• Two detectors are available for OASIS.  The first, Loral 3, has been used since the arrival of the instrument here at CFHT.  In June 2000, a new chip, EEV1, has replaced EEV2 in its dewar, the detector  previously used for Gecko.  This new device has a much better QE than Loral 3, a smaller readout-noise and faster readout-time.  Its characteristics can be found here . However, since it's a thin chip, fringing is very important over 7000A. The peak-to-valley amplitude reached about 35% at 8500A. No useful science can be done in the red range (> 7000 Ang.) of OASIS with EEV1.   So, if your program requires configurations in the red domain (e.g. LR2, MR3, MR6, MR7, HR5), it is preferable to use Loral 3 instead of EEV1.    However, only ONE change of CCD will be allowed during an entire observing run with OASIS. In other words, only one CCD will be mounted for a given program so you can use one CCD or the other but not both.  The exposure time simulator has now integrated the characteristics of EEV1 and can be used for planning your observations with this device.  The pixels of EEV1 are smaller than Loral3  so, make sure to read the Instrument Overview page to understand what it means for OASIS. For more information, please contact me !

• An updated postscript version of the OASIS cookbook is now available! It includes some guidelines for observing with OASIS and more! For Loral3, use this version. For EEV1, use rather this version. It might be useful for you if you're planning your observations with OASIS so please, have a look! Since OASIS is still a "new" instrument, I am trying to keep it updated with the new procedures and information. Do not be afraid by the ``complicated'' look of the observing procedures. Observing with OASIS is easy and it becomes quite automatic after a few hours...

 
• Good news! Analysis of set of data taken during the 2000 runs has shown that the Atmospheric Dispersion Corrector (ADC) is working properly. This device is essential for the very high spatial resolution of OASIS. Unfortunately, this device was never fully used prior to the OASIS runs so we have discovered problems in the way the device is controlled. Some hardware and software modifications had to be implemented. At this moment, the correction is still not totally optimized but residues are small at about 0.01"....

 
• All the AOB beamsplitters have been used! Their characteristics have been gathered at CFHT and their coatings were found to be excellent and within specifications. The transmission curves are now available on this page. Changing beamsplitters is possible during an observing night but each operation results in about 15 minutes lost on the sky. Observations MUST be planned to minimize lost of observing time. However, we found that the splitters were not perfectly aligned with each other and worse, that their position is not perfectly kept if they are dismounted and remounted again. This means that for each beamsplitter change, the wavefront sensor hotspot has to be redefined. This takes some time so this is another reason to avoid changing beamsplitter too frequently during a night.

 
• The f/8 mode of OASIS is fully implemented. Its availability makes OASIS a very versatile instrument, well adapted to different seeing conditions. The mode is easy to use except for a few complications in the telescope focussing procedure. The interface has been modified so that the observers are automatically prompted and asked to change the telescope focus, if necessary. It is then very important that the observers arrive with a backup program that can make use of this mode if the seeing becomes larger than 1.2" (i.e. limit for the AO correction).

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