Amateur astronomers engage in many imaging techniques including film, DSLR, LRGB, and CCD astrophotography. Precise focusing of telescopes and astrographs is critical to performing astrophotography. An astrograph (astrographic camera) is a telescope designed for the sole purpose of astrophotography. Popular applications include photography, videography, and astrophotography. Afocal photography is a form of astrophotography long practiced by astronomers. Astrophotography and CCD imaging are also very popular. There are also cameras specifically designed for amateur astrophotography based on commercially available imaging sensors. In 1909, Miethe began working with an observatory for astrophotography. A niche use for these cameras is in field of astrophotography. Lucky imaging (also called lucky exposures) is one form of speckle imaging used for astrophotography. HDR+ is similar to lucky imaging used in astrophotography. Special films are used for the long exposures required by astrophotography. Directly taking images of night sky is also a part of astrophotography. In 1883, Roberts began experimenting with astrophotography. Night Sight is based on a similar principle to exposure stacking, used in astrophotography.