86
7 The Astronomical Detector
Fig. 7.4 Bias frame from an SBIG 1301 CCD. The bright edge on the left-hand side is the noise
generated by the read process. (Image University of Hertfordshire)
Fig. 7.5 Dark frame from an SBIG 1301 CCD. The bright corner on the left-hand side is the noise
generated by the read process. The bright points scattered randomly across the frame are hot pixels,
as discussed below. (Image University of Hertfordshire)
Super Flats and Fringes
In some cases, it is necessary to take more advanced calibration frames, for example
when it is impossible to do a dome flat or when very high precision is needed. In
such a case, a super flat may be required.
In simplest terms, a super flat is a normalised flat frame constructed by taking the
mean of several on sky images that contain very few stars (no stars at all would be pre-
7 The Astronomical Detector
Fig. 7.4 Bias frame from an SBIG 1301 CCD. The bright edge on the left-hand side is the noise
generated by the read process. (Image University of Hertfordshire)
Fig. 7.5 Dark frame from an SBIG 1301 CCD. The bright corner on the left-hand side is the noise
generated by the read process. The bright points scattered randomly across the frame are hot pixels,
as discussed below. (Image University of Hertfordshire)
Super Flats and Fringes
In some cases, it is necessary to take more advanced calibration frames, for example
when it is impossible to do a dome flat or when very high precision is needed. In
such a case, a super flat may be required.
In simplest terms, a super flat is a normalised flat frame constructed by taking the
mean of several on sky images that contain very few stars (no stars at all would be pre-