Overview of ROMAFOT

The current MIDAS implementation of ROMAFOT consists of 17 commands which are listed in Table 5.3. In order to be able to execute these commands the context ROMAFOT should be enabled first. This can be done using the command SET/CONTEXT ROMAFOT.

 

Table 5.1: ROMAFOT commands

Command	Description
ADAPT/ROMAFOT	Adapt trial values to a new image frame
ADDSTAR/ROMAFOT	Add pre-selected subarrays to the original image frame
ANALYSE/ROMAFOT	Select objects or analyses the results of the fit procedure
CHECK/ROMAFOT	Estimate number and accuracy of artificial objects recovered
CBASE/ROMAFOT	Create the base-line for transformation of frame coordinates
CTRANS/ROMAFOT	Execute transformation of coordinates on intermediate table
DIAPHRAGM/ROMAFOT	Perform aperture photometry
EXAMINE/ROMAFOT	Examine quality of the fitted objects; flags them if needed
FCLEAN/ROMAFOT	Select subarrays containing artificial objects
FIND/ROMAFOT	Select objects from ROMAFOT frame using the image display
FIT/ROMAFOT	Determine characteristics of objects by non-linear fitting
GROUP/ROMAFOT	Perform an automatic grouping of objects
MFIT/ROMAFOT	Fit the PSF using the integral of the PSF (for undersampled data)
MODEL/ROMAFOT	Determine subpixel values to be used for the integral of the PSF
REGISTER/ROMAFOT	Compute absolute parameters and stores results in final table
RESIDUAL/ROMAFOT	Compute difference between original and reconstructed image
SEARCH/ROMAFOT	Perform actual search of object above certain threshold
SELECT/ROMAFOT	Select objects or stores parameters in intermediate table
SKY/ROMAFOT	Determine intensity histogram and background in selected areas

 

ROMAFOT is as interactive as the user wishes. In fact, during a reduction session the user is often asked to choose between an interactive or an automatic procedure, including ``greytone'' extremes. Hence, the package leaves it up to the user:

• to select program stars,
• to model the subframes to fit,
• to choose the number of components in each subframe,
• to check the data reconstruction.

For the user one cannot define a fixed set of guidelines for these decisions, apart from the two obvious considerations that no software can take the place of the human brain and that the benefit of photometric precision should be proportional to the cost in terms of human effort.

As stated above, apart from a part which has to be interactive, the user can choose between running ROMAFOT in automatic or in interactive mode. Hence, a number of interactive ROMAFOT commands have non-interactive ``sister'' command(s) with the same functionality. Figure 5.1 shows the flow diagram of the ROMAFOT package. From this diagram it is clear that after determining the PSF one can continue along two paths. Figure 5.2 visualises the procedure to insert artificial stars in the original frame in order to estimate the ability of the program to recover an object and the general reproducibility of the photometry. Finally, Figure 5.3 shows the procedure to use the photometric results (positions and intensities) from the frame with the best resolution as input for all the other program frames.

  

Figure 5.1: Romafot reduction scheme

  

Figure 5.2: Romafot procedure to determine accuracy and degree of completeness

  

Figure 5.3: Romafot procedure to transfer inputs to other program frames

ROMAFOT is fully integrated into the MIDAS environment, which means that the image display part runs on all display system supported by MIDAS and that all intermediate and the final results are stores in MIDAS tables. Obviously, the use of the MIDAS table file system adds a great deal of flexibility to ROMAFOT, since a large number of MIDAS commands can be used (e.g. for table emanupulation, displaying, selection, etc.).