FCU imaging ETC

FCU Imaging ETC

ETC Version 0.1

This form will calculate the count rates and S/N ratio for a simulated spectrum of ONE source in an FCU imaging observation.

For general help on how to use this Exposure Time Calculator or for help on various topics, click on the appropriate highlighted words.
Please read the current release notes before submitting any ETC requests.

Question 0. Select one response show method:

a) Update this page Open new tab
b) Go to White Page Mode

Question 1. Select one Camera and the Filter(s):

Detector	Filter Wheel 1	Filter Wheel 2	Filter Wheel 3
UVO
NUV
FUV

Question 2. Specify the exposure parameters:

Exposure time needed to obtain a S/N ratio of
S/N ratio reached in an exposure time of seconds.

Select the source type and photometric extraction aperture (centered on the target) that will be used for the S/N ratio calculation:

Point Source
	Use the default region for the camera selected, a circular region containing 80 percent of total light.
	Use a square region of size:
	Use a circular region of radius (arcsec):
	Use a circular region of radius (arcsec):
	Use a circular region containing percent of total light. The range of supported values for this option is limited. The limits are determined by the PSF and target spectrum.
Extended Source
	Use a square extraction region of size (pixels):
	Use a circular region of radius (arcsec):
	Use an arbitrarily sized circular region of radius (arcsec):

Question 3. Choose one of the following spectral distributions for the target:

Note: for User supplied and uploaded spectrum, please use only FITS or text (DAT) format files.
	Upload Spectrum File:
	Castelli and Kurucz Models:	[Sp Teff log(g) log(z)=0]
	Pickles Models:	(Sp Teff)
	Kurucz Models:	[Sp Teff log(g) log(z)]
	Hubble Standard Star spectra:
	Non-Stellar Objects:
	a Black-body with temperature	T =
	a Power-law:	F(λ) = λ **
	a Flat continuum in
	No continuum. If selected, at least one emission line must be specified below; the reference wavelength from part 2 above must correspond to one of the lines.

Specify the extinction E(B-V) =

Extinction applied normalization.

Specify the redshift z =

Add emission lines to the input spectrum (optional): Note: emission lines are added *after* the spectrum has had renormalization applied, but not extinction and redshift applied.

Line Center	FWHM	Integrated Flux
Å	Å	(erg/cm²/s)
(vacuum)

Note: integrated flux units are per arcsec² for extended sources. All three of the parameters (line center, fwhm and integrated flux) must be specified for an emission line to be included.

Question 4. Normalize the target's flux:

	(arcsec^-2 for extended sources) at
	(arcsec^-2 for extended sources) in filter:

	Filter selected above in Question 1 (for observations)
	Typically select Vega magnitude above
	Typically select AB magnitude above

Do not Renormalize Point Source Spectrum.Use only for User Input Spectrum or Calibration Spectra.

Question 5. Specify the expected background:

a)	Specify normalization for zodiacal background
	Standard zodiacal light normalizations:
	Compute zodiacal light on sky position (not a supported observation if target is within 50 deg of sun):
	R.A.: (hh:mm:ss or decimal degrees)
	Dec.: (dd:mm:ss or decimal degrees)
	either λ - λ_Sun: degrees
	- or - Date:
	Normalize high zodiacal light (V = 22.1 mag/arcsec^2) to Johnson V magnitude:
	Scale zodiacal light by factor (1.56 = average):
b)	Specify normalization for earth shine background
	Standard earth shine light normalizations:
	Normalize earth shine light to magnitude:
	Scale earth shine light by factor (0.5 = average):
c)	Air Glow