Stargazing is such an exquisite experience; it’s no wonder we’ve been doing it since the dawn of time. Astrophotography is taking the stargazing experience and bringing it home with you. I remember the first time I photographed the Milky Way - seeing the core of our galaxy brightly lit on the back of my camera was truly invigorating; however, there is only so far standard equipment can take one when shooting the stars before issues like noise, coma and star trails start to arise. An excellent way to combat these issues is to use a Star Tracker.
Taking a typical Milky Way photo without a tracker requires 3 elements (besides a dslr (preferably full frame) and wide-angle lens) in order to ensure enough light is reaching the camera’s sensor to create a suitable exposure: A long-exposure, a high ISO, and a wide aperture. Though these three elements are required to properly expose the Milky Way, these setting push the camera to its limits and evidence of this can be found in the resulting image. A long-exposure is an unavoidable necessity but due to the Earth’s rotation, star trails begin to occur which decrease star clarity. To get a decent exposure your shutter speed should be around 15-30 seconds depending on your focal length. Even at this relatively short exposure, star trails can be seen. A high ISO setting is also required; however, using one increases the amount of noise in the image. The last important consideration when shooting the stars on standard equipment is a wide aperture, preferably f/2.8 or wider; however, shooting that wide-open creates our third issue in quality - coma.
Using a Star Tracker is a one-stop solution to all of the issues identified above. A Star Tracker is a device that is first aligned to the North Star to then accurately track the stars. In other words, the tracker allows your camera to move in the exact speed and direction of the night sky. This enables photographers to use a lower ISO which reduces noise, a smaller aperture to avoid coma, and a longer shutter speed without the risk of creating star trails. In addition, because longer exposures are possible using a Star Tracker, a more centered and dynamic histogram with no clipping in the darks, greater color separation and detail can be achieved.
I was recently given the chance to try out the ECH-630 Astro Tracker from Slik USA. The very first thing I noticed about the Astro Tracker was its size - it’s astoundingly small and lightweight while the majority of other trackers I’ve tried have added significant weight and bulk to my pack. Even with the additional tripod mounts recommended for use with the Astro Tracker, the set-up remains compact and lightweight enough to fit in my camera backpack with a full frame DSLR and 2-3 lens’
The next thing I noticed about the Astro Tracker was its ease of use and relatively straight-forward set-up process. I first set up my tripod on firm and level ground. Once my tripod is set, I attach the tracker. When the tracker is securely attached to the tripod, two peepholes on the device are used to align the tracker to the North Star. One hole is slightly larger than the other with a 4 degree field of view to allow you to easily achieve alignment. The second hole is 50% smaller with a 2 degree field of view which is then used to fine-tune the alignment. I personally had a hard time seeing anything through the smaller hole at first, but I was able to use a laser to point at and illuminate the North Star, this made using the smaller hole much easier. Once the tracker is aligned, I attach my camera and set my framing and exposure, being extra careful not to bump the tripod now that it is aligned. Finally, it’s time to turn the tracker on, which is as easy as pressing three buttons: first turn the On/Off switch to On, next push ‘down’ on the directional pad to choose “Star North” (telling the device that I am in the Northern Hemisphere), then select ‘yes’ to confirm and now you are tracking and ready to start shooting! Once you are aligned, as long as you don’t move or bump the tripod, you do not have to do anymore alignment and are free to shoot and reframe.
To illustrate some of the advantages of using the ECH-630 Astro Tracker, I have attached some photos for comparison. My process consisted of first taking a tracked exposure for the sky (35mm f/4.0 iso1250 180sec), then I immediately took another exposure with the same settings but with the tracker off in order to achieve a proper exposure for my foreground. I took another exposure with the tracker off but this time using standard Milky Way shooting settings to compare coma, noise, and star movement (35mm f/1.4 iso2500 15seconds). In the side by side comparison you can very obviously see that the tracked exposure is the superior photo with no star movement or visible trails, no coma, less noise, and less lens vignetting.
Although this is not the best photo to compare histograms as I was unable to push my shutter speed longer due to light pollution, you can still see that the tracked exposure’s histogram is more centered in the side by side comparison which creates a better final result. A more centered histogram translates to more workable data once the image is brought in to Photoshop or Lightroom – there is more information to work with. This allows you to pull out greater contrast in the cloudy/highlighted parts of the Milky Way and also allows greater color variation and detail.
An additional advantage of using a tracker is that it forces you to shoot your sky and foreground separately. This is admittedly extra work, but ultimately yields much better results. You can use a smaller aperture to achieve a longer focal range and sharper results, a lower ISO to get less noise, and a longer exposure to get greater shadow detail. In addition to those advantages, using a tracker encourages the ability to edit your sky and foreground as separate layers, which I particularly like. This allows me to really push my contrast on the sky while I would never push it that far on my foreground. It also lets me do some hot pixel reduction on my foreground which does not do well on my sky because the software has trouble differentiating between hot pixels and stars and ends up removing stars as well as hot pixels. Take a look at the finished results here:
After working with this star tracker I highly recommend Slik USA’s ECH-630 Astro Tracker for use in photographing the night sky, especially for you adventure enthusiasts. At an affordable cost, the device enables photographers to photograph stars at a quality and resolution that blows non-tracked star shots out of the water. With its compact size and ease of use, the Astro Tracker is a convenient and advantageous tool that any photographer intending to shoot the night sky should consider adding to their gear.