Now that you have created a model, it is time to see how well it matches your data.
Pull down the Tools menu and select the Baseline Tool command. This will cause the New Baseline Tool dialogue (Figure 2.4) to appear. This is a standard OSF/Motif selection dialogue that presents you with a list of baselines to choose from. Every baseline that was allowed by the combination of the ANTENNAS and BASELINE adverbs that you used when you started SLIME is shown in a scrolling list.
Figure 2.4: The New Baseline Tool dialogue.
Select a baseline by clicking on it and click on the Apply button to create a baseline tool for the selected baseline. If you get an error message that tells you that there were no data for the selected baseline, try again until you find a baseline that has data.
The baseline tool displays the data for the selected baseline, as shown in Figure 2.5. Amplitude and phase data are plotted in green and the visibilities expected from the current model are plotted in red (Jodrell Bank alumni will recognize the colour scheme used in the OLAF PLOT program). The error bars are calculated from the data weights, which is one reason why it is important to run FIXWT on your data before using SLIME.
If you can not see the model visibilities, you probably need to change the range of displayed amplitudes. Pull down the View menu belonging to the baseline tool and turn off the Autoscale Plots toggle. Then pull down the View menu and select the Amplitude Range command. You will get a dialogue with fields for the maximum and minimum amplitude to be plotted (the initial values reflect the current range): type the values you want into these fields and click on the Apply button. The plot will be rescaled to match the new amplitude range. The procedure for setting the phase range is almost identical.
You can open as many baseline tools as you want. Go back to the New Baseline Tool and create a few more, making sure that you pick baselines with a good range of u, v spacings. You will notice that your screen gets rather cluttered with more than 2 or 3 baseline tools open. You can get rid of the ones you don't want by pulling down the Baseline menu and selecting the Close command or you can iconize them.
Now go back to the model editing tool and make some changes to the model. Note that the model visibilities plotted in the baseline tools will change whenever you make a change. You may also notice that there is a slight delay as the model visibilities are updated. This delay will increase as you open more baseline tools. Individual baselines are plotted in separate tools to discourage you from opening so many baselines that SLIME can't keep up. If you keep the number of baseline tools small to avoid cluttering up your display, you will ensure that SLIME doesn't slow down to an intolerable level.
You should now simplify your model by deleting all of the components except for one sphere. Play around with it a little until the model visibilities are in rough agreement with the data. You don't have to worry about getting them very close since you will use SLIME to search for the set of model parameters that give the best fit to the data in the next section.