Table 1.2.1



FOS Observed Counts Sec-1 Diode-1 (Nl ) for Point Sources at Wavelength l (Å)

Flux Distribution

1. Continuum

2. Monochromatic



3. Normalized 

Continuum





4. Planck Function







5. Continuum



6. Normalized 

Continuum



7. Power Law n-a

Inputs

Fl(ergs cm-2 s-1 Å-1)

Il(ergs cm-2 s-1)











Fl(ergs cm-2 s-1 hz-1)







Equation for Nl (counts- sec-1 diode-1)

2.28 x 1012 FlDlElTl

2.28 x 1012 IlElTl











El = (Net HST Reflectivity) x (FOS Efficiency at Wavelength l (Å)) x (COSTAR efficiency). See Figure 1.2.1.

Tl = Throughput of aperture at Wavelength l (Å) as simulated based on Telescope Image Modelling software (Burrows and 
Hasan 1991). See Figure 1.2.2.

Dl = Number of Angstroms per diode at Wavelength l (Å). See Table 1.1.1. 



Note that the relevant count rate to derive SNR per resolution element is Nl (counts- sec-1 diode-1). A resolution 

element is one diode, regardless of sub-stepping.