What is a Star Tracker and Why do You Want to Use One?
A Star Tracker is a device that rotates your camera and can be a handy tool for astrophotography. I love using my Star Adventurer for wide-field nightscapes. Due to the earth’s rotation, we see the stars move across the sky. When you are photographing the night sky, your exposure time is limited because the stars begin to trail – the camera sensor picks up the movement of the stars through the night sky. If you want pinpoint stars – or close enough – in your images, there are a few considerations. How far stars move or trail across your frame depends on your focal length, camera resolution, and shutter speed. The more you zoom in on the stars, the faster you see trails forming instead of having pin point stars. PhotoPills has a module called Spot Stars which can help you figure out how long you can shoot for to get accurate pinpoint stars or barely noticeable trails.
Tracking is one of the ways you can deal with noise and get more light into your sensor while shooting at night. The tracker moves your camera at the same rate the stars move through the sky, allowing you to take longer exposures and use a lower ISO if you choose. You can check out my Milky Way Photos Before and After Editing blog for more details and other methods.
How to Set Up A Star Tracker
I have been using the Sky Watcher Star Adventurer for years. It is solid, reliable and relatively easy to use once you have the set up figured out. The gear I have is the Star Adventurer Photo Package with the Equatorial Wedge. It has an 11lb payload capacity, so you can use longer lenses and heavier gear. The longest lens I have used is my Nikkor 70-200mm f2.8, and I actually did it without a counterweight (it is better use a counterweight).
The Camera Store TV and I recorded a tutorial on how to set up the Star Adventurer. The steps are also listed below in this blog.
Step by Step Star Tracker Set Up
- Roughly figure out your composition and where you want your camera and tripod to be.
- Find the North Star: it is between the Big Dipper and Cassiopeia. The two stars on the end of the Dipper’s cup will point to Polaris. You can also use an app like Sky Safari on your phone to help orientate yourself.
- Set up your tripod so that it is level. The Star Adventurer Equatorial Wedge has a level on the base, and you can mount this directly to the tripod right away if your tripod doesn’t have a level. As you set up, it is a good idea to point the wedge to approximately where the north star is and then level the tripod.
- Set the Equatorial Wedge for your latitude.
- Attach the body of the tracker and make sure the polar scope is approximately pointing at the North Star.
- Polar Alignment (more on this later).
- Attach the fine-tuning mounting assembly, and then attach your camera.
- Compose your image.
- Turn on your tracker to the star symbol (celestial tracking) and take your sky image(s).
- Turn off the tracker and take your foreground image (in the sky image, the foreground will be blurred due to the camera movement).
- If the tripod moves or you shift anything at any point in this process, you will have to start over to get proper Alignment of the scope.
Polar Alignment
Polar Alignment is the trickiest part of the process, but luckily with a wide-angle lens, you don’t have to be that accurate – just pretty close. I’ve used up to a 200mm focal length, but I did try to be more accurate for that one. For the alignment process, I’ll refer you to the tracker manual, which has some helpful diagrams. If you are struggling with this process, you can line up Polaris approximately on the cross-section of the polar scope and still get good results using 1-2 minute exposures and wide-angle lenses. If you want to do deep sky imaging, you will have to be much more accurate. To figure out where Polaris should aligned, I use Polar Scope Align Pro. When I am shooting off the grid, I take screen shots at different times to reference later.
Tech Tips
Practice Inside First
The best time to figure out how to set up your star tracker is when you are comfortable and have light. Some muscle memory can also help when you are out in the dark and want to minimize how much light you are using to preserve your night vision.
Practise putting all the pieces onto the tripod you will use out in the field. Do this in order and pick a point to the be North Star to ensure everything goes on in the right direction. Put your camera gear and various lenses and test out balancing with the counterweight.
Practice Outside when it’s not Exciting
It’s frustrating to miss a moment or mess up a good composition or opportunity because you don’t have a good handle on setting up and using your equipment. Once you have everything figured out indoors, head out on a night when there is no pressure to capture something amazing and practice setting up and aligning your tracker.
There are many factors that will affect how the process goes when you are outside. These include uneven ground, wind, the cold, wearing gloves (you can test this inside, too). The sky doesn’t have to be completely clear for practice, you just need a good enough view of Polaris. I have taken clients out when the moon was 80% to practice using and setting up a star tracker.
Reflections are Tricky
When you are using a Star Tracker for a scene that has reflections, you may want to do some extra steps. Take the sky shot(s), take the foreground shot(s), then take water shots. If you want nice reflections, with no trailing, the water shots will have to be shorter (you can take multiple and then stack for noise).
Here is an example where I had different parameters and edits for different components of the image: sky, foreground, and water.
Sky: ISO1600 f2.8 14mm 120s x5 Stacked for Noise using Starry Landscape Stacker
Foreground: ISO3200 f2.8 14mm 30s x 5 Stacked for Noise in Photoshop
Water: ISO3200 f2.8 14mm 30s x 5 Stacked for Noise using Starry Landscape Stacker
All pieces were put together in Photoshop.
If you’d like to book a workshop on how to use a Star Tracker I’d love to work with you! This can be done during a Private Night Photography workshop, or you can email me to develop a custom program.