|Space Telescope Science Institute|
|Handbooks HTML Update Nov 2014|
The F25QTZ filter with the NUV-MAMA provides high-throughput broad-band NUV imaging with better rejection of geocoronal emission than the F25MAMA or F25SRF2 modes, the same field of view, and the same high spatial resolution.Sky background on the day side of the orbit contains a significant contribution from [O II] air glow emission at 2471 Å. In high-background conditions, the sky background can dominate the detector background. In average day-side observing conditions about half the background will be from the sky and half from detector dark current. Observers can limit the background (with some cost to the total amount of observing time per orbit) by using the DARKTIME special requirement.Users should also consider whether the ACS HRC with the F220W or the F250W filter might be a better choice for their science goals.
Pivot λ (Å) Speak Bλ R80 (arcsec) Figure 14.35: F25QTZ NUV-MAMA Integrated System Throughput and RedleakTable 14.15: F25QTZ NUV-MAMA Sensitivity & Throughput
Figure 14.36: Point Source S/N vs. V+ABν for the F25QTZ NUV-MAMA mode. Top curves are for DARKTIME. Bottom curves are for average sky. Curves are labeled by required exposure time (sec.).Figure 14.37: Extended Source S/N vs. V+ABν for the F25QTZ NUV-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).
Figure 14.38: Point Source PSF for F25QTZ NUV-MAMA, 7."5 square (at pixel 606,649, log scaled). Note PSF ghost ~45 pixels left of peak pixel and a few 10-3 of the peak.Figure 14.39: Point Source Encircled Energy for F25QTZ NUV-MAMAFigure 14.40: Point Source Intensity vs. Radius for F25QTZ NUV-MAMA