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Long exposures are one of the most popular, and stunning forms of photography, because they often embody a sense of motion in a single photograph. What if you combine long exposures (as in, very, very long) with astrophotography? Star trails are one of the most mesmerizing things you can photograph using just about standard equipment. Although the theory is very simple (you simply need to shoot a 30 minute exposure, right?), it is much harder to master in practice.
Lets get down to business. I’m a huge fan of any photo made at night. This is hands down my favorite type of photography. I especially enjoy star trails because of the perspective it gives to the landscape from the Earth’s rotation. That being said, let’s debunk a myth right now. Some people think the only way to make star trails is with a single 30 minute exposure. Shooting a single 30 minute plus exposure is totally fine but the photo will be super noisy, due to fixed sensor noise. The better way of doing this is by taking 70-90 exposures at 30 seconds each and stack them afterwards. Stacking photos results in a cleaner final image. Some photographers like to shoot hundreds of photos and stack those. I normally shoot for about 30 to 45 minutes. At 30 seconds a piece, you will get two images every minute.
First of all, get out of a city or brightly lit area. Light pollution is going to ruin everything astrophotography related, not just star trails.
I usually choose my location with something interesting in the foreground like mountains, an old building or a dead tree to give the entire photo perspective. I never photo just the stars alone. In addition, it is important to choose a Northern view with the North star in the frame to take advantage of the Earth’s rotation and the view it creates when stacked. (And vice-versa for those of you in the Southern Hemisphere.) Finally, I always make sure there will be no extra lights like headlamps, automobile headlights, etc in my shot because a single exposure with extra light can ruin the entire stack. Always make sure you are shooting in a location with no light interruptions.
For star trail photography, always shoot when the sky is clear. A no-brainer. A bit of clouds is okay, but more than that and you’ll risk having interruptions in your star trails. That being said, the weather can change very quickly at night, so if you plan on shooting for more than a few hours, always check the weather in advance. Hopefully, there is an tool for astrophotographers wishing to see the cloud patterns and it is located here. An absolutely useful link to check out.
Don’t worry too much about this. Location and weather are much, much more important. But if you are more than just a beginner, the following information might be useful to you.
Having a partial moon to illuminate the foreground landscape is ideal. It balances the photo with light and exposure. However, on some lighter colored landscapes, a full Moon may be a little bright and overpower the stars. . However, it is always about balance. It is very possible to shoot star trails without any foreground illumination other than the stars, but I will always prefer some (although not too much) moonlight when I can get it.
As a general rule, you can make star trails with most any camera that has the ability to make 30 second exposures at ISO 200. This is usually the starting point for star trail exposures, and you should adjust the ISO accordingly after. When I photo the Milky Way, I only use a Full Frame DSLR because of its high ISO performance. But with stacking photos, 30 seconds at ISO 200 with a fast lens (f/2.8) and any DSLR is perfect. So I’ll use either my crop sensor or my Full Frame to make photos and then stack.
Camera – Any full-frame DSLR like a Canon 1D/5DMKIII/MKII/6D, a Nikon D4/D3s/D700/D600/D800/D4, etc, and other brands of full frame cameras are perfect. Any crop sensor (APS-C size) like that of a Nikon D3100/3200/D5100/D5200/D7000/D7100/D90/D80/D300(S), etc, or a Canon T2/T3/T4/T5/40D/50D/60D/7D, etc. As far as other cameras such as point-and-shoots or mirrorless are concerned, if they have the option to shoot in manual and set the exposure, aperture, and ISO, they should be fine. The take away here is find a camera that can shoot in manual (M mode) at ISO 200 for 30 seconds, without too much noise.
Lens – If using a DSLR, the best is a fast wide lens. My favorites are the Tokina 11-16mm f/2.8 on my crop sensor (APS-C) and my Samyang 14mm F/2.8 on full-frame. I always shoot wide open at f/2.8 and at the widest angle of view. Now most people get their cameras with kit lenses (18-55mm) and most of those lenses have a maximum aperture of f/3.5 at 18mm. I’ve done stacks with F/4 lenses and raised my ISO to 320. So a kit lens like a 18-55mm should be fine. However, make sure to focus it beforehand since not only will it have trouble focusing at infinity in dark light, there are no focusing marks on the lens whatsoever.
Tripod – A must have. This is VERY important for star trails (or just about anything else). You will need a very sturdy tripod to mount your camera on as you will be shooting for 30 or more minutes to make about 70 to 90 photos to stack. If your tripod moves even a little bit when shooting, your final product will result without the perfect curvature of the trail reflecting the Earths rotation.
Intervalometer – Some photographers prefer to use a wired intervalometer/remote. This device allows you program and setup an automated continuous cycle of 30 second exposures. This is really handy if you don’t want to stand by your camera for 30 or 45 minutes hitting the shutter button over and over every 30 seconds. Some of the newer Nikon and Canon models (and others) have built in intervalometers. However, if you don’t have any of the above, its really not that much work to setup a chair by your camera and just hit the shutter button every 30 seconds if you have a sturdy tripod. I use one like this. Or just search for Amazon or your favorite camera retailer for “Intervalometer”.
Don’t forget to have a fully charged battery and a memory card with enough room to store a few hundred files if you’re shooting for a couple of hours. Having a power outage during the middle of the shoot sucks.
1. Find your spot and secure the camera to the tripod. Once you have your view, don’t move the camera when shooting.
2. Set your camera to M, aka Manual mode.
3. Set your aperture to its fastest aperture : f/2.8, f/3.5, etc.
4. Make sure that your lens is focused at infinity. Use autofocus to do this, and lock focus afterwards. If for any reason (e.g. lack of light) you can’t autofocus on anything, try to align your focus with infinity using the manual focus marks. However, this is much more imprecise, especially when shooting wide open, since the infinity focus point varies depending on temperature.
5. If using a zoom lens, set it to the widest view. 18mm, etc.
6. Turn off Autofocus and set your lens to the infinity mark. Look at the lens focus ring and find the focus mark (line) and line that up with the infinity symbol (the sideways 8).
7. Set your exposure to 30 seconds if you are manually hitting the shutter button. You will hear the shutter open and then close after 30 seconds. Just hit the shutter button again and repeat 70-90 times. Or you can use and intervalometer to automate the process.
8. Set your NR (Long Exposure Noise Reduction) to OFF. This is VERY important. NR takes an additional 30 seconds after EVERY photo to reduce noise. If turned on, you will end up with gaps in the stack. 30 second exposures aren’t noisy enough to warrant long expsosure NR, and even if they were, ending up with gaps inbetween star trails isn’t fun.
9. RAW vs. JPG – I shoot in RAW and process my RAW photos in Nikon Capture NX or Photoshop. But you will be fine to shoot and JPG and still get some amazing results.
10. Set your camera to ISO 200 and turn off Auto ISO. Take a test photo and make sure the exposure looks good. Too dark? Adjust your ISO up to 320 and then take another photo. If the photo looks a bit dark, don’t worry. You can add light and contrast in your post process.
Stacking and post-production
I stack my photos in Photoshop. In photoshop, you simply import all your pictures as separate layers and set the layer mode to “Lighten” to get the star trails. Use a mask or eraser to weed out the airplane trails and other annoying objects in the photograph.
That being said, there are lots of other free pieces of software out there to do it. A free, quick and easy way, is to visit http://www.startrails.de and download their stacker. It will automate the whole process for you, so there is no tweaking involved to get star trails. Once the stacked image is created, adjust contrast and brightness using another free photo editor such as Picasa from Google after you have completed the stack, or use Adobe Lightroom. A detailed guide on image stacking is on the way!
About the author: Brian Spencer is a New Mexico based amateur/semi-pro photographer behind this amazing tutorial. We have slightly modified some parts for additional clarifiation. Check out his blog blog on photography here and follow him on Facebook and 500px!
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