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Interference filters

The interference filters available for use with TAURUS--2 are listed in Table 12

When these filters are mounted in the focal plane filter wheel, it is possible to shift their central wavelength to the blue ( not to the red) by tilting the filter (Lissberger & Wilcock Journal of the Optical Society of America, vol 49, p126, 1959). At a tilt angle theta degrees, the effective wavelength Leff depends on the nominal wavelength Lnom as:

This equation assumes a refractive index for the filter of 2.1. The maximum tilt possible is 10 degrees. This gives a fractional shift in the effective wavelength of about one third of one per cent, corresponding for example to a shift of 17 Å at a wavelength of 5000 Å. Note however that tilting the filter also results in a broadening of the bandpass and a reduction in the peak transmission.

Thu Apr 7 00:29:52 BST 1994