but it was exposed for a much shorter time than the rest of the image to ensure it had definition.

One warning about digital cameras over film is that the image sensor will get increasingly hot as it is energized. This means that the longer the exposure you make, the hotter it will get. The hotter it gets, the more noise that gets introduced.