One of my favorite uses for a digital camera is wide-field astrophotography. That definition covers a lot of things, but basically, it means I like to point my lens at the night sky and capture what it holds. Of the countless photo opportunities “out there,” two of the most unusual and captivating effects you can achieve are star trails and time-lapse sequences of the stars in motion. (Opening image ©David Mcalpine)
Here’s the cool thing: The best star trail images are taken very much like a time-lapse sequence. In other words, they’re created from a series of exposures blended with software to produce the final image. The difference is in how the exposures are combined. So, just for fun, let’s do one overnight shoot and create both.
Note: although this will be a fairly long read, it’s not an intensive course. This is a quick, fun project that will teach you the basics for this kind of photography. If you find you enjoy it, you’ll find plenty of great tutorials on the Internet. If there’s enough interest, I’ll follow up with some detailed lessons.
This short video clip shows one possible set of results from a shoot like the one in this project.
Basic star trail images and time lapse movies don’t require a lot of fancy stuff.
What You’ll Need
Any good project outline starts with a list of equipment and/or materials, right? Basic star trail images and time lapse movies don’t require a lot of fancy stuff. Sure, sliders, rotators and such are cool, but for this project, we’re going to keep the camera stationary. Here’s the list:
For the shoot:
- a DSLR or mirrorless camera (Sorry, we’re not covering film cameras this time.)
- a normal to wide-angle lens (I prefer wider, like the Irix 15mm or 11mm.)
- a STURDY tripod (I recommend attaching a sandbag or similar weight to the center
- an intervalometer (shutter release timer – Some digital cameras will have one built in.) Note, if you don’t have one, you can get a decent one on Amazon.com starting at less than $20. You won’t regret the investment.
- a small flashlight or headlamp to check settings, etc.
- something to keep yourself occupied for several hours
After the shoot:
A computer with the appropriate software: Lightroom and Photoshop are both good options. There are also several inexpensive and even free applications that can process your exposures.
Common sense should dictate the rest of your list, depending on where you plan to shoot. You’re going to be outdoors at night, so plan to take along what you need to stay warm, dry and safe. You’ll get the best results away from city lights, so this is a great project for a camping trip.
Don’t forget to check the weather forecast and the phase of the moon.
Get your gear together, find a place to get away from the light pollution and get there before sunset. Setting up in the dark is obviously slower and more difficult, with more room for error. Here’s a handy little app to help you find a nice, dark location: Dark Site Finder or you can grab one of these apps for your smartphone: Dark Sky Finder for iOS or Dark Sky for Andriod.
Don’t forget to check the weather forecast and the phase of the moon. A bright moon in the sky will make it difficult to get the best images of the stars. I use Stellarium for just about any information on the stars and planets at any time. (It’s free and awesome.)
Make sure your camera and intervalometer batteries are fresh and fully charged. Also, make sure you have sufficient room on your memory card. You don’t want to disturb the setup once you’ve started shooting!
Once you’ve arrived at your shooting site, determine what area of the sky you want to shoot. Here’s an important consideration: If you want to create completely circular trails/sequences, you’ll need to point your camera at Polaris (assuming you’re in the Northern Hemisphere – the Southern Cross will get you close on the other end of the world).
The farther away from the polar axis you shift your view, the wider the arcs of the stars’ paths will become. Consider the different effect on your star trail images and time-lapse movies. Both can be interesting.
I recommend including some of the surrounding scenery in your frame. This can create a better sense of depth and you can even fool around with things like light painting during the shoot. Get creative.
Set up your tripod on a stable surface, add weight, mount your camera, lens and intervalometer and frame your shot according to the decisions you made above. Remove straps and other devices that may blow around and cause camera shake. (You can strap your intervalometer to a tripod leg.)
If your lens has a calibrated infinity setting like Irix lenses, you can simply set and lock your your focus there.
Disclaimer #1: All of these settings are subjective. I am recommending safe settings that should produce decent results from your first attempt. Adjust as needed or as you see fit.
- WB: Some photographers use the Auto setting. I prefer to set mine on Daylight and adjust as necessary in processing.
- Exposure Mode: manual (M)
- ISO: 800 is a good place to start – higher if your camera’s sensor rejects noise well.
- Aperture: One or two stops below maximum
- Shutter Speed: Set to bulb (B) if possible, to allow the intervalometer to control it.
- Other: Set long exposure noise reduction to ON if available.
Focus carefully. If your lens has a calibrated infinity setting like the Irix lenses, you can simply set and lock your your focus there. If not, it’s best to verify the focus setting using a bright object and your camera’s magnified Live View. Remember that this will increase the drain on your battery, so try not to take too long.
Disclaimer #2: See Disclaimer #1.
- Delay: Set a few seconds’ delay for the start of your sequence, just to be sure any vibration caused by pushing the start button will subside.
- Long (Bulb): 20 to 30 seconds. The longer the shutter is open, the more likely you’ll have noise in the image, so use 20 seconds if you’re shooting with a smaller sensor.
- Interval: The length of time between exposures will determine how much time you “compress” into the length of your movie, i.e. how fast or slow things move, as well as how long it will take to shoot the sequence.The interval must be long enough to allow each exposure to complete and save to your memory card or you’ll have gaps in the sequence. The size of the files and the speed of your camera processor as well as the memory card all affect saving time. If you’re unsure how long each will take, set your interval equal to the shutter speed. For example, a 30-second exposure and an interval of 30 seconds would give you one shot per minute. Here’s how the rest of it plays out at that setting:
A standard frame rate of 24 frames per second means that you’d need 240 frames for 10 seconds of video, so at 60/hour, that means 4 hours of shooting time. How many exposures you can fit on a card will depend on many factors, but a good rule of thumb is to expect about 250 – 300 images per 8GB of card space. That would translate to a bit more than 20 seconds of video (8 hours of shooting time) on a 16GB card. That’s assuming that your battery holds up for that long.
- Number: In some cases, it’s convenient to know exactly how many frames you want to shoot in a sequence. For this shoot, I recommend leaving the setting to “infinite”, which usually means setting the number at zero. This leaves you a little bit of leeway, just in case something worth recording happens before you stop shooting.
Here’s a sequence with some slightly different results.
Shooting the Sequence
Once you’ve completed all the steps above, all that’s left to do is push the start button when you’re ready to start shooting. Then you can sit back and relax or get ready to add any light painting or other effects to the foreground of the shots. Most importantly, try not to let anything interrupt the shooting or disturb your camera setup.
Back at Home
Alright, you’re back home and all rested up from the night out under the stars. Time to process those photos and create some awesome images and an amazing time-lapse video. As already mentioned, there are several choices available in processing software, so I won’t attempt to cover all of them. I’m going to walk through the steps for Photoshop CC.
Before you start: It’s best to check your RAW photos and edit them for exposure, contrast, white balance, etc. and make any adjustments before you start. You can edit them in batches with Adobe Camera Raw, which comes as a free add-on with Photoshop CC. When you’re happy with the individual images, go ahead and export all of them as JPG files to a separate folder. (You’ll need those to create the time-lapse movie.)
A few hundred images will take a long time to process.
You may want to work with only a portion of your shots from the session for creating star trail images, but experimentation is the best way to get the results you want. Start with 100 or so exposures and work your way up. A few hundred images will take a long time to process.
While there are a few methods you can use to stack images in Photoshop, there’s a lesser-known way that’s fast and easy and works well with star trails: the Statistics script. We’re going to use it here so you can see your final image quickly.
From the menu, select File/Scripts/Statistics. Set the Stack Mode to Maximum. Click Browse and select a consecutive set of your RAW images to stack. Don’t check “Attempt to Automatically Align Source Images.”
When you click OK, Photoshop will import the selected photos one at a time and blend them based on the brightest points (Maximum). When the script completes, you’ll have a Smart Object with stacked images combined. This will take some time.
At this stage, you can experiment with different Stacking Modes to see what effect you like best. Select Layer/SmartObjects/Stack Mode and choose the mode you’d like to try. You’ll get some crazy results, but you can keep changing modes until you find the one you want to use.
Finally, select Layer/Flatten Image and make any final adjustments you like, then save the finished photo in the format you like.
OK, it’s time to create that cool movie. This time, we’re going to work with those JPG files you created during the “Before you start” step.
Go back to Photoshop and select File/Open, then browse to the folder where you saved your JPG files. Select only the first file in the series. Then check the little box next to “Image Sequence”. Click OK and select a frame rate of 24. (You can change this and other settings later if you like.)
When the images have opened, you’ll have a Video layer in your Layers palette. If you don’t see a video timeline on the bottom of your window, select Window/Timeline from the menu. You can edit the video layer just like any other in Photoshop, with filters, adjustment layers, etc. I’d recommend keeping the edits to to a minimum for your first attempt.
When you’ve made any changes, select File/Export/render Video. Check your filename in the dialog box and be sure to note and/or change the Folder so you’ll know where to find the finished product. The export settings shown in the image below should work well.
Click “Render” and the export process will start. This might be a good time to make a fresh pot of coffee, call the kids or whatever you do to pass the time.
When the process completes, go to the folder where you saved the movie and double-click on it. If you’ve got a player configured on your computer, you should see your star time-lapse in all its glory.
That’s a Wrap!
Now that you’ve created your first (maybe) star trail image and time-lapse video, you should have a good foothold on how the process works. As I stated at the beginning of this tutorial, it isn’t intended to make you an expert in either field; it’s simply a fun weekend project to help you “get your feet wet” and demonstrate how one shooting session can give you the images for both finished products. For Irix lens owners, it’s also a good demonstration of the value of a calibrated infinity setting with a click-stop, a focus lock and a high-quality wide-angle lens.
Now, go show off your new stuff!