As shutter speed is the limiting factor in taking pictures of the night sky, we often seek out more expensive lenses that open up that bit more or check Fstoppers if there’s a new low-light, high-ISO king of cameras on the horizon. But what if I told you that there’s a device you can use today, with the camera and lens you already have, that has the potential to capture places that are light years away from Earth?
What Is a Motorized Mount?
DSLR astrophotography is a very limiting genre in terms of what you can do with camera settings. We’ve discussed ISO settings and noise reduction before, but today we’re going to take a look at shutter speed. Because of our planet’s rotation, the shutter speed on wide-angle lenses is limited to about 30 seconds before stars start to show signs of streaks. Before we go on, however, we’ll call shutter speed by its proper name: exposure time. “Speed” implies short exposures, and we are nowhere near 1/500 of a second throughout this article.
Here’s where specialized instruments that seek to overcome the rotation of the Earth come in.
Do you see those huge telescopes moving with the night sky? Imagine your camera at the end of a telescope and hours of exposure time that capture the very faintest objects in the night sky. You’re now about to understand the importance of accurate tracking.
These mounts are also called “trackers” because they track the stars across the night sky as the Earth rotates, freeing you of exposure time limitations. Well, not exactly, but we’ll cover this in this review of the LighTrack II from Fornax Mounts.
Photography in the Field
The best results can be obtained in the most remote locations. Locations that are free from light pollution, from city lights, and car lights as well. As a landscape photographer, photography means to me that I’m taking pictures away from home. You should be aware that this is a specialized device that needs its own power source. That should not be a problem when shooting from your backyard. And you can get spectacular results from doing so. But the supplied 12V cigarette lighter cable will only reach a meter or two from your car to your tripod. So you will need to buy a separate power supply for taking the LighTrack II to the most remote corners of the globe. But combine this with a light pollution filter and there are a lot of exciting subjects to photograph from your backyard alone.
The Stuff You Need
Of course there are no sharp images of stars and nebulae without a solid (that means heavy) tripod. A heavy tripod will prevent the setup to become top-heavy and ensure a good shoot. As stated before, you’re going to need a 12V DC power source to shoot away from home or your car. Fieldwork requires a battery, or a mains adapter will work for shooting from the backyard. I picked up this excellent 4 Ah (it’s enough to shoot an entire night) battery from Tracer that’s in wide use in the astro community. Also, an intervalometer is a good purchase in any sort of long-exposure photography. I’ve gone for a cheap €20 eBay option with all the bells and whistles and it is fine.
You do need to consider which package is right for you. Fornax Mounts has three available LighTrack II packages. The cheapest option comes in at €450 and only includes the mount itself. Buying this means that you already have a method of polar alignment and that you’re going to have to invest in a heavy-duty second ball head or wedge separately. The second package includes the polar scope and sets you back €499, while the full set also includes the FMW-200 wedge that enables you to track the stars with just the tripod you already have.
Putting the wedge, polar scope and the mount together takes about half an hour without looking at the instructions. It’s that simple. But a question arises when you put this hefty unity atop your tripod. How does polar alignment work exactly?
Deploy your tripod and make sure it’s level. Attach the camera to the mount and forget your camera and what you want to photograph for a minute. You are working with a precision instrument that is designed to overcome a single thing: the rotation of the Earth. In order to make the LighTrack II (or any other motorized mount) work, you’re going to need to align the rig toward a particular point in the sky. In the northern hemisphere, you’re aiming for a patch of sky near the North Star (Polaris). Yes, not the actual North Star.
Polar alignment isn’t that difficult once you've done it once or twice. But if you aren’t familiar with telescopes, here’s a bit of beginner advice that isn’t stated anywhere in the instructions. What you see in the scope is a mirror image. I use an Android app that’s called Polar Finder, which shows the reticle of the polar scope and gives the position of Polaris based on your location and your local time. You then align the wedge exactly as the app suggests by comparing the view through the scope and the app’s graphic.
Then you will discover that the wedge doesn’t actually rotate 360 degrees and that you’ll have to reposition the entire tripod towards Polaris. This is something you might find to be a nuisance, but consider that polar alignment is a very, very precise job — of course it doesn’t rotate 360 degrees. Just be sure to roughly place your tripod so that you get it right the first time.
Two thumb screws on the wedge provide very accurate control over the rotation the mount, while a heavy duty set of knobs on the side of the wedge gives you all the control you need over the height adjustment. These two mechanical adjustments determine the azimuth and altitude of the mount in order to perfectly align your polar scope with either celestial pole.
Start Your Tracking
On the LighTrack II, you’ll find a set of buttons. The first button switches between tracking modes. “Sidereal” means that it follows the night sky, which is the setting for deep sky astrophotography. With the lunar and solar settings, you can track the moon and sun respectively. But a warning: do not go out and take long exposures of the sun unless you are absolutely sure what you’re doing. The final option is half sidereal tracking, which is a good starting point if you want to combine landscape and astrophotography into a single image. The next button lets you choose between the northern and southern hemispheres, and the last two buttons will slew (move) the mount toward either end of the tracking gears. The tracking starts automatically when you turn the mount on with the on/off switch on the bottom and there’s a very subtle audible signal to tell you it’s active.
Here's a quick, single image of the difference between tracking and not tracking for 4 minutes at 90mm.
[beforeafter label1="Not Tracking" label2="Tracking"]
Speaking about the tracking gears, the LighTrack II is supposed to be one of the most accurate trackers out there at the time of writing. Unfortunately, I don’t have any comparison, so I’ll leave verification to others who do. Every unit is supplied with the results of its factory calibration in the form of a graph. And trust me when I say that if the periodic error is +/-1 arc over 8 minutes, the tracking is pretty damn accurate.
It tracks for a period of two hours before you need to slew the mount back to its starting point. The maximum recommended load is 6 kilograms and as for the maximum focal length, it’s not recommended to go above 300mm. At 300mm though, it’s safe to shoot 6 minute exposures. But with an autoguider and counter weights, it’s possible to extend these specs even further. The LighTrack II comes autoguide prepared.
Where were we? Ah, the fun part and the waiting game. Now don’t go thinking, “Two hour exposure, check.” When we discussed noise in an earlier article, I didn’t pay much attention to long exposure noise. Or rather, thermal noise. That’s an entirely different sort of noise than signal noise. Without flooding your poor brain with another chapter on the mathematics of reducing thermal noise, I just want to tell you what you can do to get the best possible results. It’s simple: keep the sensor cool. The longer the exposure time, the longer electricity will flow through the sensor’s circuitry and the warmer it will get. As a DSLR astrophotographer, with a modern camera, you should not shoot hour-long single exposures, but shoot multiple images of the same thing with small intervals in between to let the sensor cool down again and minimize the effects of the periodic error of the tracker. You then merge the resulting images in specialized software to add all the captured photons. Take it from astronomers that this is the best way to maximize your results on DSLRs.
You’re left with a set of images that’s about two hours worth of shooting. I’ve aligned (registered) and stacked the images in the free Deep Sky Stacker and processed the result in both Lightroom and Photoshop.
Astrophotography isn’t a genre for beginners. You really have to invest a lot of time in learning the ropes of managing exposure, noise, polar alignment, and even develop a familiarity with the night sky. Deep sky photography is about capturing the things you do not see with the naked eye and motorized mounts are perfect to bring the science behind all this to backyard astrophotography.
The Fornax Mounts LighTrack II is a very high build quality tracking option that certainly won’t let you down in this regard. The challenge at the end of the day (pun not intended) is not the quality of LighTrack II, but to really educate yourself to handle such a specialized device. Fornax Mounts could supply more information targeted at photography enthusiasts buying their first motorized mount, because there is a lot to take in if you’ve never dabbled in astrophotography before. But once you get the hang of it, it’s going to take a very long time before you reach the limits of this mount’s top capabilities.
4.5 out of 5 stars.