CFHT, Instruments, Spectroscopy, GriF, Instrument Description.

GriF Description

Four different modes are offered with the GriF instrument depending on which of the subcomponents are inserted in the beam.

Overview of the system

The three components of GriF are:

The Fabry-Perot Interferoemter

The Fabry Perot offers a spectral resolution of approximately 2000. It is transmissive in H and K, so if used in stand-alone mode (with a narrow band filter), it can be used as a very narrow band filter or to scan emission lines as demonstrated on this picture of OMC-1, obtained in the H2 v=1-0 s(1) line. The unvignetted field of view is then 36" x 36".

The focal plane mask

The focal plane mask contains 9 positions, currently with the following masks: This picture shows the focal plane wheel inside of KIR, with the different positions.

Note: A new mask should be cut soon, so watch for an update of this page. Also, let us know if you have special needs: masks are cut with the LAMA machine, and although it is not a trivial operation, special shaped masks (e.g. a slit with an occulting mask) can be cut if requested at least six weeks in advance.

The Grism cell

The grism cell assembly contains a collimating lens, an imaging lens, a broad K band filter and the grism which allows for a R~400 resolution. It can be used with the long slit in place in the focal plane wheel or with the Fabry Perot and the "GriF mode" masks. Note that Cassegrain Bonnette rotation can be used to change the orientation of the slit on the sky, and that slow differential tracking can be implemented. An example of a long slit exposure on NGC 1068 can be found in the First Images gallery

Possible modes and configurations

To summarize, these three elements can be configured for four general modes:
"GriF observing mode" schematics

Olivier Lai
Last modified: Fri Feb 22 18:18:35 HST