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.

 

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.).