Availability of NAOJ 8k x 5k pixel Mosaic CCD Camera on WHT
Announcement of Opportunity for Semester 98A
The Mosaic CCD group (NAO Japan and University of Tokyo) under the
auspices of the Japan-UK Ground-Based Board invites
proposals for wide-field imaging observations with the NAOJ 5000 x
8000 pixel mosaic CCD camera at the William Herschel Telescope in the
Spring semester 1998. The mosaic CCD camera (MCCD) is the one of
largest cameras available to the astronomical community today. The
camera uses 40 of 1K x 1K pixel unthinned CCDs made by TI-Japan. The
5 x 8 array has 90\% gaps between each row and column of CCD
chip. Thus a sequence of 4 images are required to image a contiguous
field. At the WHT prime focus, it can observe a 32.4 arcmin x 50.7
arcmin field with four shifted exposures with a pixel size of 0.2
Recent scientific results from a 4000 x 7000 camera are described in
Kashikawa et al (1995,ApJ Letters, 452, 99) . See also a paper (Sekiguchi et
al, 1992, PASP, 104 ,744) describing a 2000 x 8144 early version of the
camera system. Recent results obtained with the WHT in April 1996
are shown at
and links therein.
How to Apply
MCCD is a private instrument and owned and supported by the Mosaic CCD
Group. Proposals are invited to use the MCCD for the forthcoming PATT
deadline. It is envisaged that the camera may also be made available
in semester 98B.
Applications should be made through PATT in the normal way.
Applicants should contact the UK-MCCD Project Scientist, Dr Richard
or visit the WWW page
if they require any further
information. Consultation with the UK Project Scientist
prior to submission is welcome but is not a prerequisite. After
submission the Tokyo MCCD team will technically assess all
submitted proposals. In addition the Japan-UK Ground-Based
Board may identify relevant Japanese collaborators for the
Instrument Specifications and Sensitivities
The mosaic CCD camera can be used for wide-field imaging observations at the
WHT prime focus and is very well suited for observations of cluster of
galaxies or any kind of surveys. The instrument was used at the WHT prime
focus in Spring of 1996 for about 10 nights and worked well.
The instrument specifications are listed below:
CCDs are organized in 5 x 8 array with 90\% gaps in between. Four
exposures are required to complete a contiguous field by filling the gaps.
Each CCD has 1K x 1K of 12 micron pixels.
Spatial pixel scale 12micron pixels -- 0.20 arcsec at WHT Prime Focus.
Available color filters: The MCCD needs dedicated large 25cm x 25cm
filters. Currently Johnson B, V, R, and I are available as well as narrow I
(710nm to 830nm) and Z (830nm to 1100 nm). Other color filters including
narrow band filters can be manufactured. The typical cost of such filters,
if manufactured by an experienced Japanese company, is around US$ 10,000.
The quantum efficiency of the CCD is about 20% at 400nm, 35% at
500nm, 50% at 600-700nm, 40% at 800nm and 15% at 900nm. See WWW site
for a figure showing the spectral response of CCD convolved with + B,
V, R, narrow I and Z filters.
The limiting magnitude (magnitude that can be used for useful image
classification ie s/n=25) is approximately 24 mag in B with 30 minutes
exposure and 23 mag in V band with 30 minutes exposure based on the
preliminary data analysis of 1996 spring data. Add two magnitudes to
get the s/n 5 detection limits for 1arcsec seeing and a 1" radius
The readout time of whole array is 110 seconds. The entire frame data are
stored in local memory and the next exposure can start immediately after the
readout out. The amount of the data for one exposure is 80M byte. The camera
is remotely controlled by SPARCstation2 which typically takes 3 minutes to
transfer the 80M-byte data to its hard disk. It is not possible to take
exposures in cycle shorter than 3 minutes because of this data-transfer.
The image data from each CCD is saved as an IRAF binary file. Typical
amount of one night data ranges from 2Gbyte to 4Gbyte.
A suite of IRAF scripts and fortran programs have been developed to
reduce and astrometrically calibrate the MCCD dataset by the UK-MCCD
team. These will be made available to anyone who uses the camera.
Published by Richard G. McMahon
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge
Last modified: Mon Sep 15 18:19:47 1997