|STIS Instrument Handbook for Cycle 25|
The F25LYA filter with the FUV-MAMA provides narrowband imaging of the HI 1216 Å Lyman-α line.Lyman-α imaging. Differencing two images taken with 25MAMA and F25SRF2 is another option.Sensitivity is limited by geocoronal Lyman-α. 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 with the F122M filter might be a better choice for their observing program.
Pivot λ (Å) Speak Bλ R80 (arcsec) Figure 14.88: F25LYA FUV-MAMA Integrated System Throughput and RedleakTable 14.36: F25LYA FUV-MAMA Sensitivity & Throughput
Figure 14.89: Point Source S/N vs. flux for the F25LYA FUV-MAMA mode. Curves are labeled by required exposure time (seconds).Figure 14.90: Extended Source S/N vs. flux for the F25LYA 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 14.37: Radial Profile for F25LYA*
Figure 14.91: Point Source PSF for F25LYA FUV-MAMA, 7."5 square (at pixel 739, 368, log scaled, B-V=-0.04)Figure 14.92: Point Source Encircled Energy for F25LYA FUV-MAMAFigure 14.93: Point Source Intensity vs. Radius for F25LYA FUV-MAMA