  In this paper, we investigate the effects of galactic extinction close to the
south galactic pole and plate--to--plate matching errors. These represent the
most probable systematic errors within the Edinburgh/Durham Southern Galaxy
Catalogue (EDSGC) which could affect the angular correlation function. The
distribution of extinction within the EDSGC area was obtained using the Stark
{\it et al.} HI map and the IRAS $100\mu\rm{m}$ flux map. We find that the
amplitude of the whole EDSGC correlation function varies by less than ${\rm
\delta w}=0.003$ for reddening ratios $\rm{R_V}$ in the range
$3.25\rightarrow6$. This corresponds to a range in average extinction of ${\rm
A_B}=0.12\rightarrow0.24$. Simulations were carried out to assess the
contribution to the correlation function from correlated and uncorrelated plate
magnitude errors. The only simulation that affected the large--scale power seen
in \w was for correlated plate errors with a systematic plate--to--plate offset
of ${\rm \Delta m} =0.02$. This represented an overall $0.4$ magnitude
difference between the ends of the EDSGC which was inconsistent with checks
carried out with external photometry. All other simulations had an
insignificant effect on the large--scale form of the correlation function.
These tests suggest that the large--scale power seen in the EDSGC correlation
function is due to intrinsic clustering and is not an artifact of the
construction or location of the catalogue.
