Pentax already makes a compact digital camera with built-in GPS so their announcement yesterday of a GPS unit for use with some of their digital SLRs is not too surprising. The $250 O-GPS1 GPS unit works with Pentax’s K-5, K-r and medium-format 645D cameras, and appears to do a bit more than just work as a GPS logger. It’s weather-resistant (something I sometimes worry about when using my Nikon GPS unit), and it even has an astrophotography function: it uses GPS, a compass and accelerometers to figure out where the camera is pointing, and activates shake reduction to reduce star trails in long-exposure images. (Considering the wide field of view in camera lenses when used for astrophotography, that could allow much longer exposures without having to resort to an equatorial mount.) Available in July.