European Southern Observatory
New Technology Telescope

General :
Observations :

MOS Operations

1 Multi Object Spectroscopy system

1.1 Global functionality
1.2 Operation Steps
1.3 Available punch heads
1.4 Safety Measures

1.1 Global functionality

The MOS sub-system in EMMI is a piece of equipment that is capable of punching a serie of slits on a MOS plate, in order to only let through light from certain parts of the field.

These slits can be of different sizes (width & length) according to the observation requirements.

The punching machine is located inside EMMI so that it can punch any plate installed on the starplate wheel. Chronologically, a virgin plate is installed moving the wheel to load position, then the wheel goes to punching position and finally to observing position.

The starplate wheel is able to hold up to 4 different MOS plates, positions marked 2 to 5.

1.2 Operation Steps

The following steps are necessary to do a MOS plate observation:

Take an exposure of the observation field of interest.
Using Midas emos context, mark down the places on the exposure where the slits are desired and create a file containing the corresponding punch positions.
Physically mount an empty plate on a given position of the MOS starplate.
From EMMI OS GUI call up the MOS tool GUI.
Load the file containing the punch positions.
Punch the plate
Take an exposure to check that the plate has been correctly punched.

At that point the plate is ready to be used for the scientific observations.

1.3 Available punch heads

Table 1 : MOS punching heads characteristics

Punch Id	width (microns)	height (microns)	width (arcsec)	height (arcsec)
#1	150	1000	0.80	5.3
#4	190	1600	1.02	8.6
#6 & #7	249	1600	1.34	8.6
#3	350	1590	1.87	8.5

1.4 Safety Measures

Don't remove a punched MOS plate from the starplate wheel if this plate will eventually be used again. If removed the alignment will be lost.
Make sure that the punching head installed is the one that is intended to be used, and that its configuration parameters are set up properly.
Before trying a MOS plate operation, make sure that EMMI configuration corresponds to reality. It is reminded that only MOS plates should be declared as punchable.

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Send comments to: Gabriel Martin <gmartin@eso.org>
Last Update: Feb. 06, 2000 (GM/EC)