ACS Imaging ETC

This form will calculate the count rates and S/N ratio for a simulated spectrum of ONE source in an ACS 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 ensure that you have read the current release notes and recent news before submitting any ETC calculations.

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

Detector Filter Wheel 1 Filter Wheel 2
 
CCD parameters:
Gain Setting # Frames Post Flash [e]

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:


3. Choose one of the following spectral distributions for the source:

Please note: for User supplied and uploaded spectrum, please use only FITS or text (DAT) format files.
Upload Spectrum File:
Other HST Spectrum:
CDBS Synphot spectrum file
Castelli and Kurucz Models: [Sp Teff log(g) log(z)=0]
Pickles Models: (Sp Teff)
Kurucz Models:
Bruzual Synthetic Stellar Spectra:
HST Standard Star spectra:
Non-Stellar Objects:

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 extinction, renormalization, 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.

4. Normalize the target's flux:

= (Vega magnitudes) (arcsec-2 for extended sources)
= (AB magnitudes) (arcsec-2 for extended sources)
Normalize target using bandpass of filter selected above to AB Mag
ergs cm-2 s-1 Å-1 (arcsec-2 for extended sources) at Å.

5. Specify the expected background levels :

a) Specify normalization for zodiacal background
R.A.: (hh:mm:ss or decimal)
Dec.: (dd:mm:ss or decimal)
either degrees
- or -
b) Specify normalization for earth shine background
c) Air Glow