Given a point w in the upper half-plane $$\Pi _{\mathord {+}}$$
Π
+
, we describe the set of all possible values F(w) of transforms $$F(z)\,{:=}\,\int _{[\alpha ,\beta ]}(x-z)^{-1}\sigma (\textrm{d}x)$$
F
(
z
)
:
=
∫
[
α
,
β
]
(
x
-
z
)
-
1
σ
(
d
x
)
, $$z\in \Pi _{\mathord {+}}$$
z
∈
Π
+
, corresponding to solutions $$\sigma $$
σ
to a (non-degenerate) truncated matricial Hausdorff moment problem. This set turns out to be the intersection of two matrix balls the parameters of which are explicitly constructed from the given data.