signal_cirsi is modified version of the program
signal
written by Chris Benn.
How to get the Fortran source
If the WWW version is sufficient for your purposes, the Fortran source
code or the binary may be of more practical value.
The fortran source resides in
~rgm/soft/signal/signal_cirsi.f
Hardware Version
The CIRSI hardware has gone through a number of changes between
observing runs:
Telescope and Focus | Diameter (m) | um/" | "/pixel | fov (single array) |
Contiguous field for 4 exposures |
Exposures per degree |
---|---|---|---|---|---|---|
WHT Prime f/2.8 |
4.2m | 57.0 | 0.32 | 5.5' x 5.5' | 20.9' x 20.9' | 30.9 |
INT Prime f/3.3 |
2.5m | 40.49 | 0.46 | 7.80' x 7.80' | 29.6' x 29.6' | 16.4 |
OCIW DuPont Cass f/7.5 | 2.5m | 92.6 | 0.20 | 3.4' x 3.4' | 13.0' x 13.0' | 85.2 |
The current version of signal_cirsi uses the H band throughput and sky background estimates measured at the INT on May 6th 1998.
CIRSI Measured Zero Point Information | ||||
Telescope and Focus | Date | measured or predicted | Waveband | Zeropoint |
---|---|---|---|---|
WHT Prime | June 98 | measured | H | 2.9e09 |
INT Prime | May 98 | measured | H | 0.9e09 |
CIRSI Predicted Zero Point Information | ||||
Telescope and Focus | Date | measured or predicted | Waveband | Zeropoint |
---|---|---|---|---|
WHT Prime | Sep 98 | predicted | z | 1.1e10 |
" | Sep 98 | predicted | J | 8.5e09 |
" | Sep 98 | predicted | H | 5.0e09 |
INT Prime | Sep 98 | predicted | z | 4.7e09 |
" | Sep 98 | predicted | J | 2.9e09 |
" | Sep 98 | predicted | H | 1.5e09 |
DuPont Cass | Sep 98 | predicted | J | 3.7e09 |
Sep 98 | predicted | H | 2.2e09 | |
Sep 98 | predicted | Ks | 1.3e09 |
The airmass can be computed from the Skycalc page: http://imagiware.com/astro/airmass.html .
The seeing parameter is given in arcseconds and corresponds to the full-width at half-maximum of the seeing disk.
The values currently set in the simulation are the following:
Broad Band Filter Sky magnitude (mag/arcsec**2) z 18.8 (from LaPalma) J 16.0 (from ESO) H 14.0 " Ks 12.5 "
Note:
Sky brightness can vary substantially during the night and with season.
Filter
At the INT and WHT CIRSI does not function usefully longward of
the H band, and this can only be used in the wavelength range
0.9 to 1.8 microns (z to H). At the Dupont, Ks will be available
be z shall not.
CIRSI has a large selection of broad and narrow band filters.
The filter response curves and specifications are
here
Exposure Time
Do not confuse exposure time and total observation time, the
latter being a sum of exposure time and overheads in
the telescope and instrument. Further information on this
will follow. On the WHT and INT, assume 50% unless told otherwise.
Example Output
Note: These examples are are based on early estimates of the
CIRSI system throughput when non-optimum blocking filters were
in use.
I Instrument = INT CIRSI U Tel. geometric area (sq.m) 4.41
G Grating none Telescope/instr. throughput 0.14
D Detector CIRSI Detector efficiency 0.60
B Band H Pixel size (microns) 18.5
M Apparent magnitude 0.0 Readout noise (electrons) 40.0
P mag (0) or mag/arcsec**2 (1) 0 Photons/s/A/sq.cm mag=0 92
T Integration time (sec) 1.0 W Effective bandwidth (A) 2300.00
F FWHM (object*seeing) 1.0 Empirical/theoretical 1.0
S Slit width (arcsec) 0.0 K Sky brightness mag/sq.arcsec 14.00
A Airmass 1.0 E Extinction per airmass (mag) 0.11
Detected photons from object = 8.08943E+08
Detected photons/pixel from sky = 423.939
Detected photons/arcsec from sky = 2031.97
Detected photons from sky in aperture with diameter 2*FWHM = 6383.63
Signal-to-noise 8.08943E+08/ 28442.5 = 28441.4
Scale in X direction: 0.46 "/pixel; 1024 pixels = 467.73 "
Scale in Y direction: 0.46 "/pixel; 1024 pixels = 467.73 "
CIRSI gain =25.0 e-/ADU approx.; readnoise = 40 electrons
I Instrument = INT CIRSI U Tel. geometric area (sq.m) 4.41
G Grating none Telescope/instr. throughput 0.14
D Detector CIRSI Detector efficiency 0.60
B Band H Pixel size (microns) 18.5
M Apparent magnitude 19.0 Readout noise (electrons) 40.0
P mag (0) or mag/arcsec**2 (1) 0 Photons/s/A/sq.cm mag=0 92
T Integration time (sec) 300.0 W Effective bandwidth (A) 2300.00
F FWHM (object*seeing) 1.0 Empirical/theoretical 1.0
S Slit width (arcsec) 0.0 K Sky brightness mag/sq.arcsec 14.00
A Airmass 1.0 E Extinction per airmass (mag) 0.11
Detected photons from object = 6095.92
Detected photons/pixel from sky = 127182.
Detected photons/arcsec from sky = 609592.
Detected photons from sky in aperture with diameter 2*FWHM = 1.91509E+06
Signal-to-noise 6095.92/ 1394.73 = 4.37068
Scale in X direction: 0.46 "/pixel; 1024 pixels = 467.73 "
Scale in Y direction: 0.46 "/pixel; 1024 pixels = 467.73 "
CIRSI gain =25.0 e-/ADU approx.; readnoise = 40 electrons
I Instrument = INT CIRSI U Tel. geometric area (sq.m) 4.41
G Grating none Telescope/instr. throughput 0.14
D Detector CIRSI Detector efficiency 0.60
B Band H Pixel size (microns) 18.5
M Apparent magnitude 19.9 Readout noise (electrons) 40.0
P mag (0) or mag/arcsec**2 (1) 0 Photons/s/A/sq.cm mag=0 92
T Integration time (sec) 300.0 W Effective bandwidth (A) 2300.00
F FWHM (object*seeing) 1.0 Empirical/theoretical 1.0
S Slit width (arcsec) 0.0 K Sky brightness mag/sq.arcsec 14.00
A Airmass 1.0 E Extinction per airmass (mag) 0.11
Detected photons from object = 2660.97
Detected photons/pixel from sky = 127182.
Detected photons/arcsec from sky = 609592.
Detected photons from sky in aperture with diameter 2*FWHM = 1.91509E+06
Signal-to-noise 2660.97/ 1393.50 = 1.90956
Scale in X direction: 0.46 "/pixel; 1024 pixels = 467.73 "
Scale in Y direction: 0.46 "/pixel; 1024 pixels = 467.73 "
CIRSI gain =25.0 e-/ADU approx.; readnoise = 40 electrons
I Instrument = WHT CIRSI U Tel. geometric area (sq.m) 12.47
G Grating none Telescope/instr. throughput 0.09
D Detector CIRSI Detector efficiency 0.60
B Band H Pixel size (microns) 18.5
M Apparent magnitude 21.5 Readout noise (electrons) 40.0
P mag (0) or mag/arcsec**2 (1) 0 Photons/s/A/sq.cm mag=0 92
T Integration time (sec) 5000.0 W Effective bandwidth (A) 2300.00
F FWHM (object*seeing) 1.0 Empirical/theoretical 1.0
S Slit width (arcsec) 0.0 K Sky brightness mag/sq.arcsec 14.00
A Airmass 1.0 E Extinction per airmass (mag) 0.11
Detected photons from object = 17759.5
Detected photons/pixel from sky = 1.86997E+06
Detected photons/arcsec from sky = 1.77596E+07
Detected photons from sky in aperture with diameter 2*FWHM = 5.57933E+07
Signal-to-noise 17759.5/ 7473.87 = 2.37622
Scale in X direction: 0.32 "/pixel; 1024 pixels = 332.28 "
Scale in Y direction: 0.32 "/pixel; 1024 pixels = 332.28 "
CIRSI gain =25.0 e-/ADU approx.; readnoise = 40 electrons