Night sky photography tips and tricks

Night photography, or astrophotography, is easier than you may think. It really boils down to a little planning and knowing a thing or two about how a camera works. 

• Auroras expected to dazzle again tonight

Here is a simple guide to capturing shots of the night sky, and some simple tips and tricks that will open up a whole universe of potential for anyone with a camera and a tolerance for late nights under the stars.

The basics

While a camera with manual controls, a fast wide lens, RAW capabilities and a big sensor does make a big difference, stunning night sky shots of meteors, the Milky Way, the northern lights and star trails can be captured using just about any camera these days.

Equipment aside, here is what you, the aspiring star shooter, need to know.

Night sky shots can be lumped into two main categories:

1. Shots where the stars appear as stationary specks or points of light.
2. Shots where stars appear as streaks, taking advantage of the rotation of the Earth.

To capture meteors (or northern lights or the Milky Way), exposing for points of light is generally best because it allows the shooting stars to track across the frame — an effect that requires the camera to remain totally still and the exposure time relatively short.

The 500 Rule

The wider your lens, the longer you can leave the shutter open without turning stars into streaks.

A handy but rough tool for figuring out how to avoid noticeable blur, or unwanted star trails, is the 500 Rule. Take the number 500 and divide it by the focal length of your lens (whether it's a digital SLR or a point and shoot, this is typically displayed in millimetres). The result is the maximum time in seconds before trails will appear.

For example, a 14 mm lens gives you a maximum exposure time of 36 seconds. A 24 mm lens allows you a 21-second exposure, and so on.

Note that because camera sensors have improved, the traditional 500 Rule is no longer one-size-fits-all, and you may see it referred to as the 450 or 600 rule, depending on your camera. But 500 can still be used as a rough guide, then you can experiment to see what works best for you.

If your camera lets you adjust the aperture, you can do some more fine-tuning. Combined with an aperture of 2.8 (remember, the smaller the number, the bigger the aperture hole and the more light the lens is allowing to pass through to the sensor) and an ISO setting that isn't introducing too much grain into the image (let's just say somewhere between ISO 3000 and 6400, which is generally safe on most modern dSLRs and point-and-shoots), the 500 Rule should yield a pretty satisfactory first frame.

From there, you will need to fine tune based on what looks good to you, the amount of ambient city light affecting your shot, and the characteristics of your particular camera.

While it's easy to get bogged down in the technical aspects of camera settings and exposure times, keep in mind that the most significant factor when shooting the night sky, or anything, is light. All you can do is control how much or how little light reaches the camera's sensor. Shooting is like cooking and the amount of spice is up to you.

The darker the better

Getting away from bright city lights will dramatically increase the chances of getting a crisp, dark sky against which the stars will really pop out.

Use a heavy tripod with a locking ball head to keep the camera as still as possible during the exposure. You don't want a shaky camera blurring the stars, so this means no holding the camera in your hands while you're shooting.  

Don't have a tripod or a bulb-release to trigger the shutter?

Make a small sandbag out of an old sock or use a shoe as a support. Even a pile of rocks or the ground can work really well to prop your camera at the right angle to catch the patch of sky you're after.

Using your camera's timer function, frame up the shot as best you can, hit the shutter, put the camera down on the support (or back away from the tripod), then wait for the click before touching the camera and checking your capture.

Many cameras, including most dSLRs, allow for exposures up to 30 seconds — plenty of time to capture the night sky and, if you're lucky, a shooting star or two will have streaked across the frame.

If it's a meteor shot you want, employing the 500 Rule to get the maximum exposure time without trails in combination with a high rate of fire increases your chance of capturing a shooting star, or several. An interverlometre (basically a timer sold separately for most major camera brands, or sometimes built-in to the camera and accessed through menu settings) will allow you to shoot continuously without touching the camera.

Star trails

To get a circular effect in the stars in your photo (taking advantage of the rotation of the Earth), look for the 'B' for bulb release on your shutter control dial (or in the manual control settings of many new digital point and shoot cameras). Use that setting with an old-fashioned bulb-release cable (or your interverlometre) to hold the shutter open as long as you like.

A higher f-stop or aperture, or a lower ISO setting, can come in handy here if you are after a shot of the stars completing a full rotation or stretching all across the frame.

A cool technique for star trails is to focus on the North Star, Polaris, and to keep the shutter open for several hours such that the stars appear to trail in a full circle around the fixed point.

There are also techniques involving shorter exposure times (employing the 500 Rule) and editing software to 'stack' dozens or even hundreds of images taken over several hours to give the appearance of movement in the stars. This technique will allow for a final image that includes both star trails and shooting stars.

Quick recap:

1. Get to a dark location, away from sources of starlight-killing city lights. The Dark Sky Finder is a handy tool for determining how far off the beaten track you'll need to get.

2.  Keep your camera steady with a solid tripod. Shooting at night requires holding the shutter open longer — for several seconds, minutes or even hours — as opposed to the 10ths or 100ths of a second needed for your typical daylight shot.

And to find out the best angle to capture the sky from any point on the planet, download the Photographer's Ephemeris.

Happy shooting.

[If you get some good shots of the northern lights or night sky, we'd love to see them. You can upload them to CBC here.]