CFH12k on the Sky!
CFH12k is sucessfully taking data; make that large
amounts of data. The world's largest CCD mosaic camera is on the telescope
and working very well.This would not have even come close to happening
without the hard work and dedication of many CFHT staff members and Gerry
Luppino of UH IfA. The CFHT staff involved in
this heroic effort include (in alphabetical order):
Reports from Jean-Charles Cuillandre on the last two nights (Jan 11/12
and 12/13) follow. The first night was straight engineering while the second
was split with observers (Olivier Le Fevre and Olivier Boulade). Here are
three sample images: small, low-res and high-res of M81.
Yasu "Roger" Uchima
A great success! I've never taken so much data in one single night;
not only is there a lot but it is all very good and shows that the
CFH12K is a highly efficient instrument.
You read Barry's email about the few glitches at the beginning of the
night, but that night ended up with about 200 exposures taken on the sky
(it means 200 activations of the shutter at various hour angles, some as
extreme as 4:40!). Overall it is about 35 Gigabyte of data collected
in 10 hours!
First of all, this night could not have been without the ultra effort
put by Barry on the filter wheel. It works great and we control it from
the session. A working filter wheel boosted my work by a factor of 4 at
least, hence I I had time to look around in the sky at some wonderful objects
I will share with you soon.
Sidik's software is rock solid, not one exposure was lost, none of
the systems had to be restarted. Now we are setting the high level interfaces
to the telescope and the user.
Many thanks to Marie-Claire Hainaut (OA) for her high efficiency trough
this frantic long night as we finished late with twilight flats and
dome flats in all 4 filters!
Christian Veillet was supporting us from down in Waimea, analyzing some
of the data we were taking to prepare us for the next steps. This
helped a lot in improving our efficiency on the sky. Here are some
topics addressed tonight:
With this very short readout time (1minute for the full mosaic), taking
twilight flats and dome flats is no more a pain. It is very fast. No risk
anymore to miss breakfast time at HP!
There are still some engineering work to conduct over the next two nights
(but the main bulk of work has been
All of the telescope offset and bonnette tools work great and help a lot
to reduce overheads between exposures. They have been extensively used
last night and are very robust (focus script, offset, Z set). A note: moving
the bonnette Z does not generate noise in CCD readouts. 15 seconds can
be saved there if we apply that.
With the working filter wheel, I was able to jump from one filter to another
very quickly. There is no problem focusing through the B,V,R and I filters.
I took "Z plates" in 12K8K format for each of these filters to investigate
further image quality issues. We noticed a weird halo on B frames: we can
see the image of the cage+spider+top end around bright stars. This
might be an issue for precise photometry work.
The bonnette should not be rotated anymore for the coming run: Marie-Claire
has been able to align it so we have less than a pixel of the width of
a CCD (2K pixels).
We don't have enough disk space! It will probably be ok with
normal observing runs. I pushed it to the limit. So far in 2 nights, I
collected something like 50 Gb of data!
I worked a lot on the photometric calibration of the camera since the night
was photometric. I used the field RU149 and put it on each CCD for all
filters (count how many exposures that is...). Then I used
the large standard field SA98 to check ballistic effect of the shutter
on the photometry. I also used that field (and again on all
filters) to take several exposure shifted 50 pixels from each
other to investigate the effect of the CCDs brick wall pattern on
the photometry. Shifted exposure along the diagonal of CCDs
was taken to investigate effect of CTE loss on photometry.
For several hours we got the shutter firing every 10 seconds and tons of
data flowing to the disk. Thanks to scripting capabilities and reliable
hardware, the whole process took less time than predicted.
It means there was some time available for doing some science. I
observed M33 in B,V and R to continue some works on stellar populations.
Christian got one of his fields observed at two different time (search
for transient objects). I also took other pictures that will be a
great support to advertise this new facility to the world:
a pretty galaxy filling the whole field (M81), a globular cluster (M3),
a cluster of galaxies (Coma). From another night we have some nebulae
(M42 and the Horse nebula).
shutter ballistic (further investigations
fringing (critical in I band)
Yes, I do feel lucky: 0.55 arcsecond seeing data in the I band on 10
Actually it is just that we have a great instrument on a great
The night started with the French observers who were very happy (or
surprised?) that every went so well: not one problem and they already collected
a large set of high quality data. Olivier Lefevre and Olivier Boulade both
had a big smile on their faces! They got data down to 0.6" in the I band.
Thanks to automatic focus scripts and sequence observing scripts, the
efficiency of the camera is very high: only 1mn30sec of overhead between
exposures. We are really spending most of the time with the shutter open
(typical exposure time is 10mn).
Then the second half-night was for CFH12K team. Residual images tests
were taken on a star field, along with some photometric calibrations.
The dome temperature is higher by 5 degrees compared to yesterday
and the Z to focus all 4 filters has gone down by 0.5mm. The increase
of the CCD temperature is related to this external increase. We will have
to set a higher working point for the temperature regulation for the next
run (let's keep it like this for this run).
Three fields were taken for Christian during the night, and I got to
observe a field in B and I. Hell, I got 0.8" in the B band (8x10mn
exposures) and then 0.55" in the I band! This is great stuff. I hope
to successfully complete these observations tomorrow as a high signal to
noise ratio is required. We have great sensitivity (a 4meter
telescope and thinned CCDs), and we have an outstanding image quality
that allows detecting small and faint objects.
Oh, I forgot to mention: the camera behaved perfectly tonight.