GMOS Hot News

October 25, 2007
Gemini is now providing GMOS users the option to design MOS masks without requiring GMOS pre-imaging of the field. This capability is offered at your own risk, and is not recommended for use by all programs. For MOS programs using slits narrower than 1.0" or for programs requiring very long observations of faint targets, Gemini recommends one continues to obtain pre-imaging of the field prior to designing the MOS mask. Please see the GMOS Multi-Object Spectroscopy webpages for an overview. The details of MOS design using object catalogs are linked from the GMOS MOS Mask design instructions. Please be sure to read the recommendations to ensure good mask design when using object catalogs. We thank the UK NGO office for their assistance in enabling this enhanced MOS capability.

October 23, 2007
Attempts to remove the GMOS-N flatfield features have not been successful. We are waiting for a suitable opportunity in which to more aggressively attack the situation, but that might require significant amounts of GMOS-N downtime which is not easily accommodated. Until then, users of GMOS-N imaging data should continue to employ twilight flats taken as close in time to their science imaging data as possible. The flatfield features do appear to divide out nicely and do not impact the sensitivity of GMOS very much or over a large area.

September 24, 2007
The GMOS Mask Design Instruction web page was updated on UT September 10. New instructions for PIs about the standard naming convention for mask submissions have been added.  A link to the mask design check document used by the National Gemini Offices for mask design checking has been also included. The PIs are welcome to read these instructions to check and improve the mask design.

March 20, 2007
The GMOS-N flatfield features have recently changed in appearance. Observers reducing imaging data obtained since UT February 27, 2007 should take care to employ twilight flats also taken since this date. Attempts to clean the optical surfaces within the GMOS-N camera have not resulted in changes in the feature's appearance, yet the shape changed noticeably after a power outage caused the dewar to warm up. We believe this confirms our theory that the feature is actually the result of ice located on the dewar window. During the upcoming Gemini North shutdown period (March 26 - April 2, 2007) GMOS-N will be warmed up and attempts will be made to remove any contaminants from the dewar. We are optimistically expecting this new flatfield feature to therefore disappear. Watch this space for updates in early April!

December 22, 2006
The GMOS-S World Coordinate System has been updated on UT November 28, 2006. With the new WCS, we have improved the large offsets ((RA~5", DEC~4") which has been presented in the the images. The WCS still has offsets of the order of ~0.8"-1.0". Users, please send your feedback about the accuracy of the new GMOS-S WCS since Novembre 28, 2006.

September 12, 2006
On UT September 9, 2006 the GMOS-N World Coordinate System was updated. The WCS is still only a first order correction (pixel scale and rotation) but we believe we have improved the large (~5") offset which has been present in GMOS-N images prior to this and the pixel scale has been improved. The WCS will still have offsets which should be on the order of ~1", we believe these errors originate not from the WCS calibration but from remaining errors in the OIWFS probe mapping (steps to improve the GMOS OIWFS probe mapping are continuing for both GMOS-N and GMOS-S - watch this space for updates). The WCS for GMOS-S is expected to be similarly updated shortly. We are interested in feedback from users as to the accuracy of the GMOS-N WCS since September 9, 2006.

August 30, 2006
Since the recent Gemini North shutdown new flatfield features have appeared on GMOS-N. Observers should take care to employ the correct Twilight Flats in order to remove these features from their data. We are investigating their removal and will post updates when available.

August 30, 2006
We are in the process of updating the GCAL configurations and exposure times for GCALflats and CuAr calibrations. The old table will be replaced with the new table including example spectra and more possible GMOS configurations once we have completed this task.

August 30, 2006
We have recently discovered that GMOS spectra suffer from scattered light which we believe originates from the classically ruled diffraction gratings. Information as to how much scattered light as a function of wavelength for each grating will be made available here as we progress with the characterization.

14 March 2002
GMOS science observations during semester 2001B and update on the current status of GMOS.

27 September 2001
Example images and MOS spectra obtained during GMOS commissioning.

25 September 2001
Excellent progress with GMOS commissioning; update on system verification

Last update October 25, 2007; Kathy Roth