N&S Mask Design Change
As of May 14, 2007, the IMACS Mosaic camera has been rotated by 90-deg for future use at the f/2 camera focus. To make N&S multislit observations the grisms are now rotated by 90-deg. You will request this on your Observer Setup Form.
You must make your slitmasks use the latest version of the maskgen — the mask making software. Instructions for designing masks and downloading software to do this are found here. Old N&S masks that you might have planned to use on future observing runs will not work! You must use the latest version of maskgen to remake these. (All the input parameters can be the same, but different Shack-Hartmann and Principal guide stars must be chosen.) The slits for the new mask will run up-down rather than left-right as previous. New masks need to be submitted for cutting per the normal rules.
All future N&S masks will automatically be made this way by selecting the appropriate choice in the intgui (see the latest maskgen instructions).
Observers using f/2 in the regular “stare” mode are not affected by these changes. Their masks, old and new, are fine, and they will produce spectra along the long axes of the CCDs, with fewer CCD gaps per spectrum.
Spectroscopic observations at the IMACS f/4 camera will continue with the Mosaic Camera in N&S orientation.