";
print "ObjectMagnitude in V: ", $query->textfield(-name=>'vmag', -size=>5, -maxlength=>5, -default=>'12'); print "spectral type: ", $query->popup_menu(-name=>'spec', -values=>['O', 'B', 'A', 'F', 'G', 'K', 'M'], -default=>['A']); print " reddening E(B-V): ", $query->textfield(-name=>'ebv', -size=>5, -maxlength=>5, -default=>'0.0'); print " | ";
print "Observing conditions"; print "Moon brightness: ", $query->popup_menu(-name=>'moon', -values=>['bright', 'grey', 'dark'], -default=>'grey'); print "seeing (arcsec): ", $query->textfield(-name=>'seeing', -size=>4, -maxlength=>4, -default=>'1.5'); print " airmass: ", $query->textfield(-name=>'airmass', -size=>4, -maxlength=>4, -default=>'1.5'); print " Temperature (centigrade): ", $query->textfield(-name=>'Temp', -size=>4, -maxlength=>4, -default=>'15'); print " atmospheric pressure (hPa): ", $query->textfield(-name=>'atmpres', -size=>4, -maxlength=>4, -default=>'773'); print " relative humidity (percent): ", $query->textfield(-name=>'humid', -size=>3, -maxlength=>3, -default=>'25'); print " | ";
print "CCD"; print "readout noise (electrons): ", $query->textfield(-name=>'RON', -size=>3, -maxlength=>3, # FDR -default=>'3'); -default=>'3.5'); print "dark current (electrons/hour/pixel): ", $query->textfield(-name=>'DRK', -size=>3, -maxlength=>3, # FDR -default=>'4'); # CommI/II -default=>'13'); -default=>'1.5'); print " full well capacity (electrons): ", $query->textfield(-name=>'FWC', -size=>7, -maxlength=>7, # FDR -default=>'150000'); -default=>'130000'); print " |
";
print "ExposureExposure time (sec): ", $query->textfield(-name=>'obstime', -size=>5, -maxlength=>5, -default=>'3600'); print "Number of fibers: ", $query->radio_group(-name=>'nfiber', -values=>[' 1', ' 2'], -default=>' 2'); print " | Telescope"; print "mirror diameter (cm): ", $query->textfield(-name=>'mirrorD', -size=>4, -maxlength=>4, -default=>'220'); print "telescope efficiency: ", $query->textfield(-name=>'teleff', -size=>4, -maxlength=>4, -default=>'0.6'); print " |
The default values have been updated in Feb. 2004 to the configuration at the 2.2m telescope. A copy of the code can be obtained here.
The calculator computes the S/N per pixel (1 resolution element = 2.2 pixels) for a given exposure time.
Calculations are based on measured performances during the FEROS Commissioning.
ENDHEAD } sub print_end { print <| "; print "Expected S/N per pixel in UBVRI | |
| "; foreach $filter (@filters) { printf " | %s | ", $filter; } print "
Flux from sky (electrons/bin) Dark current (electrons/bin) Readout noise (electrons/bin) | ";
foreach $filter (@filters)
{
printf "%9.0f", $flux{$filter};
printf " %9.0f", $sky{$filter}; printf " %9.0f", $npixel * $DRK * $obstime; printf " %9.0f | ", sqrt($npixel) * $RON;
}
print "
| Expected S/N (per pixel) | "; foreach $filter (@filters) { printf "%6.1f | ", $snr{$filter}; } print "Additional information | "; foreach $filter (@filters) { if ($PeakPixel{$filter} > $FWC) { $IsOverexposed = 1; } } if ($IsOverexposed == 1) { print "
| "; print "Warning: The CCD is overexposed. The amount of charge collected in some pixels exceeds the full well capacity of the CCD. The charge from this pixels will bloom into neighbouring pixels in the same row and render the exposure almost unusable. Select a shorter exposure time."; print " | |
| "; print "Warning: The observing time is in the same order of magnitude as the shutter opening time. This means, the center of your CCD will be exposed for a significantly longer time than the edges of your CCD. This may result in poor flatfileding. If possible, then use a longer exposure time."; print " | |
| "; printf "The slit losses due to the seeing are %4.1f percent.", 100.*(1.-$seeingeff); print " | |
| "; if ($HitPixelFraction > 10.0) { printf "Warning: %4.1f percent of your CCD pixels (%4.1f percent of your wavelength bins) are hit by cosmic rays. This means, your optimum extraction algorithm may have trouble masking the pixels, that were hit by cosmic rays. If possible, then use a shorter exposure time.", $HitPixelFraction, $HitBinFraction; } else { printf "%4.1f percent of your CCD pixels (%4.1f percent of your wavelength bins) are hit by cosmic rays.", $HitPixelFraction, $HitBinFraction; } print " | |
| ";
if ($deltar >= 2.0 * $FiberRadius)
{
printf "Warning: More than 50 percent of the flux in the extreme wavelengths
is lost due to differential atmospheric refraction. "; } printf "atmospheric refraction: %4.1f arcsec at lambda = %4.0f Angstrom, %4.1f arcsec at lambda = %4.0f Angstrom ", $r1, $lambda1, $r2, $lambda2; printf "length of spectrum = %4.1f arcsec, fiber diameter = %4.1f arcsec ", $deltar, 2.0 * $FiberRadius; print " |
"; } #======================================================================= sub atmospheric_refraction { local($R); $z0 = atan2(sqrt(($_[0])**2-1),1); $sig = 1e4/$_[1]; $T = 273.15+$t; $x = log (($rh + 0.01)/ 100.0); $td = 238.3 * (($t + 238.3) * $x + 17.2694 * $t) / (($t + 238.3) * (17.2694 - $x) - 17.2694 * $t); $pw = 4.50874 + 0.341724 * $td + 0.0106778 * $td**2 + 0.184889E-3 * $td**3 + 0.238294E-5 * $td**4 + 0.203447E-7 * $td**5; $Pw = 1.333224 * $pw; $Ps = $ps-$Pw; $beta = 0.001254*(273.15+$t)/273.15; $kappa = 1.0; # spherical Earth $Ds = (1.+$Ps*(57.90e-8 - 9.3250e-4/$T + 0.25844/$T**2))*$Ps/$T; $Dw = (1.+$Pw*(1.+3.7e-4*$Pw)*(-2.37321e-3+2.23366/$T-710.792/$T**2+7.75141e4/$T**3))*$Pw/$T; $n0 = 1.+1.e-8*((2371.34+683939.7/(130.-$sig**2)+4547.3/(38.9-$sig**2))*$Ds+(6487.31+58.058*$sig**2-0.71150*$sig**4+0.08851*$sig**6)*$Dw); $gamma = $n0-1.; $R = $kappa*$gamma*(1.-$beta)*&tan($z0)-$kappa*$gamma*($beta-$gamma/2.)*(&tan($z0))**3; 180./3.14159*3600*$R; } sub tan { sin($_[0])/cos($_[0]); }