A 4 in. multilayer mirror telescope has been tested on National Spherical Torus Experiment (NSTX) for high throughput measurements of the beam excited soft x-ray impurity emission. The design is aimed at imaging low- k turbulent fluctuations in the plasma core. The test device used curved and planar MoSi mirrors to focus with ≈15% optical transmission and few angstrom bandwidths, the 135 Å Lyα line from injected Li III atoms, or the n=2-4 line from intrinsic C VI ions. As test detectors we used 1 cm2 absolute extreme ultraviolet diodes, equipped with 400 kHz bandwidth, low noise preamplifiers. With the available view on NSTX the telescope successfully detected small impurity density fluctuations associated with 11 modes rotating at midradius, indicating that a high signal to noise ratio and cost effective core turbulence diagnostic is feasible based on this concept. © 2006 American Institute of Physics.