Pentax K-1 Review
The Pentax Astrotracer feature uses the Shake Reduction mechanism to track stars in the sky for a short period of time. While it's not a replacement for a professional star tracker for very long exposures, it can easily increase feasible exposure times from a few seconds to well over a minute for typical star photos.
Since the K-1 has on-board GPS, the Astrotracer can be used without the need for any external accessories.
To enable it, the GPS must first be powered on using the physical GPS button. Thereafter, it is enough to access the main menu and turn the astrotracer on. Note that the astrotracer icon can also be added to the customizable Control Panel.
This is also a good opportunity to disable the GPS light via the illumination menu, as the light shines right in your face by default and can be distracting in the darkness.
Enabling the Astrotracer
Put the camera in Bulb mode and instead of a "B", you will see the Astrotracer icon in the upper left corner of the screen (if not, press the green button). The first time you use this feature, and every time you change the location, you will need to press the exposure compensation button and carefully rotate the camera along each of the three axes to calibrate the electronic compass. Continue calibrating until the camera shows the "complete" message. Without this, the Astrotracer will not work properly.
We had no trouble obtaining good results after a single calibration, but results may vary based on your geographical location and how steadily you hold the camera during calibration. A tripod is not necessary, and you can certainly calibrate while standing rather than sitting.
Bulb mode turns in to Astrotracer mode
The Astrotracer supports shutter speeds up to 5 minutes (300 seconds), and all these shutter speed settings can be selected right in the camera without a remote. Minimally, however, we recommend the use of the 12-second self-timer to reduce the risk of vibrations.
Realistically, the sweet spot for the astrotracer generally lies within the 60 and 90-second range. The sharpness of the scene will depend on your focal length. As with normal exposures, longer lenses reduce the length of time during which you won't be able to see star trails. It's also normal for the corners and edges to be a bit soft (especially with ultra-wide lenses), so bear this in mind.
The test photo above was taken at 70mm with the D FA 24-70mm F2.8 lens. Notice how the 60-second exposure with the Astrotracer shows nearly no motion, whereas things are a blur in the 30-second conventional exposure.
Download the full-size JPEGs (processed from RAW): with Astrotracer and without. The full scene reveals some objects in the foreground which you can use to observe the path that the Astrotracer followed.
While the Astrotracer makes the K-1 unique, it's the full-frame sensor that enables cleaner star photos than ever before. Overall, this camera is an excellent choice for fans of astrophotography thanks to the flexibility that it offers.