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Palomar Adaptive Optics System Results
On 12/20/01 Titan occulted both stars of a binary system (separation ~1.5 arcsec
onds). The image above shows Titan just starting to occult the firststar. The sp
atially resolved observation of the occultation provides a new, powerful techniq
ue for investigating Titan's atmosphere from Earth that is only possible using a
daptive optics. Click on the image to view a movie of the event or "here" for more information.<
br>
The above figure shows a possible detection of a binary c
ompanion. The delta magnitude between the primary and brighter companion is 13
in K and the separation is about 5 arcseconds. Observation by Matthew Britton a
t Caltech
Image of AO corrected star HD 155394, 1 April 2001 (right), and a corresponding
uncompensated image (left), displayed on a logarithmic scale. The Strehl ratio
with correction is > 65%, and the image wavelength is ~2.166um. The image is 3
arcsec x 3 Arcsec, the pixel sampling is 0.025 arcsec/pixel, and the total integ
ration time is ~100 seconds for each image.
M8, the Lagoon Nebula 01 Aug 1999
Thirty-second exposure open-loop (left) and closed-loop (right) J,H,K-band
composite images of the Lagoon Nebula, MA, taken in poor conditions with the Pal
omar
Adaptive Optics System and the Palomar High Angular Resolution Observer. The
top center two sub-images demostrate the increase in resolving power provided
by AO, while the lower three demonstrate the anisoplanacity of the AO corrected
field. The K-band image FWHM falls from approximately 0.2 arcsec at the field
center to greater the 0.6 arcsec at the edge of the 40X40 arcsec field of view.
August 1999
These near-infrared images of the planet Uranus were taken with the JPL Palomar
Adaptive Optics (AO) System and the Cornell PHARO camera on August 1, 1999.
The AO system was locked on the disk of the planet to produce about
0.25 arcsec angular resolution. At 1.2 and 1.6 microns, atmospheric
features around the north pole and near the equator are visible. At 2.2
microns, methane absorption renders the disk of the planet almost invisible,
although faint limb-brightening can be detected. The Uranian
ring system and two moons: Miranda (magnitude ~15) and Puck (~19), are
most easily visible in the 2.2 micron image where interference from the
planet is minimal.
May/June 1999
In May/June of 1999 we had three nights of enginnering time (May 30,31
and June 1). Preliications are that we achivied diffraction limited
images in J-band (0.052" lambda/D) at an estimated 5% Strehl and 0.091"
(lambda/D) K-band diffraction limit at estimated > 30% Strehl, in the presence
of 0.6 - 1.2 arcsec seeing (K). Science modes included coronagraphy (0.41"
spot) and spectroscopy with 0.2" slit. The loop was closed on guide stars
as faint as mV = 11. Below are preliminary results, stay tuned for more!
December 1998
In December of 1998 we achieved our first high order image correction.
We had 5 half nights of time (5 hours per night). On three of the nights
seeing was greater then 2.7" at 0.5 microns. On one night (December 18th)
it was 1.6" at 0.5 microns and we were closed 1 night due to bad weather.
On the nights of July 28-Aug 01, the Palomar AO system and the PHARO science
camera were tested at Palomar Observatory in excellent seeing conditions. Low
wind speeds and good weather helped the AO system achieve diffraction-limited
resolution (as fine as 0.050 arcsec) through the Earth's atmosphere. K-band (2.
2 micron wavelength) Strehl ratios, guiding on a point source, were over 50%,
while J-band (1.2 micron) Strehls were 25%. Image improvement when guiding on e
xtended
sources was measured to be somewhat less.
This collection of images shows the progression of scientific
investigation of the very low mass star, Gliese 105C, the faint star
located 3 arcsec to the upper right of the bright star Gliese 105A, in
these images. The scale and orientation of all of the images are
approximately the same, except that the bottom left image is rotated by 16
degrees clockwise.
The upper left image is a ground-based image, taken at the 60" telescope
at Palomar. This image confirmed the fact that the fainter star, Gliese
105C was indeed a companion of Gliese 105A. In the center of this image
is a dark, circular, coronagraphic stop, used to suppress the scattered
light from the primary star.
The lower-left image is a later ground-based image, taken at the 200" at
Palomar, containing a different coronagraphic mask.
The lower-right image is from WFPC2 aboard Hubble Space Telescope, in this
case at visible wavelengths. No coronagraphic mask was present. Compared to
the earlier ground-based images, HST provided a significant increase in
contrast between the primary star and the companion.
The upper right images was taken by the Palomar AO System/PHARO camera
combination at the 200" telescope. Again, no coronagraphic mask was used.
The primary star, however, in this case exhibits a fourfold 'square'
pattern, which is an artifact of the AO instrument, and could be removed
in postprocessing. The contrast between primary and companion is
excellent. This improvement allowed the AO team to collect previously
unobtainable infrared spectra of Gl 105C which are currently being
analyzed.
In all the pictures, the color scale is meant to show approximately the
extent of the primary star's scattered light contribution to the image.
In the vicinity of Gliese 105C, it is quite clear that the AO system has
controlled this light very substantially, to the point where essentiall
none of Gliese 105A's light is present at Gliese 105C. This is not the
case with any of the three other imaging techniques. (n. b. The Palomar
AO image and the Palomar 200" image were taken through the 2.2 micron
infrared K band. The other two images were taken at the 0.8 micron
optical i or I band.)
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