GMOS North Filters

The GMOS filters u', g', r', i' and z' are similar to the filters used by the Sloan Digital Sky Survey (SDSS). A description of the SDSS photometric system is presented in Fukugita et al. (1996, AJ, 111, 1748). See the description of optical photometric standard stars for details on the photometric standard calibration. Please note that due to filter degradation discovered in semester 2004A the u' filter is no longer available for science use on GMOS-N. At this time there are no plans to replace the damaged filter.

The filter CaT is a 150nm broad-band filter approximately centered on the Ca Triplet.

The filters Ha and HaC are narrow-band filters for H-alpha and H-alpha continuum, respectively.

The filter DS920 is a narrow-band filter center of a wavelength region of very low sky background.

The filters GG455, OG515 and RG615 are 5mm thick Schott glass filters. These are long-pass filters which can be used to block 2nd-order contamination of the spectra or limit the wavelength range to allow multiple slit-banks in the multi-aperture mode.

Transmission curves based on lab measurements are available for the filters.

The table list the properties of the filters based on laboratory measurements. The wavelength interval given in the tables is the interval within which the transmission is larger than 50 per cent. For the long-pass filters and the filter z_G0304 the wavelength at the 50 per cent transmission at short wavelength edge is given.

Some of the filters can be combined, the allowed combinations are listed last in the table. The combinations are useful for using the IFU in 2 slit mode with the higher dispersion gratings, e.g. R831_G5302 with the filter combination r_G0303 + RG610_G0307.

Imaging with GMOS requires use of either a color filter (griz, CaT) or a narrow band filter. The long-pass filters GG455, OG515, and RG615 are not suitable for imaging. Also imaging without a filter is not available.

Users may supply their own filters for queue observations; see filter policy and specifications for details.

Last update August 24, 2004; Kathy Roth
Previous Version February 26, 2003; Inger Jørgensen