The IMACS team is pleased to announce the debut of IMACS as a
multislit spectrograph. This 3000 sec. exposure of RCS2347.3-3634 at
z~0.5 was taken last night with the f/2 camera and the 200l/mm grism.
The multislit mask has 240 (0.8" wide) slits on galaxies, and 7
stars were used to align the field with the slit mask.
The first image on the sky was taken with IMACS on Baade (Magellan I)
on Tuesday morning, August 19th, at about 2:00 a.m. The target was
the nearby dusty Sc galaxy
NGC 253
which stretches for nearly 1/2 deg over the sky. The first exposure
was a guided 300 s V-band 1x1 image with the f/2 camera and the full
8k x 8k Mosaic CCD camera.
About 18 people crowded the control room to share the pleasure of
seeing this beautiful image scroll down the screen. The stars on this
image ranged in size from 0.9" in the center to about 1.5" on the
outside.
After champagne toasts, huge smiles, and lots of enthusiastic
back-slapping, Skip Schaller checked the center-field Shack-Hartmann
test and found that the focus had drifted substantially since the last
check. The guide cameras showed seeing of about 0.5", in good
agreement with what Ian Thompson and Greg Burley were getting on the
Clay (Magellan II). A second 300 s exposure was taken and this one
produced 0.55" images in the center, better than had been expected
without the ADC corrector and the IMACS f/2 camera. More joy. See
a detail from the second image below.
Many more pictures were taken of NGC253 with 4 filters and at
different positions to make a pretty picture -- which we will post
here as soon as we figure out how to handle all the data!
IMACS assembly is now basically complete except for the f/4 camera
kit, which we hope to install tomorrow. We have many more tests to do
in our remaining two nights -- more news as it happens.
The IMACS team
