Pentax’s Astrotracer is a game-changing feature created with night photographers in mind. It has strengths and weaknesses. But overall, this feature alone makes the now “old” Pentax K-1 and K-1 Mark II the perfect cameras for astro-landscape photography even in 2021.
The Pentax K-1 Mark 1 was first released in 2016 and was Pentax’s first 35mm format digital camera. Now almost five years since the release of the original K-1, there still isn’t a camera on the market with anything remotely close to the Pentax K-1 and K-1 Mark II in terms of features with night photographers in mind.
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The K-1 was one of the highest megapixel DSLRs available, using a 36.4-megapixel CMOS sensor when released. Now, with many 35mm format cameras eclipsing the 40-megapixel range with some going over 60, the K-1 may seem to be falling behind.
However, the K-1ii still comes with a very inexpensive price tag of $1800 for the body, which most other manufacturers undoubtedly struggle to match when it comes to flagship models. The original K-1 can now be had for as low as $900.
Packed with features, the K-1 and K-1ii have plenty of dynamic range and are equipped with Pentax’s notoriously tough weather sealing. They continue to be near-perfect cameras for landscape photographers.
However, the Pentax camera system isn’t without its faults.
Issues With the Pentax K-1 and K-1 Mark II
Years after their release, complaints still plague the K-1 and K-1ii about their 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, a slightly faster autofocus system and internal upgrades weren’t enough to keep some Pentaxians from abandoning the brand.
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. It is also available for 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, unique to Pentax’s lineup, sealed my fate as a permanent Pentax shooter and I continue to use my Pentax K-1, K-1ii, and K-3ii.
What is Astrotracer?
To explain it in layman’s terms, 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 using an equatorial mount.
An equatorial mount (or tracker) is a motorized device that goes between your tripod and telescope or camera. It compensates for the Earth’s rotation to “track” the position of the Milky Way and other objects and stars in the sky.
A good budget-friendly 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 essentially eliminates the need for an equatorial mount, especially if you’re doing astro-landscape photography.
To learn more about star trackers, see our article on How to Use a Star Tracker.
How does Astrotracer work?
The technology involved with Astrotracer is nothing new or remarkable. It only 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, some 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. It 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. BEFORE you start calibrating the in-camera GPS on the K-1, K-1ii, or K-3ii, there are a few things you need to keep in mind.
Large metal objects like cars, gazebos, or metal buildings can interfere with your GPS calibration. Being near them may result in a miscalibration.
Your phone’s signal, signals from some wireless shutter releases, and heavily-populated areas with many phones and power lines can also interfere with the GPS calibration.
Also, you can sometimes have issues with getting a proper calibration if shooting from inside washes, canyons, or ravines. The GPS calibration is best done in an open area away from vehicles, buildings, and heavily-populated areas.
Step 1
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.
Step 2
Go to the K-1’s “Settings 2” menu and select the “GPS/Electronic Compass,” menu item.
Step 3
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 see a “Calibration Complete” notification once you’ve successfully calibrated your GPS. If the calibration is unsuccessful, then try walking around. Move a few feet in different directions or waiting a minute for a possible better signal. I have successfully calibrated my GPS in one try but have also failed to calibrate it several times in one night.
NOTE: Under the Camera 3 > Astrotracer menu, you can also perform a precise calibration to make Astrotracer more accurate when tracking the sky.
By performing the precise calibrations, you will be able to shoot easily with some telephoto or super-telephoto lenses with ease.
Step 4
Check to make sure you have a GPS signal. You will see a small GPS signal indicator. It 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.
Step 5
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 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 your sensor’s pixels’ size to determine the maximum exposure time before star trailing will appear.
Astrotracer does an excellent job rendering both rules almost obsolete (for Pentaxians.)
Astrotracer is far from being on par with a tracking mount in real-world testing, 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, I used the Pentax K-1’s Astrotracer feature with Pentax’s new D FA* 50mm f/1.4 lens. I shot 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 for a Pentax K-1 with a 50mm lens mounted.
Several K-1 owners, myself included, are now regularly using Astrotracer.
Astrotracer In the Field
Despite the multiple steps required to set up Astrotracer, the feature is straightforward to use. I’ve found that using Astrotracer does not change my in-field techniques for images where I’d be blending a separate sky and foreground.
The only real change (if you’re new to tracking) is you 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 excellently, but still has some limitations.
Single Exposures are Impossible
As mentioned above, turn Astrotracer off when you’re shooting a foreground or want to shoot single exposures. It is impossible to shoot (sharp) single exposures with Astrotracer. Since 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. This is 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,” Pentax-user 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 appears with lenses under 24mm. The center of the image will be 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 up to 200mm (or more.)
Read my review of the Pentax 85mm f/1.4 for astro.
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 the 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.
Pentax K-1 Astrotracer / Pentax D FA 24-70mm f/2.8 @ 48mm, f/2.8, ISO 3200, 30 Seconds.
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 found. All 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.)
Sky: @36mm, f/2.8, ISO 3200, 1 minute
Pentax K-1 with Astrotracer / Pentax D FA 24-70mm f/2.8
This feature has helped me increase my images’ quality tremendously and has proved to be an extremely convenient camera feature that has other uses.
Professional Uses
Astrotracer is also a unique feature that comes in handy for journalists like myself. (I am a landscape photographer and photojournalist.) Journalists are expected to deliver unedited or lightly processed, authentic depictions of scenes.
National Geographic’s former “Your Shot” photo guidelines said, “Composites are allowed… To be eligible for publication in National Geographic Magazine, the images must be combined parts made at the same time.”
Foreground: @ 15mm, f/2.8, ISO 1600, 2 minute
Sky: @15mm, f/4.0, ISO 6400, 1 minute
Pentax K-1 / Pentax D FA 15-30mm f/2.8
The Pentax Astrotracer, in this unique case, allows photojournalists to shoot a blend with a tracked sky without moving my camera a single inch. This technique means our work’s quality can increase significantly without being unethical in our image creation.
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.
The Pentax K-1 with Astrotracer has forever transformed the way I shoot my night images. It has sealed my fate as a lifelong Pentaxian.
As a bonus, I can use the money I could have spent on an equatorial mount to travel to my next location. I guarantee I’ll be calibrating my camera’s GPS once the sun goes down!
More Pentax Articles
– Pentax K-1: The True Best Night Photography Camera
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4/25/19
Updated: 1/19/20 AM v=9308
- Pentax Astrotracer Guide – 2021 Edition: What it is and How to Use it - January 21, 2021
- What’s In My Camera Bag #3 – Milky Way Edition - September 22, 2020
- Learn to Shoot the Night Sky with Sigma Ambassador, Babak Tafreshi - August 16, 2020
You forgot to mention the precise calibration under the Astotracer menu. Not the one under the GPS menu. I always do both calibrations when using Astrotracer.
I didn’t even know about the precise calibration! Thanks for telling me about that Tom! I’ll have to try it out and update the article.
Hey aaron, great article. Do you need to calibrate the astrotracer each time you move the tripod?
No! Once your GPS has been calibrated, you’re fine! If you turn your camera off, it may be another story!
Hi Aaron, just wondering if you recalibrate the Astrotracer for a new shot after you’ve turned it off to capture the foreground for the previous set up.
Hey Bryan! As long as you don’t turn your camera off or your camera’s GPS off, the GPS will remain calibrated. The GPS calibration is what it says; it calibrates the GPS system. Astrotracer just uses information from the GPS to move and rotate the sensor.. Hope this helped! Thanks!
Hi Aaron! Yes, thank you. I appreciate your response and this page. It’s hard to find info on the astrotracer.
I know it is! I’ve gotten a lot of positive feedback because so little information is available. I’m glad it helps!
Nice article. I have a K-3II, which also has Astrotracer built-in. It’s what sold me on the camera, frankly. I use it often, usually with vintage Pentax prime lenses from 28mm to 300mm. Yup, 300mm. I easily do 20 seconds at 300mm and stack many shots to get longer exposures (up to 260 in one case). A few examples here: https://www.astrobin.com/users/AlenK/
One correction to a point in the comments: Calibration should survive turning the camera off. It certainly does on the K-3II. I have even successfully used a previous calibration after returning to the same physical location on a later night.
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