SAO Exposure Time Calculator Help Page

THIS SOFTWARE IS STILL IN BETA, PLEASE REPORT BUGS TO kurtz@cfa.harvard.edu

The plots are the SN per resolution element and the counts per pixel or ergs/sec/A for the selected instrument, spectrum and observing conditions

Parameters

• Instrument & Mode --- Choose from the dropdown
• Spectrum Type --- Choose from the cascading dropdowns
• Anstroms per pixes --- Set by program
• Arcsec per pixel --- Set by program
• Redshift --- Reset from template observed to desired
• AB Mag in observed band --- Choose desired, band is set below
• Source Effective Radius --- Choose desired Half light radius in arcsec
• Exposure Time --- Choose desired
• Seeing --- Choose desired
• Moonage --- Choose desired, dark is 0, full is 14.765
• Bandfilter --- Choose from dropdown, corresponds with AB mag of source
• Plot Spectrum --- Plots SN and spectrum in counts per pixel
• Aperture Type --- Choose from dropdown
• Ap Width --- Choose desired
• Ap Height --- Only appears if rectangular aperture is chosen
• Plot Flux --- Plots SN and spectrum in ergs/s/A
• Airmass --- Choose desired
• Retrieve Data Table --- Prints the SN, Flux and Counts in a new tab

To see the region covered by the higher dispersion gratings, use the cursor to expand the plot to blow up the area corresponding to the grating tilt.

Several of the template spectra (the stars, for example) are lower resolution than the spectrographs produce. The S/N will be correct, but the fine details will be off. If you have a high S/N spectrum which would make a good template please consider contributing it.

The photometric bandpass (g,r,i) must overlap with the redshifted template. Some templates were observed in the IR, and must be shifted to lower z to appear in the optical, for example.