Blog, Prints & Photography Lessons from Edinburgh and the Lothians

The easy guide to photographing star trails

So, star trails. Striking images certainly but surprisingly easy to do with the right software.

First things first, to make your life a million times easier, if you’re using a Mac, download StarStax and on a PC, Startrails.exe, Google them, easy to find and both a free download. This is the software that will combine your final set of images into the star trails shot. If you really enjoy spending ages with Photoshop you can blend each image separately but these make life a lot easier.

Other than that all you need is a camera capable of doing 30s exposures, a tripod, remote control and a nice dark area where you can see plenty of stars. Don’t underestimate the power of light pollution to ruin a shot, the example below was taken in my garden in a built up area of Edinburgh, the light pollution is easy to see so try and get out of town somewhere.

The effects of light pollution

With everything in place you now need to locate Polaris. It’s not essential but if you can keep Polaris in the image then the stars will nicely rotate around it. To find it look for the Plough, one of the more well known star clusters. It’s in the shape of a soup ladle (roughly) so follow the handle around to the scoop and locate the last 2 stars in the Plough. From there in a straight line around 3 times as far away as the 2 stars are from each other will be a slightly duller star, this is Polaris. Or even easier, get one of the smartphone apps such as Star Walk on the iPhone and use that to locate Polaris.

With this done compose your image. You want a 30s exposure that doesn’t overexpose any foreground interest but shows up a lot of stars in the preview image. Usually you’ll be around f7.1 or wider and ISO400 or above to get what you want. The more stars you see on the preview, the more trails you’ll get in the final image. Shoot in RAW mode too if possible. I’ve also found that the wider the lens the better. You’ll want to be on manual focus, and with focus set to infinity.

Once you’re happy with the shot it’s time to settle in for the long haul. You’ll need at least 40 shots to get a decent trail in your final image. The more the better but you’ll be there longer to get them. A decent compromise is around 60 shots if you are picking up a lot of stars. You’ll either need to fire the shutter every 30s or if you have a programmable remote set it to 30s exposure with 32s delay to give the camera time to process each image.

With your shots in the bag, it’s time to thaw out and start the process magic.

First thing to do is to process the first RAW image, how you do it is personal preference but make sure that you get a decent mix of stars in the sky, the sky kept darker and don’t blow out any foreground. Once you have a image you’re happy with, save the settings and then process every image with the same settings. It doesn’t take that long to do with ACR or Lightroom, and save each as a jpg.

Now, open all the jpg’s in your processing software, either StarStax or Startrails.exe and start it off processing them using blend lighter to combine the images. After less than a minute you’ll have the stacked image. If you find cloud has passed through the shot you can exclude these images and start again but remember you’ll get breaks in your trails. Best plan in this case is to try and blend again missing the offending frames and see if it’s any better, sometimes the cloud doesn’t matter that much.

Save the final image and open it in Photoshop or similar. From here you can do your final adjustments, usually darkening the sky, upping contrast and that it, and this is what you should get…

FRB Star Trails 29 Dec

This panoramic shot was slightly different to do. Had I shot this with the bridges at the bottom of the shot the verticals of the bridges would have been hugely distorted, to get around this I shot a single long exposure image with the bridges in the middle of the frame where the distortion isn’t an issue. I then moved the camera to where I wanted the bridges in the final shot and shot the multiple star images. I finally took the long exposure image, moved the bridges to the bottom of the shot and extended the sky with content aware fill, I then blended in the star trails image and selectively erased the bridges until I had the correct verticals version overlaid with the star trails. A bit more mucking about but a much more pleasing final image.

Forth Bridges Pano Star Trails

So, a final checklist…

Warm clothes if doing this in winter, a simple MUST have.
Sturdy tripod
Camera capable of 30s exposures
As wide a lens as possible
StarStax or Startrails.exe software
Remote control for camera
A clear night
A dark(ish) location

That’s it. Off you go and shoot those stars!

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4 responses

  1. Thanks for the blog post – I’m going to try this out myself!

    January 1, 2012 at 11:01 am

  2. Wow!!! Wow!! Wow!

    Stunningly. Spectacular. Stuff.

    January 2, 2012 at 2:28 pm

  3. Colin Walker

    This is a great blog.
    I have wanted to take pictures like this for a while. Can you explain why it’s better to take say 20 x 30s exposures and merge them rather than one exposure of 10 minutes.

    March 1, 2012 at 9:22 pm

    • It’s to do with digital noise Colin, a single 10 minute exposure will heat up the sensor which in turn leads to digital noise in the image, even at low ISO. So, to get around this a series of shorter exposures are used. Add to this that it’s much easier to work out a 30s exposure and get it right rather than a 10 minute one and it’s a much easier method.

      March 2, 2012 at 9:26 pm

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