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We have developed a new method to correct dark current at relatively hightemperatures for Charge-Coupled Device (CCD) images when dark frames cannot beobtained on the telescope. For images taken with the Antarctic SurveyTelescopes (AST3) in 2012, due to the low cooling efficiency, the median CCDtemperature was -46$^\circ$C, resulting in a high dark current level of about3$e^-$/pix/sec, even comparable to the sky brightness (10$e^-$/pix/sec). If notcorrected, the nonuniformity of the dark current could even overweight thephoton noise of the sky background. However, dark frames could not be obtainedduring the observing season because the camera was operated in frame-transfermode without a shutter, and the telescope was unattended in winter. Here wepresent an alternative, but simple and effective method to derive the darkcurrent frame from the scientific images. Then we can scale this dark frame tothe temperature at which the scientific images were taken, and apply the darkframe corrections to the scientific images. We have applied this method to theAST3 data, and demonstrated that it can reduce the noise to a level roughly aslow as the photon noise of the sky brightness, solving the high noise problemand improving the photometric precision. This method will also be helpful forother projects that suffer from similar issues.

A new method of CCD dark current correction via extracting the dark information from scientific images