Choosing a Star Tracker for Astrophotography
When it comes to astrophotography, a star tracker allows you to take better images. Your exposure lengths are no longer limited to 30-seconds or less due to a moving sky, and you can dial back camera settings like ISO and F-stop.
Equatorial camera mounts are designed to align with the polar axis of the night sky so you can take long-exposure images that are free of star trailing. Astrophotography demands long-exposure tracked images to collect as much signal (light) as possible, and that is exactly what a star tracker allows you to do.
This summer, I had the opportunity to review a new star tracker for astrophotography, the Fornax Mounts LighTrack II. From the mechanical design to the polar alignment procedure, this portable tracking camera mount is very different from any astrophotography mount I have ever used before.
It created the perfect opportunity to compare this camera tracker against some of the competing models in this category, in terms of overall user experience and performance. In this post, I’ll discuss the topic of using a star tracker for astrophotography, and which one I like using most.
Later that summer, I tested the Sky-Watcher Star Adventurer (Pro Package). This is an extremely popular choice for amateur astrophotographers in 2020, and for good reason. I tend to recommend this star tracker over the others in most situations.
The iOptron SkyGuider Pro, Fornax Mounts LighTrack II, and iOptron SkyTracker Pro
The star trackers shown above are capable of accurately tracking the night sky for long-exposure night sky photography. Each of them has their own strengths and weaknesses, from the portability factor to maximum payload capacity. I’ll do my best to explain why the overall user experience is the number one factor to consider when choosing a portable tracking camera mount.
How to Use a Star Tracker
A star tracker’s job is to match the rotation of the Earth so that you can take long exposure images (at nearly any focal length) of the night sky. To properly track the stars that appear to move across the night sky each night, a star tracker must be polar aligned and balanced.
To polar align an equatorial mount for astrophotography (including a small camera tracker), you need to adjust the altitude and azimuth of the base so that the polar axis of the mount is aligned with the celestial pole. In the northern hemisphere, we have the advantage of using the north star, Polaris, to aid in this process.
A portable star tracker with a ball head and DSLR camera attached.
Without using a star tracker, the stars in the night sky will begin to trail after about 15-30 seconds, depending on the focal length of the lens used. This is because the Earth is spinning on its axis, while the night sky is fixed. Amateur photographers using a stationary tripod can use the 500 rule as a guide for choosing the ideal shutter speed, but a star tracker removes this limitation altogether.
When a tracking camera mount is used, a small motor slowly rotates your camera in right-ascension, effectively matching the apparent movement of the night sky, and freezing it in its tracks. The image below shows you what a 3-minute exposure using a 400mm lens would like without using a star tracker.
Long exposure images (180-seconds) shot at 400mm with and without tracking.
Luckily for amateur astrophotographers and photographers, there are a lot of great star tracker options to choose from these days. Unlike a heavy equatorial telescope mount, a star tracker is portable, small, and lightweight. Because of their small size and compact profile, they’re usually a lot more affordable, too.
The star tracker category includes small EQ mounts that can carry a camera and lens combo, whether it’s for wide-angle Milky Way photography or deep sky imaging with a telephoto lens. Wide-angle nightscapes and Milky Way panoramas are the star trackers strong point. These types of projects usually involve traveling to a remote location, where packing light is necessary.
If you’ve ever seen a detailed photo of the Milky Way like the one below, chances are the photographer used a star tracker to collect sharp, long exposure images with their camera and lens.
The Milky Way from a dark sky location. Stack of 60 x 2-minute exposures at ISO 1600.
A star tracker will usually include a polar scope, which is used to help find the north celestial pole and adjust the mount accordingly. A star tracker that has been properly polar aligned will match the exact apparent rotation of the night sky to freeze deep sky objects in place.
Don’t expect these little units to carry a heavy telescope, although small refractors are an option if you’ve got a counterweight system to help balance things out. As you’ll soon see with the Fornax Mounts LighTrack II, a counterweight system is often an additional option from the base star tracker package.
In fact, a lot of the star trackers available online today come in a potentially confusing number of packages and bundles. My advice is that you invest in a system that can not only handle your intended payload (and then some) but also provide you with features that make imaging in the field easier and more enjoyable.
Popular Models in the “Star Tracker” Category
If you are a beginner in the world of astrophotography (see my beginners guide), investing in a tracking camera mount is the single biggest advancement you can make in terms of gear. You can now let the exposure time do the heavy lifting without relying on fast optics and high ISO settings to collect a decent amount of signal.
The following tracking camera mounts share many similarities, including the ability to track the night sky at different speeds. Before investing in a dedicated star tracker for landscape or deep-sky astrophotography, make sure the bundle you order includes everything you need to mount your camera and lens.
- iOptron SkyTracker Pro
- Sky-Watcher Star Adventurer Pro (& Mini)
- iOptron SkyGuider Pro
- Fornax Mounts LighTrack II
Which one should you invest your hard-earned money in for astrophotography? That will depend on the type of user-experience you are looking for, and my goal for this article is to highlight the key differences in the user experience for each mount.
If you’re just looking to shoot wide-angle astrophotography using a camera lens, I’ve got good news for you. All of the star trackers mentioned above are capable of accurately tracking the night sky for incredible long exposure images like the one below (including the most affordable option, the iOptron SkyTracker Pro).
Canon T3i and Rokinon 14mm F/2.8 lens on the iOptron SkyTracker Pro.
What They Do Best
These mounts are primarily designed for wide-angle astrophotography, meaning projects like Milky Way panoramas or mid-range focal length compositions using a telephoto lens in the 100-200mm range. That’s not to say that you can’t use a star tracker for high magnification deep-sky imaging, but that will demand the most of your tracker, and a require a diligent setup routine.
The portable nature of a star tracker often leads to some of the most memorable deep sky astrophotography sessions in the field, as they offer you the freedom to travel to a dark sky location without a trunk full of gear. One of the most incredible astrophotography adventures of my life was setting up an iOptron SkyGuider Pro and William Optics RedCat 51 telescope to capture the Carina Nebula from Costa Rica.
The Carina Nebula from Costa Rica (9-minute exposure using a star tracker and small telescope).
It simply wasn’t possible to bring my computerized telescope mount to this location (on a plane), yet a star tracker fit in my carry-on bag and allowed me to collect tracked images of the night sky from the middle of the resort. These are the kinds of adventures you can expect when you invest in a portable star tracker for astrophotography.
Key Benefits of a Star Tracker
- Quick Setup and Alignment
- Lightweight and Portable
- Great for Travel
- Built-in Battery Power*
- Great for Camera Lens Astrophotography
* The Fornax Mounts LighTrack II requires an external 12V power source.
From my personal experience using star trackers for astrophotography from the backyard and beyond, I believe the absolute most important aspect to consider is the user experience. If the star tracker is not easy to use in the field, or the process of setting up takes too long, you won’t use it as much. That’s all there is to it.
As any experienced amateur astrophotographer will tell you, your motivation to stay up all night and image will vary. Any additional friction between you and a successful image has a way of affecting your decision process of stepping outside on a less-than-perfect night.
Don’t forget about the tear-down process either. If the clouds roll in and it looks like rain is coming, a lengthy teardown routine can turn into a stressful situation. Star trackers can usually be carried inside the house with all elements attached in a moment’s notice. The same can not be said for a full-blown deep sky astrophotography kit.
A star tracker should allow you to quickly get up-and-running under a clear night sky. It should be a pain-free experience that provides the freedom and flexibility to take amazing astrophotography images wherever, and whenever you want.
All of these photos were captured using a portable camera tracker mount.
Which Star Tracker is Right For You?
I often see comments from beginners about being limited to a maximum exposure time using a particular mount before the stars begin to trail. My honest opinion is that these situations are almost always due to user error in the polar alignment and balancing procedure.
Each and every star tracker I have ever used for astrophotography was capable of sharp, 3-minute exposures using a focal length of up to 200mm. A portable star tracker must be accurately polar aligned and balanced to work properly. This may seem obvious to most people, but time and time again I see poor results being blamed on the hardware itself.
The iOptron SkyGuider Pro with a telescope attached.
My portable star tracking mounts have traveled with me to some amazing places and captured some of my favorite astrophotos. Both of the iOptron star trackers I am about to cover are extremely popular in the amateur astrophotography and nightscape photography community, and for good reason.
iOptron SkyTracker Pro
If you’ve watched any of my previous videos, you’ve probably seen the iOptron SkyTracker Pro in action. This ultra-lightweight star tracker is iOptron’s latest variation of their incredibly popular and affordable wide-angle astrophotography mount.
The SkyTracker Pro (not to be confused with the SkyGuider Pro) weighs just 2.6 pounds and houses everything you need for long exposure nightscapes in a little red (or black) box. A plastic box that is, with adorably simple controls to accelerate the RA axis to your intended target.
The iOptron SkyTracker Pro with a DSLR camera and wide-angle lens attached.
- Weight: 1.5 lbs.
- Max Payload: 6.6 lbs
- Max Useful Focal Length: 200mm
- Built-In Battery: Yes (Li-Poly 3.7V)
- Built-In Polarscope: Yes
- Autoguider Input: No
This camera mount was designed for wide-field nightscape images using a DSLR camera and lens. Many people have had great success using the SkyTracker with an ultra-wide-angle lens like the Rokinon 14mm F/2.8, all the way up to some heavier glass such as the Rokinon 135mm F/2.
It’s the most affordable star tracker I’ve used, and it has delivered exceptional results using a number of different camera lenses. One such instance was the time I used the SkyTracker Pro with my Canon EF 24-105mm F/4L Lens to shoot Mars and the Pleiades star cluster in the same frame.
The Planet Mars alongside the Pleiades Star Cluster. iOptron SkyTracker Pro and 24-105mm lens @ 105mm.
iOptron SkyGuider Pro
The SkyGuider Pro is a big step up from the Tracker, offering a heavier payload capacity, a more robust design, and the ability to autoguide your images. The iOptron SkyGuider Pro is a top contender in this category with stellar reviews from experienced nightscape photographers.
This portable EQ mount fits in the palm of your hand, yet can handle up to 11 lbs of imaging gear. With the counterweight kit attached, the SkyGuider has no trouble with larger telephoto lenses and even small refractor telescopes such as the William Optics RedCat 51.
The North America Nebula in Cygnus. iOptron SkyGuider Pro with William Optics RedCat 51 attached.
- Weight: 2.2 lbs.
- Max Payload: 11 lbs
- Max Useful Focal Length: 400mm
- Built-In Battery: Yes (Li-Poly 3.7V)
- Built-In Polarscope: Yes (Illuminated)
- Autoguider Input: Yes
Beginners often get tracking and guiding mixed up or assume that they both mean the same thing. Tracking is the act of matching the rotation of the Earth using an RA (right ascension) motor, with the axis of the mount aligned with the celestial pole. Guiding is a specialized astrophotography technique that uses a secondary camera to lock-on to a guide star and sends small commands to the mount to improve tracking accuracy.
The iOptron SkyGuider Pro includes an ST-4 autoguide port that allows you to autoguide using the appropriate cabling and software on your computer. Although autoguiding is a powerful feature that allows for even longer exposures (and the benefits of dithering), it requires additional hardware to run.
The William Optics RedCat 51 is a great match for the SkyGuider Pro.
For smaller loads, such as a DSLR camera and 50mm lens, you can simply attach a ball head to the 1/4″ threaded socket on the mount. Heavier camera lenses or small telescopes will need to be mounted to the declination plate and utilize the counterweight system (shown above.)
For those that prefer to polar align their SkyGuider Pro electronically, the iOptron iPolar device was designed to fit neatly inside of this camera tracker. Be advised, that once you make this modification to the mount (or order a version with the iPolar included), you lose an element of portability with the need for dedicated software control.
If you’re thinking about diving into the world of telescopes for astrophotography, I’d recommend the RedCat 51 Petzval APO to compliment the SkyGuider. This F/4.9 quadruplet apochromatic refractor is exceptionally sharp and delivers incredible wide-field images with a focal length of 250mm.
Sky-Watcher Star Adventurer
The Sky-Watcher Star Adventurer Pro is responsible for one of my favorite astro-images of all time, the Andromeda Galaxy. This portable star tracker is easy to polar align, and the pro pack comes with everything you could possibly need to mount your DSLR camera, lenses, and even a small telescope.
The following image was captured using a Canon 60Da and a William Optics RedCat 51, mounted to the Sky-Watcher Star Adventurer Pro. I stacked 100 x 2-minute exposures at ISO 1600 for an unforgettable shot of M31:
The Andromeda Galaxy captured using the Sky-Watcher Star Adventurer Pro.
When comparing the specs between the iOptron SkyGuider Pro, and the Sky-Watcher Star Adventurer Pro, you’ll notice a number of similarities. For example, the “Pro Pack” includes a counterweight kit, wedge base, and a built-in illuminated polar scope.
- Weight: 2.2 lbs.
- Max Payload: 11 lbs
- Max Useful Focal Length: 400mm
- Built-In Battery: Yes (4 x AA)
- Built-In Polarscope: Yes
- Autoguider Input: Yes
The Star Adventurer includes a built-in WiFi, Android/iOS App control for those looking to control projects such as time lapses with your DSLR. Like the iOptron models I mentioned above, the Star Adventurer includes modes for solar, lunar, sidereal, and half sidereal tracking rates.
I really like that the Star Adventurer can run on 4 AA Batteries. Although it may seem like a step backward from a rechargeable li-poly battery, this feature may come in handy when your taking pictures nowhere near a source of power. Sky-Watcher reports that these batteries can power the mount for up to 72 hours, more than enough time for a night or imaging or two.
I found the Sky-Watcher Star Adventurer Pro to deliver an exceptional user experience, right out of the box. The hardware and premium finishes of this portable star tracker really stood out to me, and I love the mounting bar and counterweight kit.
Using the Sky-Watcher Star Adventurer at the Black Forest Star Party in September 2019.
Fornax Mounts LighTrack II
Fornax is a company based out of Hungary, and they are no stranger to astronomical equipment. Fornax has been manufacturing astronomical mounts for nearly 20 years, working on professional astronomical projects such as the HATNet Exoplanet Survey (Hungarian Automated Telescope) for discovering exoplanets.
The Fornax Mounts LighTrack II looks and acts differently than all of the other star trackers I previously mentioned. It uses a friction motor drive system that slowly sweeps an arm across the base of the mount. The fine friction strip helps the LighTrack II maintain balance, and was designed with strict production tolerances.
Like the other star trackers mentioned, the LighTrack II has 4 tracking speeds. Sidereal, Solar, Lunar, and Half. The “half” speed mode can be used to create nightscape images with terrestrial elements. For example, if you wanted to capture an interesting wide-angle landscape, but want to expose the night sky longer – you can, without the landscape being blurred.
Fornax Mounts LighTrack II.
- Weight: 2.9 lbs.
- Max Payload: 14 lbs
- Max Useful Focal Length: 500mm
- Built-In Battery: No
- Built-In Polarscope: No (Additional Accessory)
- Autoguider Input: Yes
The bundle I received from Fervent Astronomy included the MMW-200 wedge to mount the tracker to my tripod, and the counterweight kit (that I have not tested yet). The hardware is impressive, from the aluminum alloy components to the carbon-composite plastic housing for the electronics.
However, there are 2 colossal differences between the iOptron and Sky-Watcher camera trackers and the LighTrack II. The first is, this mount requires an external 12V power supply. There is no internal battery inside of the LighTrack II. So, if you plan on traveling with this mount you’ll need to bring a reliable battery or find an outlet and extension cord nearby.
The second is that the LighTrack II will only track your subject for 107 minutes, before having to return the tracking arm to its starting position. Luckily, you can use the panning control knob of your ball head to keep the camera stationary during this process.
The good news is, once you’ve powered the LighTrack II up, you’ll benefit from incredibly accurate unguided performance. Fornax lists that peak-to-peak unguided tracking error is less than 2 arcseconds in 8 minutes. I can confirm that the unguided performance of the Fornax LighTrack II is incredible and that the 3-minute images I’ve captured at 400mm were razor sharp.
I captured the Lagoon and Trifid Nebulae on the Fornax LighTrack II (William Optics RedCat 51 refractor).
Capturing the Lagoon Nebula and Trifid Nebula region with the Fornax LighTrack II was one of my first experiences using the mount, and it was a good one. The images were 3-minutes each at an effective focal length of 400mm with my camera system, and the unguided exposures were excellent.
Here is a look a single 180-second sub exposure using the LighTrack II with my Canon 60Da, William Optics RedCat 51, and the OPT Triad Ultra filter. I’d feel comfortable going to 5-minutes, wouldn’t you?
A single 3-minute, unguided exposure using the Fornax Mounts LighTrack II.
If you’re comparing the Fornax Mounts LighTrack II with the iOptron SkyGudier Pro, the accessories needed to complete a “full” package will send you well past the price of the SkyGuider Pro. The iOptron SkyGuider Pro full package includes the wedge, polar scope, and counterweight package. These items must be added on to the original price of the LighTrack II mount and purchased as a bundle.
It’s worth mentioning, that perhaps the LighTrack II should not be in the star tracker category at all. Due to its increased payload capacity, autoguiding capability, and accurate tracking, you may want to consider it to be a bridge between a camera tracker and a traditional equatorial telescope mount.
Star Tracker Comparison Chart
Here are the bare bones specs of the star trackers mentioned in this post. The listed “longest useful focal length” is merely a point a reference. In reality, I believe all of these trackers could handle a 2-minute exposure using an even longer lens.
|Brand||Mount||Weight||Maximum Payload||Max. Useful Focal Length||Built-in Battery||Autoguide Port|
|iOptron||SkyTracker Pro||1.5 lbs.||6.6 lbs.||200mm||Yes||No|
|Sky-Watcher||Star Adventurer||2.2 lbs.||10 lbs.||300mm||Yes||Yes|
|iOptron||SkyGuider Pro||2.2 lbs.||11 lbs.||400mm||Yes||Yes|
|Fornax Mounts||LighTrack II||2.8 lbs.||13.2 lbs.||500mm||No||Yes|
I believe that any mount that wants to compete in the “star tracker” category should have a built-in power option. I realize that many people are accustomed to traveling with an external power supply for various devices, but I am not one of them.
The iOptron SkyGuider Pro (and SkyTracker Pro) include an internal, rechargeable, li-poly 3.7V battery that can be charged with a mini-USB charging cable. This simple design feature means that I’ll reach for the SkyGuider when traveling light, or setting up for a brief imaging session. If you want to travel to a remote location with the LighTrack II, be prepared to power the mount using the cigarette lighter plug from your car.
In the end, the best camera tracker for astrophotography will always be the one you use the most. You can have the nicest equipment in the world, but if it doesn’t help you accomplish your final goal (pictures) on a consistent basis, it’s time to reflect on why you got into this crazy hobby in the first place.
Other Popular Star Trackers Available
There are new tracking camera mounts popping up every year. The models discussed in this post are not the only options available. Here is a short list of some of the other star trackers available today:
- Sky-Watcher Star Adventurer Mini
- Vixen Polarie
- Slik Astro Tracker
- Omegon Mount Mini Track LX2