LBC: The Large Binocular Camera

*This page is out-of-date (August 2012)*.

An up-to-date description of the LBCs can be found here

Overview

The Large Binocular Cameras (LBC) are wide-field prime-focus imagers covering a field of view of about 23 x 25 arcmin. LBC-Blue is optimized to work in the UBV bands from 320 to 500nm. LBC-Red is optimized to work in the RIz bands from 500 to 1000nm.


Reference Paper/Information

Giallongo et al. 2006 (in preparation).

Contact E. Giallongo for information regarding the status of this paper. The instrument team requests that any paper using data from the LBCs contain the following acknowledgement:

insert suggested acknowledgement here

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General Specifications (Blue & Red Cameras)

Parameter Blue Camera Red Camera
Detector Type EEV CCD42-90 2048x4608 pixel, thinned, UV-coated EEV CCD42-90 2048x4608 pixel, thick, IR-coated
Pixel Size (microns) 13.5 13.5
Image Scale (arcsec/pixel) 0.23 0.23
Bias (DN) [CCDs: 1/2/3/4] 720 / 715 / 845 / 780 ?
Readout Time (seconds) 30 30
Gain (electrons/DN) [CCDs: 1/2/3/4] 1.75 / 1.75 / 1.75 / 1.75 ?
Read Noise (e-) [CCDs: 1/2/3/4] ~12 / ~12 / ~12 / ~12 ?
Saturation (DN) [CCDs: 1/2/3/4] 65536 / 65536 / 65536 / 65536 ?

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Filters for the Large Binocular Cameras

Filter Name Central Wavelength FWHM Tpeak cut on cut off Thickness Status
(nm) (nm) (%) (nm) (nm) (mm)
Blue Camera (space for 8 mounted in LBC-Blue)
U-BESSEL 364 ... 62 ... ... ... in LBC-Blue
B-BESSEL 420 ... 64 ... ... ... in LBC-Blue
V-BESSEL 527 ... 93 ... ... ... in LBC-Blue
SDT_Uspec ... ... ... ... ... ... in LBC-Blue
SDSS u' ... ... ... ... ... ... order deferred
g-SLOAN ... ... 94 ... ... ... in LBC-Blue
r-SLOAN ... ... 95 ... ... ... in LBC-Blue
Red Camera (space for 8 mounted in LBC-Red)
R-BESSEL ... ... ... ... ... ... ...
modified I-BESSEL ... ... 97.6 ... ... ... ...
r-SLOAN 629.4(5) 145.2(5) 98.7 ... ... 8.7(6) ...
i-SLOAN 770.5(5) 122.9(5) 96.6 ... ... 9.2(6) ...
z-SLOAN -(7) 146.6(5) 96.9 ... -(7) 9.0(6) ...
Y (4) 1044.6(5) 162(5) 96.6 ... ... 9.4(6) ...

Notes:
(1) The Bessel UBV filters listed here are identical to standard astronomical Johnson UBV filters.
(2) Click on the filter name to see the transmission curve (plot and ascii table of lambda [nm] vs transmissivity (%)
(3) Transmission curves for all filters currently in LBC-Blue (UBVg'r')
(4) The Y filter is a PI filter; please contact Xiaohui Fan (fan@as.arizona.edu) for availability.
(5) Central wavelengths are from the transmission curves measured through a collimated beam and are averages of the 50% cut-on and 50% cut-off wavelengths. In a convergent f/1.45 beam, the filter transmissivity is shifted to the blue by 6-10 nm where the shift is greater for longer wavelengths. Consequently, the filter FWHM as measured in a convergent beam would be slightly greater than the value reported in the table above.
(6) Filter thicknesses are averages of several measurements made at positions along the edge, the outer few millimeters of each filter. Reported in email from Ray Bertram dated October 1, 2007.
(7) The Sloan z' filter has no red cutoff.
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Detector Quantum Efficiencies

lbc_qe.jpg

CCD sn 350 nm 400 nm 500 nm 650 nm 900 nm 1000 nm
Blue Channel Arrays
8341-16-3 [CCD 1] 53.8 81.3 85.4 78.8 28.3 -
8351-18-4 [CCD 2] 56.1 83.7 88.2 80.1 27.3 -
9283-4-5 [CCD 3] 53.8 81.1 83.8 76.8 27.4 -
9283-1-4 [CCD 4] 56.3 77.7 80.5 75.0 28.3 -
Red Channel Arrays
9434-17-3 [CCD 1] - - 95.1 96.7 57.0 13.2
9434-16-5 [CCD 2] - - 82.8 90.2 53.2 11.8
9434-15-3 [CCD 3] - - 84.3 90.6 51.5 11.2
9434-15-4 [CCD 4] - - 87.4 95.7 54.4 12.2

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#Sensitivity

Sensitivity

Please check the LBC Blue commissioning webpage for the latest news. The LBC team has reduced commissioning data from fall 2006 and is also working on data from the SDT runs in winter/spring 2007 to determine accurate zeropoints and color terms. Note that baffling to reduce scattered light which contributed to the sky background has been added since the beginning of 2007; this will change the flat field but we think produced little or no vignetting around the edges of the field.
  • 2007-02-15 UT: temporary baffle (black paper annulus) placed on inner, flat edge of L2.
  • 2007-02-20 UT: sturdier baffle replaced temporary one; better centered.
  • 2007-05-xx: plans to blacken the accessible lens inner edges before May SDT.

Filter1 Zero Point2 Sky3 PtSrc Det4 SurfBr Lim5 BL Time6
* *(magnitude) (mag/arcsec2) (magnitude) (mag/arcsec2) (seconds)
LBC-Blue
U-Bessel
B-Bessel
V-Bessel
LBC-Red
R
I
z'

1 Filters correspond to the entries in the filter table.

2 The Zero Point (ZP) is derived from the counts per second from a star with a known magnitude (e.g. a standard star). Calibrations of real data, when the ZP is known, would then be: magnitude = ZP - 2.5*log10(counts/second)

3 The surface brightness of the sky, in magnitudes per square arcseconds, given for both the dark sky (no moon) and full moon (100% illuminated) extremes. The Exposure Time Calculator (ETC) can calculate point source or surface brightness limits at specific phases of the moon.

4 The point source detection limit, given as a 5σ detection in a 1 hour exposure, within an aperture scaled to a "standard" seeing of FWHM=0.6 arcseconds. For different seeing, use an aperture equal to twice the FWHM of the seeing.

5 The surface brightness limit derived from the noise produced by the background photons, given as 1σ in a 1 hour exposure with 1 square arcsec of sky.

6 Time (seconds) to reach the background limit. This is defined as the time when the instrumental sources of noise (readnoise, pickup) is equal to the square root of the number of photoelectrons. Note that it is better to be safely beyond this point of equality, so you should actually integrate 2-3 times as long as this.

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LBC Focal Plane Layout

The LBC focal plane consists of four EEV42-90 CCDs (2048 x 4608 pixels, 13.5 microns square) arranged such that three of the chips are butted along their long edges, with the fourth chip rotated 90 degrees and centered along the top of the other CCDs. The image below shows the relative positions of the arrays and their extent on the sky. The green circle indicates the apparent size of the full moon. Each CCD covers approximately 7.8 x 17.6 arcmin, with gaps between the chips of ~18 arcseconds (70 pixels). The CCDs are numbered clockwise from lower right (1), to bottom center (2), to lower left (3), to the top rotated CCD (4). There is also an engineering drawing of the focal plane (rotated 90 degrees clockwise from the previous image), pulled from the instrument team's documentation. Click either image for a larger version.

Note that with spaces between the CCDs in two orthogonal directions, care must be taken in dithering to properly fill in the gaps when producing a deep mosaic image.

Attempting to get a thumbnail of the image that is clickable, taking you to a page with the full size image and a basic description...
see LbcLayoutImage and test

LBClayout.jpg LBClayout_eng.jpg

\xA9 LBTO -- DavidThompson - 24 Oct 2006
Topic revision: r27 - 22 Aug 2012, OlgaKuhn
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