Handbook Reference
Guide
Why Use the FOC?
Primarily the FOC serves as an imaging camera, but the possibility to use objective prisms and the F/48 long slit facility provide also some spectrograhic capabilities.The following are just some of the unique properties of the FOC.
- Spatial Resolution: The FOC offers imaging capabilities with a pixel size of 0.014" and a FWHM of less than 2 pixels (less than 0.6 Planetary Camera pixel). The dependence of the FWHM on wavelength is described more fully in .
- UV Sensitivity: The FOC provides peak sensitivity at 3400Å and better sensitivity than the WFPC2 for all observations with l < 4000Å, down to 1150Å. "Absolute Quantum Efficiency" on page 70 discusses the overall throughput of the FOC, while the large selection of UV filters are described in "Filter Wheels" on page 28.
- Polarizers: The FOC provides three polarizer filters with pass directions of 0xfb , 60xfb and 120xfb . These filters provide a straight-through, low reflection-angle system which introduces less than 5% intrinsic polarization. The specifics of these filters and their calibrations can be found in "Polarizers" on page 41.
- Objective Prisms: There are two objective prism filters for use with the FOC, operating in the near-UV and far-UV regions. Objective prism images allow spectra to be obtained for different regions of a spatially resolved object at the same time with high throughput, and low- to medium- resolution from 1700Å - 6000Å for the near-UV prism and 1150Å-6000Å for the far-UV prism. "Objective Prisms" on page 39 discusses the resolution and throughput of the prisms in more detail.
- Deep Photometry of Point Sources: The low detector background and its insensitivity to cosmic rays allows for long exposures providing very deep photometry of point sources in the field of view, reaching a S/N of 10 for a V=26 B5V star in a 45 minute exposure. The limiting magnitudes are discussed in more detail in .
- F/48 Long Slit Spectroscopy: The F/48 relay contains a long-slit spectroscopy facility for obtaining spectra with a resolving power of ~1150 in 4 orders spanning from 3600-5400Å, 1800-2700Å, 1200-1800Å, and 1150-1350Å. Problems with the F/48 relay have hampered its use in the last three cycles, but long slit spectroscopy will be offered as the sole use of the F/48 relay in Cycle 6. "Long Slit Spectrographic Facility" on page 44 discusses this facility in more detail, while "Current F/48 Performance" on page 91 describe the current performance of the F/48 detector itself.
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