A cell phone camera probably has a resolution of ~1 arcminute (about the resolution of the human eye). The Hubble has a resolution of ~0.05 arcseconds. The HD

A cell phone camera probably has a resolution of ~1 arcminute (about the resolution of the human eye). The Hubble has a resolution of ~0.05 arcseconds. The HDST would have a resolution of ~0.002 arcseconds. So to get comparable resolution to Hubble the probe would have to be at a distance of (.05 / 60) * 270,000 AU ~ 225 AU and a distance of (.002 / 60) * 270,000 AU ~ 9 AU to beat HDST. A camera on such a telescope would probably be of somewhat higher resolution, however. In fact, it would probably be at the diffraction limit, which for a ~1 cm aperture in visible light would be closer to ~10". This would increase the distances above by a factor of 6 or so. Resolution isn't the only thing, though. The contrast is extremely important. A little probe in the Alpha Centauri system would be able to take clean images of any planets in the system. A telescope in our solar system trying to directly image these planets has to contend with contamination of light from the stars.