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Hubble Space Telescope
FGS Filters

The filter wheel preceding the dielectric beam splitter in each FGS contains five 42mm diameter slots. Four of these slots house filters-F550W, F583W, F605W and F5ND-while the fifth slot houses the PUPIL stop. This stop helps restore the S-Curve morphology throughout the FOV of each FGS by blocking out the outer 1/3 perimeter of the spherically aberrated primary mirror. The filter selection for each FGS, their central wavelengths, and widths are listed in the table below. The transmission curves (filters and PUPIL) and PMT efficiencies are given in the figures below.

Figure 1. FGS1r Filter Transmission Curves:

Table 1. Available Filters
Filter Central Wavelength
Spectral Range
F583W 5830 4600-7000 2340 1,1R,2,3
F605W 6050 4800-7000 1900 1,1R,2
PUPIL 5830 4600-7000 2340 1,1R,2,3
F550W 5500 5100-5875 750 1,1R,2,3
F650W 6500 6200-6900 750 3
F5ND 5830 4600-7000 2340 1,1R,2,3

Figure 2. PMT Efficiency: