CFH12k on the Sky!

• Rohendra Atapattu
• Bob Calder
• Jean-Charles Cuillandre
• Sidik Isani
• Wiley Knight
• Grant Matsushige
• Nick Meheula
• Les Mizuba
• Wayne Pexa
• Dan Sabin
• Derrick Salmon
• Bobby Song
• Barry Starr
• Ralph Taroma
• Yasu "Roger" Uchima
• Dan Wilcox
• Roger Wood

Jan 11/12

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!

• 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
• residual images
• fringing (critical in I band)
• flattening efficiency

Good Morning,

Yes, I do feel lucky: 0.55 arcsecond seeing data in the I band on 10 minutes exposures!

Actually it is just that we have a great instrument on a  great telescope.

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.