Figure 2. IIIaF versus Tech-Pan H-alpha sensitivity curves

Figure 2 gives the IIIaF (left) and Tech-Pan (right) emulsion sensitivities as a function of wavelength through a 100Angstrom H-alpha filter as obtained with a calibration spectrograph. Identical aperture settings and exposure times (180mins) were used for both emulsion samples. The figures basically represent flux trasmitted through the narrow-band filter and recorded by each emulsion. These results convinced us there was no speed, sensitivity or reciprocity penalty in adopting Tech-Pan for use with a narrow-band H-alpha filter c.f. IIIaF. the tick mark is at a wavelength of 5460 Angstroms whilst the right hand edge of both sensitivity curves is close to 7000 Angstroms.