|STIS Instrument Handbook for Cycle 25|
The STIS aperture wheel has 65 positions, several of which correspond to multiple slits or masks. Only a small fraction of the full complement of spectroscopic apertures are currently supported. Table A.1 and Table A.2 provide a complete list of STIS apertures for spectroscopy, together with comments regarding their characteristics or purposes. For most apertures, the aperture name gives the length in the spatial direction by the width in the dispersion direction in arcseconds. Schematics of three complex apertures are given in Figure A.1, Figure A.2, and Figure A.3.
Table A.1: STIS Spectroscopic Apertures. Supported apertures are in boldface. 0.1X0.03 0.1X0.06 0.1X0.09 0.1X0.2 The latter two are supported with E230H only. The 0.1x0.03 is supported with all echelle gratings. 0.2X0.06 0.2X0.09 0.2X0.2 0.2X0.5 0.2X0.06 and 0.2X0.2 are supported with E230M and E140M, while 0.2X0.09 and 0.2X0.2 are supported with E230H and E140H. 2X2 6X0.06 6X0.2 6X0.5 6X6 The 6X0.2 long slit is supported with the echelles. 52X0.05 52X0.1 52X0.2 52x0.5 52X2 Long slits for use with the echelles. 52X0.05 is supported, and the others are available-but-unsupported with the echelle gratings. F25MGII F25CN270 F25CIII F25CN182 Narrow-band filters. F25MGII is supported for E230H and E230M. Others are available with the NUV-MAMA only. Available-but-unsupported with the FUV-MAMA only.
Table A.2: STIS Spectroscopic Apertures. Supported apertures are in boldface. These CTE aperture positions are centered near row 900 on the STIS CCD detector; however, the positions are offset from the physical aperture centers to give better alignment with fringe flats done using the 52X0.1 aperture. The E2 positions are supported for the G750L and G750M gratings only. These aperture positions put a target near the bottom edge of the FUV-MAMA and are intended for observation of very faint targets where it is necessary to minimize the contribution of the FUV-MAMA dark current. They are all supported with the G140L and G140M gratings. 52X0.05D1 and 52X0.1D1 are also supported for CCD peakups. 52X0.05F1 52X0.05F2 52X0.1F1 52X0.1F2 52X0.2F1 52X0.2F2 52X0.5F1 52X0.5F2 52X2F1 52X2F2 Fiducial bars on the long slits which can be used for coronagraphic spectroscopy. The 52X0.2F1 is supported for all first-order gratings and is available-but-unsupported for the PRISM. The other fiducial bars are available-but-unsupported with all gratings and the PRISM. The F1 and F2 bars are 0.5 arcseconds and 0.86 arcseconds long, respectively (see Figure 13.1). 0.1X0.03 0.1X0.06 0.1X0.09 0.1X0.2 0.2X0.06 0.2X0.09 0.2X0.2 0.2X0.5 0.3X0.06 0.3X0.09 0.3X0.2 1X0.06 1X0.2 6X0.06 6X0.2 6X0.5 0.2X0.05ND 0.3X0.05ND As of Cycle 12, the 0.2X0.2 aperture is supported for use with all first-order gratings; it is available-but-unsupported with the PRISM. While not supported for first-order observations, the other echelle apertures can be used in first order as available-but-unsupported apertures. This includes the echelle neutral-density slits 0.2X0.05ND and 0.3X0.05ND with dex ND factors of 2.0 and 3.0, respectively. F25QTZ and F25SRF2 are supported for all MAMA gratings and PRISM, but are unavailable with the CCD. These aperture positions put a target near the bottom edge of the FUV-MAMA and are intended for observation of very faint targets where it is necessary to minimize the contribution of the FUV-MAMA dark current. They are all supported with the G140L and G140M gratings. F25MGII F25CN270 F25CIII F25CN182 F25MGII is supported and these other filters are available -but-unsupported with the NUV-MAMA gratings and PRISM only. The F25LYA filter is available-but-unsupported with the G140L, G140M, E140H, and E140M gratings only. Long slits of given dimensions in arcseconds, inclined at ±45° to facilitate observations of moving targets at off-nominal rolls. See Figure A.1.Figure A.2: Schematic Showing the SIS 45° Slits Design. A second pair has the same morphology but widths of 0.6 arcsecond (central) and 2.0 arcsecond (peripheral).