  We describe the characteristics and performance of a camera system, Spectral
energy distribution Camera for Quasars in Early Universe (SQUEAN). It was
developed to measure SEDs of high redshift quasar candidates (z $\gtrsim$ 5)
and other targets, e.g., young stellar objects, supernovae, and gamma-ray
bursts, and to trace the time variability of SEDs of objects such as active
galactic nuclei (AGNs). SQUEAN consists of an on-axis focal plane camera
module, an auto-guiding system, and mechanical supporting structures. The
science camera module is composed of a focal reducer, a customizable filter
wheel, and a CCD camera on the focal plane. The filter wheel uses filter
cartridges that can house filters with different shapes and sizes, enabling the
filter wheel to hold twenty filters of 50 mm $\times$ 50 mm size, ten filters
of 86 mm $\times$ 86 mm size, or many other combinations. The initial filter
mask was applied to calibrate the filter wheel with high accuracy and we
verified that the filter position is repeatable at much less than one pixel
accuracy. We installed and tested 50 nm medium bandwidth filters of 600 --
1,050 nm and other filters at the commissioning observation in 2015 February.
We found that SQUEAN can reach limiting magnitudes of 23.3 - 25.3 AB mag at
5-$\sigma$ in a 1-hour total integration time. - 25.3 AB mag at 5-$\sigma$ in a
1-hour total integration time.
