Photometric observations using orthogonal transfer CCDs

Orthogonal transfer CCDs (OTCCDs) were developed to compensate for real-time image motion, essentially providing tip/tilt corrections without additional optics or moving parts. Because of the complex gate structures of OTCCDs, their ability to provide high-precision photometric observations and their use as highspeed photometers were unclear. We detail new observations obtained with the OPTIC camera at the University of Hawaii's 2.2 m telescope on Mauna Kea that explore both of these areas. We find that OTCCDs provide equally good results in terms of typical time-series differential photometry (compared with typical CCDs) and that their high-speed photometric application is superb. Using point-spread function-shaping techniques, we obtained time-series photometric observations with precisions of less than or similar to660 mumag per 180 s integration. Extending this technique to very bright stars, the potential to reach differential precisions near 10(-5) per exposure is investigated.