Currently, the supported coronagraphic capabilities of STIS include
a selection of positions within the 50CORON aperture along one of two
wedges, and a single position along a bar at the top of the detector.
The smallest of these supported positions is at WEDGEA0.6,
corresponding to an inner working angle of ~0.3". An outsourced Cycle
20 STIS calibration program, 12923 (PI: Gaspar), recently investigated
new aperture locations located near the corners of the coronagraphic
bar (BAR10) as well as at the "bent finger" wedge (BAR5) located on the edge of
the aperture. These new positions allow high contrast imaging at a
minimum inner working angle of 0.15", with demonstrated performance
to ~0.2"--roughly 3 lambda/D, and close to a factor of two better than WEDGEA0.6.
A summary of the initial results of this program as well as detailed suggestions
on how to implement observations using these new aperture positions are
available at:
http://www.stsci.edu/hst/stis/strategies/pushing/coronagraphic_bars.
These new aperture positions are
currently unsupported in APT. While the use of these new coronagraphic
positions may become fully supported in a future cycle, for Cycle 22 they
will remain "available-but-unsupported", and users must accept some
additional risk for observations using them. See
section 2.3 of the STIS Instrument
Handbook, for a full discussion of these policies.
