|Space Telescope Science Institute|
|Cycle 23 STIS Instrument Handbook|
The PRISM has two central wavelength settings optimized to cover the optical through the far-ultraviolet (FUV) tail down to 1150 Å. It is used with the NUV-MAMA detector.The full dispersion spreads over ~450 pixels with dispersion as shown in Figure 13.64, PRISM dispersion-wavelength relationship.; thus if you have sources covering the field of view in the dispersion direction, the red tail will be lost for some targets with this setting. For a plot of wavelength vs. pixel no., see Figure 4.12, Wavelength vs. Pixel Number along the Central Spectral Trace for the PRISM at Wavelength Settings 1200 and 2125 Å.We note that the dispersion of the PRISM at wavelengths longer than ~2600 Å is very poorly known at this time.
Figure 13.62: Wavelength Range for the Prism SettingTable 13.17: PRISM Throughputs & Sensitivities for a Point Source
Point source sensitivity assumes full transmission (zero slit losses). Diffuse source sensitivity assumes a 0.1” wide slit. To convert point source sensitivities to diffuse source sensitivities multiply the point source values by the grating spatial (cross dispersion) plate scale in units of arcseconds per pixel and by the width of the desired slit in units of arcseconds.