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Large Format Camera (LFC) Technical Specifications

View the original specsheet.


    Contents

  1. Camera parameters
  2. Field diagram and chip orientation
  3. CCD specs
  4. Filter specs
  5. Sensitivities
  6. Custom filters
  7. Updates

1. Camera Parameters

  • Mosaic of six 2048 × 4096 pixel SITe SI-002 thinned, backside illuminated, AR coated CCD located at Hale Telescope's prime focus (f/3.3)
  • Field diameter: 24′
  • Pixel size: 15 µm
  • Pixel scale:
    • 0.18″/pixel binned 1×1
    • 0.36″/pixel binned 2×2
  • Minimum exposure time: 0.6 sec
  • Gap between CCD chips: ~ 15″
  • Readout (mosaic) options:
Mode (mosaic command) Chip numbers used Binning value (pixels) Raster value Field size Readout/write
time (sec)
lfc / lfc2 0, 1, 2, 3, 4, 5 1 × 1 No raster 25.3′ × 24.8′ 115
lfc2bin 0, 1, 2, 3, 4, 5 2 × 2 No raster 25.3′ × 24.8′ 56
lfcfour 0, 1, 2, 3 (central 4)
 1 × 1 No raster 12.5′ × 24.8′ 111
lfczero 0 (chip 0) 1 × 1 No raster 6′ × 12.3′ 105
lfczerobin 0 (chip 0) 2 × 2 No raster 6′ × 12.3′ 45
lfcfind 0 (chip 0) 2 × 2 [0–1024 × 1024–2048] 6′ × 6′ 31
  • Image file size: ~ 17 Mb per CCD at 1 × 1 binning
  • LFC guider: partially vignetted 512 × 512 SITe chip located in the open area between chips 3 and 5. See focal plane schematic. Capable of guiding down to mV ~ 18

2. Field Diagram and Chip Orientation

North-South

N-S orientation.

East-West

E-W orientation.


3. CCD Specs

The six LFC CCDs are SITe SI-002 chips, 2048 wide by 4096 pixels tall. Each pixel is 15 microns square, which corresponds to ~ 0.18″/pixel (0.175″/pixel at the center of the mosaic; 0.185″/pixel at the field edge).

CCD # Bias (DN) Gain (e−/DN) Read noise (e−) Saturation (DN) [a] Linearity curves Normalized linearity
0 650 2.0 11 59100 jpeg, postscript mean, time
1 1700 1.9 9 53400 jpeg, postscript mean, time
2 1100 2.1 9 40800 jpeg, postscript mean, time
3 2600 2.0 8 44000 jpeg, postscript mean, time
4 1700 2.1 8 21700 jpeg, postscript mean, time
5 4100 1.8 6 61400 jpeg, postscript mean, time
[a] Largest DN value that still lies within 0.1% of the integral nonlinearity value.

4. Filter Specs

Filter wheel has slots for 4 filters.

Filter Central λ
(Å)		 Width
(Å)		 Thickness
(mm)		 Focus offset
(mm from r')		 Domeflats [b] Dark sky [b]
(raw chip 0)		 Transmission
r' 6255 1470 3.05 – 5 1400 data, plot
i' 7680 1540 3.05 – 3 650 data, plot
z' ~9000 ~1800 (w/qe) 3.05 – 5 750 data, plot
g' 4660 1400 8.02 +1.5 40   data, plot
u' 3540 590 8.38 +1.6 120 (highlamp)   data, plot
Rs 6930 1220 10.26 +2.0 8   data, plot
Is 8190 1670 10.26 +2.0 5   data, plot
B-bess 4400 1000 7.0 +1.3 2 (highlamp)   data, plot
V-bess 5500 900 7.0 +1.3 40   data, plot
R-bess 6300 1200 7.0 +1.3 10   data, plot
I-bess 9000 3000 7.0 +1.3   data, plot
Broad-RI 7670 2940 6.0       data, plot
Hα 6570 100 11.68 +2.8 120   plot
S-II 6730 90 11.68 +2.8 120   plot
6610/100 6610 100 7.06 +1.3 120   plot
6650/100 6650 100 7.06 +1.3 120   plot
6700/100 6700 100 6.93 +1.3 120   plot
5200/70 5200 70 4.90 ?     not yet on record
5085/70 5085 70 5.13 ?     not yet on record
[b] Seconds to 10,000 DN (unbinned)

5. Sensitivities

See also this page.

6. Custom Filters

LFC array focus maps.

  • 6.1 inches square
  • Thickness: ~3 mm (min); 10 mm (max), but < 6 mm preferred due to weight considerations.
  • Contact the Palomar support team about non-observatory filter mounting. Also see Rob Simcoe's LFC Page for more information.

7. Updates

MCDCOM program update (February 20, 2007)

  1. Added logic to filter wheel movement so that the filter wheel will correctly move to the requested position in both extreme cold and extreme hot ambient temperatures.
  2. Created two new backup MCDCOM programs in case the hot/cold logic fails:
    • mcdcom_hot to be used in hot temperatures
    • mcdcom_cold to be used in cold temperatures
  3. When mcdcom is started, 3 scripts are automatically copied to the user's working directory (if none exist):
    • focus_coarse
    • focus_fine
    • dither5
  4. A test version of the lfcguider (lfcguide_ns) is now available which attempts to guide at non-sidereal rates. Target rates are entered in the File/BlackBelt menu popup window.

MCDCOM program update (April 28, 2005)

  1. The iraf command now works. When toggled ON, files are written as signed integer FITS.
  2. The istat command now works correctly, displaying the mean of chip 0.
  3. A new command fs has been added. This adds a filename suffix (eg: .fits). To clear this at any time, issue fs "".
  4. New commands have been added to turn lamps on and off from the command line, useful in domeflat scripts:
    • telescope lowlamp
    • telescope highlamp
    • telescope arclamp
    • telescope lampsoff
  5. Fixed the header bug in the guider program. All fits files should now have proper telescope header information, regardless of when a go is issued.

Added narrow band filters (Nov. 2007)

Karl Stapelfeldt has supplied two new narrow band filters from Asahi Spectra. The filter plots are linked above, and are named H-alpha and S-II.

More narrow band filters (2008 & 2009)

Ted Wyder and Brian Siana have added the following filters which are listed and linked above: 6610/100,6650/100,6700/100,3800/200. All are available to the public.

Questions? We've answered many common observing and operations questions in our observer FAQ page.
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LFC Specs / v 2.0.3
Last updated: 28 March 2015 ACM/AFB

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