MRS Exposure Calculator Help

Magnitude:

Enter magnitude at the given bandpass.

Effective Temperature

Enter the effective temperature of the source in Kelvin. Here is a table which may help: 
Type        B-V         Effective Temp
        V       III      V        III
O5    -0.32    -0.32   47000
B0    -0.30    -0.30   30500
B5    -0.16    -0.16   15000
A0     0.00     0.00    9500
A5     0.15     0.15    8300
F0     0.29     0.27    7300
F5     0.42     0.45    6600
G0     0.58     0.65    5900     5400
G5     0.69     0.84    5600     4800
K0     0.85     1.03    5100     4400
K5     1.16     1.45    4200     3600
M0     1.42     1.57    3700     3300
M5     1.61     1.80    3000     2700

Flux

Enter the flux in units of 10-19 ergs/cm2/s/A) at the wavelength of interest. Note the flux is in units of wavelength not frequency!

Sky Brightness:

Enter either the moon phase (Bright, Grey or Dark Time) or the sky brightness that you wish to include.

You may find the ESO Sun & Moon Tables to be helpful.

The Sky brightness calculations are made using the following data:
Days from
new moon 		Sky Brightness
U B V R I
0 22.0 22.7 21.8 20.9 19.9
3 21.5 22.4 21.7 20.8 19.9
7 19.9 21.6 21.4 20.6 19.7
10 18.5 20.7 20.7 20.3 19.5
14 17.0 19.5 20.0 19.9 19.2

Seeing:

Enter the seeing you may expect during your observations.

You may find the HET Image Quality Statistics to be helpful.

Input fibers of the MRS:

There are two sizes of fibers for use with the mrs: the 1.5 arcsecond fibers and 2.0 arcsecond fibers. Each fiber size has a blue sensitive and red sensitive option. Only the 1.5 arcsecond fibers have a sky fiber. The value is the inner diameter of the fiber projected on the sky. MRS spectrograph details

Wavelength:

Enter wavelength (IN ANGSTROMS) at which singnal-to-noise or time calculation is desired.

Exposure Time:

Total combined exposure time (IN SECONDS) for all exposures. Required if you are calculating the S/N for a given exposure time.

Desired S/N:

Enter desired Signal/noise ratio at given wavelength (PER BINNED PIXEL). Required if you are calculating the exposure time to reach a given S/N.
Back to the Exposure Time Calculator
Matthew Shetrone - shetrone@astro.as.utexas.edu