Pentax’s Astrotracer is a game-changing feature created with night photographers in mind. It has its strengths and weaknesses, but overall, this feature alone makes the Pentax K-1 and K-1 Mark II perfect cameras for astro-landscape photography.
In early 2016, Ricoh Pentax finally entered the full-frame DSLR market with their highly anticipated K-1. It quickly gained praise from longtime Pentaxians and big-name photographers across the globe. Tony Northrup even stated in his review that he’d rather have the K-1 instead of the Nikon D810 or Canon 5DS R for landscape photography.
Not only was it one of the highest megapixel full-frame DSLRs on the market at the time, using a 36.4 megapixel CMOS sensor, it also came with a very inexpensive price tag of $1800 for the body, making it one of the most affordable full frame cameras on the market.
Packed with features, heaps of dynamic range, and equipped with Pentax’s notoriously tough weather sealing, the K-1 continues to be a near-perfect camera for landscape photographers.
However, it isn’t without its faults.
Issues With the Pentax K-1
Years after its release, complaints still plague the K-1 about its slow autofocus system, limited native lens selection, and a severe lack of aftermarket lens support.
With the announcement of the Pentax K-1 II, loyal Pentaxians were hopeful. The predecessor to Pentax’s first full frame camera had the potential to be a real jack-of-all-trades camera.
Unfortunately, an ever so slightly faster autofocus system and minor internal upgrades weren’t enough to keep some Pentaxians from abandoning the brand for good.
I, myself, almost switched from Pentax to Nikon because of these concerns until I used Astrotracer, the star tracking feature built-in to the Pentax K-1 and K-1 II.
Astrotracer is also built-in to the Pentax K-3 II and available in the Pentax KP, K-70, K-5, K-5 II, K-5 IIs, K-30, K-r, K-50, K-3, K-S1, and K-S2 when used with the Pentax O-GPS1 clip-on GPS unit.
This feature, which is unique to Pentax’s lineup, sealed my fate as a permanent Pentax shooter.
What is Astrotracer?
Put merely, Pentax’s Astrotracer is a function that acts as an in-camera star tracker. This feature allows photographers to shoot longer exposures without star trailing and without adding an equatorial mount.
An equatorial mount is a motorized device that goes between your tripod and telescope or camera and compensates for the Earth’s rotation to “track” the position of the Milky Way and other objects and stars in the sky.
A good equatorial mount can cost around $400. This type of mount can also go for well over $1000 depending on build quality, country of manufacture, and how much weight the mount can support.
A small tracking mount like the iOptron SkyTracker Pro weighs 2.5 pounds (1.2 Kg). That means a tracker also takes up precious space and adds more weight to an already cramped camera bag.
Astrotracer eliminates the need for an equatorial mount, especially if you’re doing astro-landscape photography.
To learn more about star trackers, see our other article on How to Use a Star Tracker.
How does Astrotracer work?
The technology involved with Astrotracer is nothing new or particularly remarkable. It uses the camera’s built-in GPS and sensor stabilization system. What is remarkable is the way Pentax uses them together.
In previous camera generations from various manufacturers, lenses had built-in image stabilization systems. Image-stabilized lenses use several small motors shifting optical elements to compensate for shake.
In a camera with sensor stabilization, the compensation for camera shake is in the sensor. The camera shifts the sensor on several axes to compensate for unsteady hand movement when image stabilization is turned on.
Many modern mirrorless cameras and DSLRs have a GPS receiver. Camera GPS systems record exact locations that images are taken for future reference or to help better organize your catalog of photos.
Pentax Astrotracer is a feature that very effectively uses the camera’s sensor stabilization in conjunction with the camera’s GPS. The sensor stabilization system uses data from the camera’s GPS to move the camera sensor to match the position of the stars in the sky.
When Astrotracer is active, and you are shooting, it is as if your camera’s sensor free-floats and matches the position of the stars while your tripod, camera, and lens are locked to the Earth allowing you to shoot longer sky exposures without star trails.
How Do You Set Up Astrotracer?
Astrotracer is a simple feature to use on the Pentax K-1 and K-1 II, but there are still a few steps involved to set up your camera correctly to use it.
Turn your camera on, set your camera to “Bulb” mode and calibrate the camera’s GPS.
Start by pressing the GPS button on the top of the camera next to the smart dial; an orange light next to the button will indicate the GPS is on.
Go to the K-1’s “Settings 2” menu and select the “GPS/Electronic Compass,” menu item.
Select “Calibration” and follow the on-screen instructions. It tells you to rotate your camera on three different axes at least 180 degrees.
You should get a “Calibration Complete,” notification once you’ve successfully calibrated your GPS.
Check to make sure you have a GPS signal. You will see a small GPS signal indicator that looks like a satellite on the top of your settings or live view screen when your GPS is on. Once it turns green, you’re ready to shoot.
The last step is to turn on Astrotracer.
When your camera is in live view mode or displaying camera settings, you can press the “Info” button on the back of the camera to go to a grid of icons. One of which is the Astrotracer icon, which looks like a shooting star with a square box “reticle” surrounding the star.
Once you turn Astrotracer on, you’re ready to shoot tracked images.
Camera Settings with Astrotracer
Most photographers with experience shooting the night sky have heard of the ever-changing “500/400/300 Rule,” for exposure times. Some have also heard of the newer “NPF rule,” a much more exact formula used to calculate exposure times. It factors in the size of your sensor’s pixels to determine the maximum exposure time before star trailing will appear.
Astrotracer does an excellent job rendering both rules almost obsolete (for Pentaxians.)
In real-world testing, Astrotracer is far from being on par with a real tracking mount, which can track the sky for 5 to 10 minutes or longer.
Rumor has it; you can track the sky for up to 5 minutes with Astrotracer. But I’ve only successfully used an exposure time of 4 minutes with almost no trailing occurring.
During my recent tests, using the Pentax K-1’s Astrotracer feature with Pentax’s new D FA* 50mm f/1.4, I was able to shoot perfectly sharp images, consistently, using a shutter duration of 1 minute without any sign of trailing.
For comparison, the “NPF Rule,” calculated by the PhotoPills app, recommends a max exposure time of 2.29 seconds on the Pentax K-1 with a 50mm lens mounted.
Several K-1 owners, myself included, are now regularly using Astrotracer.
Pentax K-1 owner, Jake Werth said, “The fact that I can easily get away with a 60s exposure at 35mm, where any other DSLR would have to shoot 10 seconds or less is incredible.” (Jake is an Albuquerque, New Mexico-based landscape and travel photographer.)
Astrotracer In the Field
Despite the multiple steps required to set up Astrotracer, once it is set up, the feature is straightforward to use in the field.
I’ve found that using Astrotracer does not change my in-field techniques for creating composites or for images where I’d be blending a separate sky and foreground.
The only real change (if you’re new to tracking) is when using it, you’ll have to remember to turn it off if you’re not shooting the sky. For single exposures, shooting in Astrotracer mode is nearly impossible, more details below.
Limitations and Issues
I had my Pentax K-1 for over a year before I tried Astrotracer. It’s a feature of your camera that sounds too good to be true.
In my experience, it works, but still has some limitations.
Single Exposures are Impossible
As mentioned above, you should remember to turn Astrotracer off when you’re shooting a foreground or want to shoot just one exposure.
It is impossible to shoot (sharp) single exposures with Astrotracer because the camera sensor is moving and your foreground is not; the ground will absolutely come out blurry every time.
Exposure Times are Still Limited
The camera sensor can only move so far before it runs out of its range of motion. This range of motion limits your exposure times significantly, mainly when you use longer focal lengths because moving objects, like stars, shot with longer focal lengths appear to move faster.
In the case of Astrotracer, the sensor’s physical movement limitation results in much shorter exposures with a max exposure time of about 5 minutes, often less than 1 minute at focal lengths over 50mm.
Not Wide-Angle Friendly
Astrotracer also does not work well with wide-angle lenses.
“The only downside is that with super wide-angle lenses, it struggles to shoot over about 45 seconds without trailing in the corners,” Jake Werth said. “From about 15mm to 24mm is the only focal range where a tracker would produce better results.”
In my tests using Pentax’s D FA 15-30mm f/2.8, the distortion from the lens under 24mm means the center of the image is sharp, but the corners still have some severe trailing (not coma) even stopped down.
Because of wide-angle distortion, the Astrotracer function works best for astro-landscape photography between 24mm and 70mm.
Despite these limitations, Astrotracer is a feature that significantly extends the length of your exposure time; far beyond what the “400 rule” or “NPF Rule” recommends.
My “A-Ha” Moment
In August 2018, I first tried Astrotracer in New Mexico’s Bisti Badlands.
Before going to Bisti, I camped and hiked around El Malpais National Conservation area, shooting for a few days. At night, I was pointing my camera at a partially cloudless sky trying to figure out how to use Astrotracer. Once I was happy with my results, I didn’t shoot any night images until I got to Bisti.
It didn’t come in the field. (Though I was excited about shooting tracked images.) My “a-ha” moment came weeks later when I first sold some prints from my trip to Bisti Badlands.
Before using Astrotracer, I was accustomed to having somewhat noisy astrophotography prints and accepted it as the norm. When it came time to print the image below in the requested 16×20” size, I clearly remember how excited I was to see it on paper. The image was tack-sharp, the colors were absolutely beautiful, and no noise was to be found thanks to shooting at a considerably lower ISO. (I used to shoot the Milky Way at ISO 12,800, now, I generally shoot between ISO 800 and 1600.)
This feature has helped me increase the quality of my images tremendously and has proved to be an extremely convenient camera feature that has other uses.
Astrotracer is also a unique feature that comes in handy for journalists like myself. (I am a landscape photographer and journalist.) Journalists are expected to deliver unedited or lightly processed, authentic depictions of scenes.
National Geographic’s Your Shot photo guidelines say, “Composites are allowed… To be eligible for publication in National Geographic Magazine, the images must be combined parts made at the same time.”
The Pentax Astrotracer, in this unique case, allows photojournalists to shoot a composite with a tracked sky without moving my camera a single inch. This technique means the quality of our work can increase significantly without being unethical in our creation of images.
Final Thoughts on the Pentax Astrotracer
Pentaxians and non-Pentaxians alike should try out this incredible feature at least once. It makes astro-landscape photography more accessible and easier to do.
It has forever transformed the way I shoot my night images and has sealed my fate as a lifelong Pentaxian.
I now love astro-landscape photography more than ever, and I’m planning several trips this year around shooting the Milky Way.
As a bonus, I can now use the money I could have spent on an equatorial mount to travel to my next location, where I guarantee I’ll be calibrating my camera’s GPS once the sun goes down!