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	Return to ETC Welcome SYNPHOT SNR and Exposure Time SNR Time Optimal SNR Spectroscopy Target Acquisition Basic Use Page Heirarchy Reference Extraction Regions Spectral Distribution User Spectra Other Spectra Extinction Normalization Background CCD Parameters ID Number Calculations SYNPHOT Calls Call Descriptions Call Parameters NICMOS Spectroscopic Extraction Regions Tables Spectral Elements NICMOS Filters NICMOS Dispersers ACS Filters and Dispersers COS Dispersers WFC3 Filters and Dispersers STIS Filters and Dispersers NICMOS Tables COS Tables STIS Tables and Topical Help

Other HST Spectrum

There are a large number of spectrum files available for use in Calibration Database System (CDBS). Some of these are discussed in the SYNPHOT User’s Guide in Appendix B. Any file in CDBS can be used if the user is able to determine a valid path name for the file.

For example, the Bruzual Synthetic Spectral Atlas (table B4) can be found in the CDBS directory "crgridbz77$", so to specify the F2V file from this atlas. Use filename "crgridbz77$bz_19.fits" in the ETC user input form as shown below.

HST Standard Spectra (CALSPEC and CALOBS)

CALSPEC contains the composite stellar spectra that are the fundamental flux standards for HST calibrations. All files are in machine independent binary FITS table format. Information about the pedigree of a given spectrum is in the header of the FITS table file. Further details about these files as well as access to these files can be found at http://www.stsci.edu/hst/observatory/cdbs/calspec.html

CALOBS contains several versions of the ultraviolet (UV) and optical spectra of the fundamental flux standards used for HST calibrations. Some of these files contain the original data obtained from different sources (UV: VOYAGER2 or IUE; optical: Tapia or Stone; or STIS), while others contain corrected or updated versions. Updates to the flux distributions are indicated by file names with the same root name but incremental version number. The earlier versions are retained for comparison purposes. All files are in machine independent binary FITS table format. Information about the pedigree of a given spectrum is in the header of the FITS file. Further details as well as these files can be found at http://www.stsci.edu/hst/observatory/cdbs/calobs.html

How to use "Other HST Spectrum" in the ETC

To use one of the CDBS supplied spectrum file, select the "Other HST Spectrum" option in section 3 of the ETC input form and type the file path in the text box as shown below: