European Southern Observatory New Technology Telescope

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Astronomy Operations

Instead of creating MOS masks by clicking on every source of a long list, it is much easier and faster to use the automatic mode of EMOS. This procedure describes how to ``fool'' EMOS by replacing the automatically generated table of targets by a user-defined list of sources.

1. Preparation

• Create an ASCII file sources.dat containing your list of sources arranged in five columns: sequence number, X and Y pixel coordinates, magnitude, and class (used by EMOS, best set to 1)
• Create an ASCII file format.fmt to use for the definition of a Midas table and containing:
FS = " "
DEFINE/FIELD R E12.4 :ident
DEFINE/FIELD R E12.4 :x
DEFINE/FIELD R E12.4 :y
DEFINE/FIELD R E12.4 :int
DEFINE/FIELD R E12.4 :class

2. Using EMOS

• Start Midas and load the context EMOS:
kila{guest}[~]: inmidas
Midas 001> create/gui emos
• load the image
• Click on MOS
• Select the desired parameters (slit length, interslit gap, etc...)
• Start the automatic detection with any of the options stars or galaxies. Select any sub-image and magnitude range. Midas creates a list of automatically found targets: bof.tbl
• Replace it by a table containing your sources:
Midas nnn> create/table bof 5 <nrow> sources format
• Use the histogram option to select sources within a range of magnitudes and create a mask
• send mask
• Go on with the next mask, and repeat until the list of sources is exhausted.

Many thanks to Pierre-Alain Duc for finding how to fool EMOS with this procedure!
 

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