|STIS Instrument Handbook for Cycle 26|
The F25SRF2 filter with the FUV-MAMA provides high-throughput broad-band FUV imaging with better rejection of geocoronal emission than the F25MAMA but worse than F25QTZ modes. It provides the same field of view and spatial resolution as these modes.This filter has slightly higher throughput than F25QTZ, but lets in geocoronal [O I] 1302 + 1306 Å. For sky-limited imaging F25QTZ is usually a better choice.Sky background on the day side of the orbit contains a significant contributions from [O I]/O I air glow emission at 1356 Å and at 1302 + 1306 Å. In high-background conditions, the sky background can dominate the detector background. In average day-side observing conditions the sky background through this filter will be about a factor of 100 higher than for F25QTZ. Observers can limit the background (with some cost to the total amount of observing time per orbit) by using the DARKTIME special requirement.Users may also want to consider whether the ACS SBC detector might be better for their observing program.
Pivot λ (Å) Speak Bλ R80 (arcsec) Table 14.34: F25SRF2 FUV-MAMA Sensitivity & Throughput
Figure 14.84: Point Source S/N vs. V+ABν for the F25SRF2 FUV-MAMA mode. Curves are labeled by required exposure time (seconds).Figure 14.85: Extended Source S/N vs. V+ABν for the F25SRF2 FUV-MAMA mode. Top curves are for an area of 0.2 arcsec2; bottom curves are for 1 arcsec2. Average sky assumed. Curves are labeled by required exposure time (seconds).Table 14.35: Radial Profile for F25SRF2*
Figure 14.86: Point Source Encircled Energy for F25SRF2 FUV-MAMAFigure 14.87: Point Source Intensity vs. Radius for F25SRF2 FUV-MAMA