Astrotracer
The Astrotracer function works in the bulb shooting mode and can be found in the GPS section of the in-camera menu, because it requires the optional GPS unit (around £175) in order to work. In short, astrotracer eliminates star trails during long exposures (up to 5mins), which is achieved by using information from the GPS signal, the angle of view and focal length of the attached lens. A calculation is made for the necessary physical movement of the imaging sensor during the exposure, in line with the star trails. According to Pentax, this function is unique to its cameras that use electro-magnetic sensor-shake reduction. Previously, an equatorial drive was needed to remove star trails.
I mounted the K-30 to a tripod and recorded an image for 4mins at f/8 and ISO 100 with the function activated, and repeated the same exposure with it disabled and compared the results (below). As you can see, with astrotracer enabled, the stars appear stationary and, consequently, the landscape is blurred. Conversely, with the function disabled, the star trails are evident while the landscape is crisp. With a little patience and the use of editing software, it is possible to combine the crisp elements of each exposure for a striking final image.
