Figure 1.
GCAL spectral flat
data of new E2V
Deep Depletion CCDs
(white curve) versus
the old CCDs (red
curve) from GMOS
at Gemini North.
The data were taken
before the detector
gain values had been
precisely measured
and roughly scaled
to have the counts
match at 650 nm. The
data also could not
be used to derive any
absolute response,
due to inherent small
variability in the
GCAL quartz halogen
bulb brightness.
Notice, however,
the higher QE and
the near absence of
fringing with the new
detectors.
27
The gain in depth in z-band images is about
0.5 magnitude due to the increased quantum
efficiency (QE) and larger bandpass toward the
red. Compared to the old CCDs, the new ones
also have an increased sensitivity at the blue
end of the spectrum with 25 percent more QE
at 400 nanometers (nm), compared to 75 percent at 900 nm (see Figure 1). The improved
blue QE comes close to matching that currently obtained with GMOS at Gemini South.
We also have on-sky imaging photometric
zero-points for all of the broad-band filters,
showing that the realized on-sky gain in sensitivity is almost 0.4 magnitude in g-band. In
addition, we now have two new filters (Z and
Y) installed and available in GMOS at Gemini
North. Given the increased blue sensitivity,
we are currently exploring the option of replacing the u-band filter that delaminated
back in 2004.
The Hertzberg Institute of Astrophysics (HIA)
delivered the Hamamatsu CCD system to Gemini in December 2011, and we are now working in the lab to decrease the obtained readout
noise from the system. Our initial explorations
revealed signal quality and line filtering as
crucial keys for noise reduction. We have also
sought advice from various experts from with-
GeminiFocus
in the Gemini community and have reached a
consensus on how to pursue these issues.
Preliminary tests along these lines are very
encouraging, so we will continue implementing these improvements in the next
few months. We hope to begin installation
of these CCDs into GMOS-N starting January 2013. GMOS-S should be upgraded by
the second quarter of 2013. To find the latest
news and updates about the detectors, go to:
www.gemini.edu/sciops/instruments/gmos/
imaging/?q=node/10424
The Latest on FLAMINGOS-2
In 2011, the Development Team finished a
cycle of improvements to FLAMINGOS-2 in La
Serena and installed the instrument back on
the telescope on November 25th. After completing a successful technical commissioning
on the sky (including the first multi-object
spectra, see Figure 2 on next page), we intended to start System Verification with a Call
for Proposals in March 2012.
But FLAMINGOS-2 work came to a sudden
halt at the end of January 2012, when we discovered some vignetting in the images. After
a warm-up and inspection inside the instrument, we realized the main field lens (first lens
June2012