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This page describes the detectors characteristics of EMMI. Concerning the new Red CCD, the commissioning page is still available.
This page is based on the updated EMMI manual and the commissioning page.

Table of Content

	Introduction + CCD characteristics
	Detectors Orientation
	Bias, RON, Gain, Shutter Delay and Linearity.
	Red CCD: the gap and the FOV
	Red CCD: read-out modes and binning modes
	Quantum efficiencies
	Hints and Tips for new Red CCD. Be sure to read this!

Introduction

EMMI works with three thin, back-illuminated, AR coated scientific CCD cameras; two of them, which are arranged in a mosaic, in the red arm and one in the blue arm. The red CCD was upgraded in May 2002 with two new CCD chips, nicknamed Zeus (master chip) and Michele (slave chip) and a new FIERA controller. The following tables summarizes the CCDs characteristics.

Red CCD

Blue CCD

Detectors Orientation

In the orientation of the images of the different detectors in the RTD (Real-Time Display) (as shown above), the North is parallel to the rows or to the columns of the CCDs. The default rotator offset angle is 0, and the chip orientation is also indicated at the bottom of the RTD in the control room. The orientation can be changed by applying an offset to the rotator of EMMI.

Bias, RON, Gain, Shutter Delay and Linearity

The values of the bias, the read-out noise, the shutter delay and linearity are constantly updated and can be found in the CCD page.

That page also links to the evolution of the various parameters with time.

Note that for the Red CCD, the mosaic is read in four output modes via four separate amplifiers, two for each CCD chip, giving slightly different values for the bias level, gain and read-out noise.

Red CCD: the gap and the FOV

The two chips of the Red CCD are mounted side-by-side, with an overscan gap in between. The gap width is 47 pixel (in the x direction), i.e. 7.82''. The following figure illustrates this, as well as the field-of-view of the CCD.

Note that windowing is not possible with the Red CCD (to the contrary of the Blue CCD).

Red CCD: read-out modes and binning modes

Three read-out modes are available for the Red CCD: slow (100 Kps), which has the lower read-out noise and it is advisable to use it for spectroscopy of faint targets. There is the normal read-out mode (255 Kps), which is an all purpose mode. Finally, the fast read-out mode (625 Kps); which is suitable only for acquisition, tests and so on.

Only binning 1 x 1 (0.166 ''/pix) and 2 x 2 (0.33''/pix) are currently offered, the former being recommended to avoid undersampling problems.

Quantum efficiencies

The following figures show the quantum efficiencies of the two CCDs.

Red CCD.

Blue CCD

• The FITS frames produced by the new EMMI-Red CCD are written as "multiple extention FITS file". In the modes offered, the images come in 4 extensions corresponding to the 2x2 amplifiers.A small MIDAS procedure is available to read-in new EMMI red frames and paste the pieces together. ]
• Header: most of the generic keywords are in the first FITS extension, which contains no data. The following 4 extensions (which contain one image each) list the keywords related to each chip.
• The read-out speed is in HIERARCH_ESO_DET_READ_CLOCK, where it is listed in kps (625=fast, 225=normal, 100=slow). The read speed is listed are normal in all modes.

• While windowing can still be defined, it is ignored by the instrument.
• While other combinations are valid in P2PP, the only binning allowed are 1x1 and 2x2.
• The spectral dispersion used to be along x, it is now along y (does not matter at the level of OB definition).

2003-10-19 oh