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Optomechanical Layout

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The opto-mechanical layout of FLAMINGOS-2 is shown above. The instrument is fed with either the standard (non-AO) f/16 beam from the secondary, or in the future an MCAO corrected f/32 beam. Light enters the first (MOS) dewar, and comes to a focus at the mask plane.

There is an optical OIWFS which is operated cold (and thus does not glow in the beam) and uses a small pickoff mirror to guide on a 6"x6" field containing the guidestar.

The MOS wheel has slots for 6 longslit masks and 9 custom cut MOS masks, 2 large circular pinhole masks, and an open position for the imaging mode. After the MOS wheel, light passes through a decker wheel and a field lens before passing through an open gate valve into the second (camera) dewar. Here the light is reflected off two flat mirrors before passing through the remainder of the collimator optics, and then the filter and Lyot wheels. Each of the two filter wheels can hold up to four filters, plus an open slot. The Lyot wheel is used to place cold stops in the beam for use at f/32 with MCAO. Light then passes through the grism wheel, with a choice between two low-resolution (R~1200) grisms, a medium-resolution (R~3000) grism, or an open hole (for imaging). Finally the light passes through the six-element camera optics and is focused onto the HAWAII2 detector, with a plate scale of 0.18 arcsec/pixel in non-AO mode, or 0.09 arcsec/pixel with MCAO.

The following is a 3D drawing of the instrument as seen from the telescope (without the MOS dewar cover, the bottom dewar snout, and the OIWFS mechanism). One can clearly see the MOS (foreground and black) and the decker (light green) wheels. This is a non-standard setup in which the MOS has a mask in the beam and the decker wheel is in the OPEN position.

This is a 3D drawing of the instrument as seen from the top. All shields, dewar covers and jackets, and cabling have been removed or rendered transparent. One can see the main elements of the FLAMINGOS-2 camera (mirrors and lens barrels). The external black boxes house the detector electronics. The black round housing in between the lens barrels contains the two filter wheels, the lyot wheel, and the grism wheel. The three small cylinders seen are the wheel drivers.

The imaging and MOS fields of view are shown below, with dimensions in the standard f/16 (non-AO) mode which will be available first.