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WHTWFC Mosaic with Ultradas + SDSU Gen.2

NB these figures refer to WHTWFC when it was used with a Gen. 2 controller. Converted to Gen. 3 on the 1st June 2007

Device Identification

Mosaic name WHTWFC
Year of manufacture 1999
Serial numbers CCD1  7461-14-6 
CCD2  7461-11-6
First Light on La Palma Initial commissioning by Simon Tulloch November 1999
Description The camera contains two EEV-42-80 thinned and AR coated CCDs butted along their long axis to provide a 4K × 4K pixel mosaic.

For further mechanical and defect information regarding these devices see ING Technical note 119 The 2 Chip EEV Mosaic by S.Tulloch. The electronic information in technical note 119 refers to the Dutch controller and is superseded by the information on this page.

Operational Characteristics

Readout Speed
Gain (e/ADU)
Noise (e)

Noise (ADU)

Bias (ADU)
Linearity (ADU)
Chip 1
High speed (45 s)
Chip 2
Chip 1
Low speed (58 s)
Chip 2


When windowing the mosaic is considered a single large chip measuring 4308 x 4200 pixels.


All binning modes have been tested up to 5 × 3 with no increase in noise.


Please read notes on linearity measurement at ING, all measurements made 4th June 2001. Also available in tabulated form.


Physical Characteristics

Pixel Size 13.5 microns x 13.5 microns
X size of digitised area in pixels (each ccd) 2154
Y size of digitised area in pixels (each ccd) 4200
X size of useful imaging area ( each ccd ) 2048
Y size of useful imaging area ( each ccd ) 4100
X start of useful imaging area ( each ccd ) 53
Y start of useful imaging area ( each ccd ) 1
LN2 capacity of cryostat 2.5 litres

Mosaic coplanarity and spacing.

The coplanarity and relative positions of the two chips was measured using the RGO flatness scanner. Each chip was flat to within the resolution of the flatness scanner, which in this case was about 5mm.

Chip butting was done with the aid of 50mm PTFE shims that were removed after the chips were securely bolted to the base plate. The gap between active Silicon on either side of the join is approximately 39 pixels.

Mosaic alignment with cryostat

The orientation of the chips in the cryostat is orthogonal to a normal EEV 42-80 camera ; the long axis is parallel to the primary dispersion axis when used at UES on the William Herschel telescope.

The cryostat window had a thickness of 5mm. The distance from the front face of the window to the surface of the CCD was measured using a travelling microscope.

Operational Parameters

Operating temperature 153K
Preferred amplifier CCD1 - RHS, 
Anti blooming -

Measured Characteristics

Dark Current ( @-120C )

        CCD1  No measurable dark current.
        CCD2  No measurable dark current.

See 900 second Dark frame chip1 is on the right.

Cosmic Ray count      ~2000 counts/chip/hour at sea-level.

Full Well Bloom Limit

        CCD1  170000 electrons.
        CCD2  210000 electrons.

Charge Transfer Efficiency

Low level corresponds to a signal charge of 1600 electrons, High level to a signal level of 100,000 electrons.
CCD1 VCTE Lo-level VCTE Hi-level HCTE Lo-level HCTE Hi-level
Left Output 0.999998 0.999997 0.999997 0.999998
Right Output 0.999998 0.999997 0.999997 0.999998

CCD2 VCTE Lo-level
HCTE Lo-level
Left Output >0.999999
Right Output


Fringing. The graph below shows fringing with WHTWFC as measured on UES.

Pretty Pictures

Horse Head Nebula

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Last modified: 21 November 2010