This is the same physical aperture as the F25SRF2
aperture and has become available for use with the FUV-MAMA
detector to minimize the contribution from the dark current when observing very faint targets. This aperture moves the target 2 arcseconds above the bottom edge of the FUV-MAMA
. It is yet to be determined if the throughput for a target at this position is significantly different from that obtained at the standard position.
Usage of this slit is only allowed with the G140L
gratings. For more information on throughputs, encircled energy, etc., please refer to the information for “F25SRF2—FUV-MAMA, Longpass”