Difference: AAOmegaFileFormat (16 vs. 17)

Revision 172009-10-23 - RonHeald

  AAOmega File Format (or, which spectrum is which object?)
  Combining Multiple AAOmega Data Sets containing a Common Subset of Targets
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+Combining of reduced files occurs in 'AUTO' reduction mode when all local object frames have been processed. It also can be done 'manually' using the Combine Reduced Runs... item in the 2dfdr Commands menu.
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+Combining of reduced files occurs in 'Auto Reduction' mode when all local object frames have been processed. It also can be done 'manually' using the Combine Reduced Runs... item in the 2dfdr Commands menu.
 The 2dfdr combine algorithm combines data based on either object name or object location. That is, fibres having the same name (or location) are added and normalised to produce the output. This is to include all objects, whether they are contained within every frame or only a sub-set of the frames. The combine has the following features:
 

 Multiple configurations of the same field can be combined together when objects are in common. Notice this can result in more spectra than the instrument can produce in one exposure.
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+ Only fibre types 'S' (sky) and 'P' (program) fibres are combined. This includes cases in which a fibre has been disabled part way though a field observation, so only good data is combined. Unused/parked fibres have all values set to zero.
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+ Only fibre types 'S' (sky) and 'P' (program) fibres are combined. This includes cases in which a fibre has been disabled part way though a field observation, so only good data is combined. Other fibres such as unused and parked fibres have all values set to zero.
  The first spectra will be all those from the first frame in the combine including unused/parked and sky fibres. Any additional spectra will be only sky and program spectra from objects in subsequent frames and not present in the first frame. If the data combined are all from the same configuration there will be no difference in the fibre count.
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+ All the fibre table extension information is properly propagated. Additional fibres are numbered beginning from the last fibre of the first frame.
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+ All the fibre table extension information is properly propagated. Additional fibres are numbered beginning from the last fibre of the first frame. So for AAOmega, the first 400 fibres will be from the first frame, and fibre 401 and beyond will be additional fibres from subsequent frames (if any).
  Variances are handled properly.
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+N.B. Currently the combined file exposure time is NOT set properly. Exposure time is given in only one place, the value of the FITS header keyword 'EXPOSED'. This exposure time applies to all fibres within the file. When files are combined, this keyword is copied from the first frame. To fix this situation the fibre table structure must be modified to have a new column. This column would give the actual exposure time (in seconds) for each fibre spectrum. See Exposure Time Handling in the bug list.
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+N.B. Currently the combined file exposure time is NOT set properly. Exposure time is given in only one place for a file, the value of FITS header keyword 'EXPOSED'. This exposure time applies to all fibres within the file. When files are combined, this keyword is copied from the first frame - no attempt is made at setting it properly. To fix this situation the fibre table structure must be modified to have a new column. This column would give the actual exposure time (in seconds) for each fibre spectrum. See Exposure Time Handling in the bug list.
  Combining Control 

Control of the combining process is done using the widget on the  2dfdr GUI Combine tab.
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+Selecting whether the combine is done based on matching object name or object location is done with the COMBNAME argument list member. This appears as the Combine Matching Name widget. Setting it to true causes match on name. Setting it false causes the combine to be based on match object locations.
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+Sometimes morons write a script to make a configuration file for a large input catalogue but name the objects randomly (with some non-unique running ID number) rather than naming everything in advance. When this happens the combining should be based on matching object location. This is selected with the COMBNAME argument list member. This appears as the Combine Matching Name widget. Setting it to true causes match on name. Setting it false causes the combine to be based on match object locations.

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