KAOS Exposure Time Calculator

Online help for the IRAF SPECTIME package

Set the integration time to INDEF or leave it blank if you wish to compute the total exposure time needed to achieve the desired signal-to-noise per pixel at the wavelength specified below. If you set the integration time to some value a new signal-to-noise per pixel will be computed for that time, ignoring what is in the signal-to-noise ratio box.

Exposure time (s):			Max time per exposure (s):			S/N ratio:
Wavelength (A):			Seeing (arcsecs):			Airmass:

Select a spectrograph configuration. Note that the spectrograph model parameter combines various elements. For the low resolution model the optics, grating, and detector are included while for the high resolution the optics and detector are included but not the grating or order blocking filter. A single constant throughput value may be set for these elements. Instead of describing gratings by their ruling parameters a generic blaze wavelength and dispersion are specified. A blaze function is not modeled though it is included in the throughput for the low resolution model.

The 30 meter fibers can only be used with Subaru. The ratio of the collimator and camera focal lengths define the scale change from the telescope focal plane scale to detector.

Spectrograph:	Low Res - SDSS + VPH Grating + LBNL CCD Echelle optics - without grating and filter

Telescope:	Gemini Subaru		Fibers:	FBP60m FBP30m (Subaru)
Blaze wavelength (A):			Dispersion (A/pixel):
Grating throughput:			Filter throughput:
Collimator FL (m):			Camera FL (m):

Select the source and sky spectra with the following parameters. There are different parameters for each type of source.

Source:	E_galaxy Sb_galaxy Sc_galaxy Im_galaxy Protgalaxy G0V_HD141004 K0III_HD136512 blackbody flambda_power fnu_power	Sky:	UVES @ 0.2A/pixel

Galaxy and Star Parameters:

The magnitude is the integrated flux through a V filter (in the observed frame) and through the spectroscopic aperture.

Magnitude (V):					Redshift:

Blackbody and Power Law Parameters:

The power law index is only used if the source type is set to Flambda_power or Fnu_power. Setting the power law index to 0 is equivalent to a flat spectrum for that particular power law function. If the value of the wavelength of the source flux is set to INDEF then the central wavelength value above is used. The entry for the wavelength of the source flux is ignored for broadband source fluxes.

Temperature (K):			Power law index:

Flux/mag:			Units:	AB mag F_lambda F_nu U B V R I		Wavelength (µm):

Three graphs are produced in addition to the text. These are functions of wavelength over the approximate wavelength range covered by the detector. The first two graphs are always the same and one additional graph may be specified below. The standard graphs are the sky subtracted object counts in data numbers and the signal-to-noise ratio in the sky subtracted object.

Select:	Thruput from telescope to detected photons Object, sky, and total counts per exposure Object and background count rates per exposure Spectrograph model transmission Telescope transmission Corrector transmission Fiber transmission