SpeX Science Modes
The primary science objectives of the instrument can be met with
the two cross-dispersed modes. The secondary science objectives
include two long-slit modes, and a low-resolution mode for
occultations and faint object spectroscopy.
Each of these modes
occupies one position in the grating turret. Spectral resolutions
are proportional to the slit-width and should be selected as
appropriate to seeing and diffraction. The spectral resolution
for the following modes is based on the narrowest slit available:
-
0.8-2.5 micron cross-dispersed,
R=2000 matched to a 0.3x15 arcsec slit (2x100 pixel).
Most of this range is covered simultaneously.
-
2.4-5.5 micron cross-dispersed,
R=2500 matched to a 0.3x15 arcsec slit (3.3x100 pixel). With
a small rotation of the grating turret the range
2.0-4.2 micron,
is also covered simultaneously.
-
0.8-2.5 micron single-order,
R=2000 matched to a 0.3x60 arcsec slit (2x400 pixel).
Single orders
are selected with order-sorting filters.
-
2.7-5.5 micron single-order,
R=2500 matched to a 0.3x60 arcsec slit (2x400 pixel).
Single orders
are selected with order-sorting filters.
-
0.8-2.5 micron single-prism mode,
R=250 matched to a 0.3x60 arcsec slit and to
one quadrant of the array. Since no gratings are required,
this mode is fast and efficient, making it particularly suitable
for low-resolution faint-object and time-resolved spectroscopy.
The slit-viewer may also be used as a 0.8-5.5 micron imager,
covering a 60x60 arcsec field-of-view at 0.12arcsec/pixel.
0.8-2.5 micron cross-dispersed,
R=2000 matched to a 0.3x15 arcsec slit (2x100 pixel).
Most of this range is covered simultaneously.
2.4-5.5 micron cross-dispersed,
R=2500 matched to a 0.3x15 arcsec slit (3.3x100 pixel). With
a small rotation of the grating turret the range
2.0-4.2 micron,
is also covered simultaneously.
0.8-2.5 micron single-order,
R=2000 matched to a 0.3x60 arcsec slit (2x400 pixel).
Single orders
are selected with order-sorting filters.
0.8-2.5 micron single-prism mode,
R=250 matched to a 0.3x60 arcsec slit and to
one quadrant of the array. Since no gratings are required,
this mode is fast and efficient, making it particularly suitable
for low-resolution faint-object and time-resolved spectroscopy.