Spec­tac­u­lar star trails

Use these straight­for­ward tech­niques to record the move­ment of the stars across the night sky

NPhoto - - Feature -

Tra­di­tion­ally, shooting star trails with film-based cam­eras re­lied on shutter speeds of min­utes or even hours to cap­ture the move­ment of the stars across the night sky. But these ex­po­sure times will pro­duce too much noise on dig­i­tal cam­eras. As such, it’s bet­ter to shoot a se­quence of im­ages us­ing a much shorter shutter speed and then com­bine them later. The other big ad­van­tage with this tech­nique is that un­like many other cre­ative op­tions for shooting the stars, you can get great star trails im­ages even when there is some light pol­lu­tion.

1 Take POLE PO­SI­TION

Fix the cam­era in po­si­tion, fo­cused on the stars – and ide­ally pointed close to the pole star (see Step by step). You can ei­ther use con­tin­u­ous drive mode and just lock the shutter release on your re­mote, or you can use an in­ter­val­ome­ter to take a se­quence of im­ages.

2 Cap­ture the Trails

To cap­ture sig­nif­i­cant trails with a wide-an­gle lens, you’ll need to keep shooting for at least 15 min­utes, which works out at 30 ex­po­sures of 30 sec­onds each. The longer you shoot for, and the more ex­po­sures you take, the longer the star trails will be in your fi­nal im­age.

Once you’ve com­pleted your se­quence of star trail im­ages, you also need to take a fi­nal ‘dark frame’. This is a shot taken us­ing ex­actly the same shutter speed, ISO and aper­ture as your main im­ages, but with the lens cap in place. This dark frame is used when you come to com­bine the shots in soft­ware; it will help to re­duce noise and the vis­i­bil­ity of any ‘hot pix­els’, which ap­pear as white dots in long-ex­po­sure im­ages. For this to work suc­cess­fully, the dark frame needs to be taken im­me­di­ately af­ter you’ve shot the fi­nal im­age in your star trail se­quence.

3 Com­bin e the im­ages

Once you’ve taken your se­quence of im­ages, plus a dark frame, you need to com­bine them. Load each star shot as a sep­a­rate layer in Pho­to­shop (or your pre­ferred photo-edit­ing soft­ware), then change the blend­ing mode of all lay­ers, apart from the bot­tom one, to Lighten. Load the dark frame on top of the Layer stack, and change its blend­ing mode to Dif­fer­ence.

This process is fine for a few im­ages, but if you’ve taken 30 or more shots it’s a bit slow. The eas­i­est way to com­bine lots of shots is to use soft­ware to au­to­mate the process. A pop­u­lar op­tion is Star­trails for Win­dows, avail­able to down­load in the Soft­ware sec­tion at www.star­trails.de. Al­ter­na­tively there’s StarS­taX, which is avail­able for both Win­dows and Mac OS X via the Soft­ware sec­tion at www.markus-en­zweiler.de.

Look for a sta­tion­ary fore­ground de­tail, such as this rock for­ma­tion in Arches Na­tional Park, USA, to add in­ter­est and drama

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