2.1 FoV in terms of the synthesized beam, $\theta$


$\displaystyle {\rm Bandwidth:} \quad FoV$ $\textstyle \lesssim$ $\displaystyle 0.8 \theta \frac{\nu_0 N_\nu}{BW_{\rm SB}}
\quad {\rm or} \quad \lesssim 0.8 \theta \frac{\nu_0 N_{\rm SB} N_\nu}{BW_{\rm tot}}$  
$\displaystyle {\rm Time:} \quad FoV$ $\textstyle \lesssim$ $\displaystyle \frac{9000}{t_{\rm int}} \theta$ (1)

Here, $N_\nu$ is the number of frequency points per subband and $N_{\rm SB}$ is the number of subbands. A subband can be thought of an IF in aips usage: different upper- or lower-sidebands from each BBC count as subbands, but the number of polarizations does not enter the picture. $BW_{\rm SB}$ is the subband bandwidth; for our station units and correlator, the maximum $BW_{\rm SB}$ is 16MHz (assuming at least Nyquist sampling). $BW_{\rm tot}$ is the total sampled bandwidth ( $=N_{\rm SB} \cdot
BW_{\rm SB}$), $\nu_0$ is the sky frequency (pick lower edge of lowest SB for most conservative estimate), and $t_{\rm int}$ is the integration time. Other parameters have mks units.



\fbox{\usebox{\saveeen}}

The parameters in eq.(1) that can be controlled during correlation are $N_\nu$, $t_{\rm int}$, and $N_{\rm SB}$. The latter will be set in most cases by how you scheduled your experiment (it is possible to correlate subsets of subbands in multiple passes, with approval from the EVN Program Committee), but the first two are entirely independent of the observations and are limited by hardware/software characteristics of the correlator.



campbell@jive.eu