The tables below show the fields of view resulting from various combinations of the parameters in eqs.(2) & (3). Remember, all these numbers are ultimately based on the formulae from Wrobel (1995), so all correspond to a field of view that has no more than a decrease in the response to a point source. If your needs are different, you'll have to adjust the tabulated fields of view accordingly (e.g., see Fig.13-1 in Bridle & Schwab (1989) for a graph of the behavior of the peak response loss due to bandwidth smearing). Here, we consider:
Ttable 2 lists fields of view in arcseconds (via eq.2). The two columns following the configuration description are for km and 8000km, respectively. This helps with determining whether a single correlation pass could map a large enough solid angle on the sky to include all your sources of interest in a given pointing, or whether you'd need multiple correlation passes to get to all your sources (requests for multiple passes should in principle be cleared through the EVN Program Committee during the proposal-review process).
Table 3 lists fields of view as a fraction of a single-dish beam (via eq.3). The two columns following the configuration description are for m and 100m, respectively. This helps to determine whether you can recover, with a single correlation pass, all the sources for which the individual antennas in your array have themselves been able to observe during the pointing. On the other hand, if a given configuration provides a field of view considerably greater than the single-dish beam of the smallest telescope in your array, then there's clearly not much point in using such a large and/or small . If the bandwidth smearing is not a meaningful constraint, you could reduce , possibly ``trading" this for more subbands to get higher sensitivity. If the time smearing is not a meaningful constraint, reducing would in turn reduce the final data size. However, it turns out for our current situation that time smearing will most likely be your limiting factor in trying to map full single-dish beams, as we'll illustrate presently.
The tie between the bandwidth- and time-smearing portions of tables 2 & 3 is the set of valid correlator configurations derivable from eq.(4) -- see also table 1. The maximum limit for 8(16) stations is 2048(512) for s. These assume only one subband and one polarization. Thus not every configuration listed in these tables will necessarily be available for your specific experiment (e.g., any configuration would be ruled out for .
We can see from delving into
table 3 that the time smearing is currently the limiting
factor more often than is bandwidth smearing. Only for shorter-baseline
arrays at the minimum does the time-smearing field of
view approach a full single-dish
beam, whereas there are numerous configurations that provide a bandwidth-smearing
field of view greater than this. The ratio of the two field
of views can be easily computed from eq.(2), with in cm,
in MHz, and in seconds: