A notch filter with minimum reflection bandwidth < 20 nm and thermally tunable throughout the visible regime is fabricated using vertically aligned deformed helix ferroelectric liquid crystals. The performance of this filter is characterized both experimentally and theoretically as a tunable Bragg reflection grating. The utility of the filter as a microspectrometer is assessed by recreating the emission spectra of a mercury arc lamp and a liquid crystal display. The recorded performance of the microspectrometer lends it to applications using lower resolution spectral analysis and requiring compact and inexpensive devices such as rapid on-line screening or as disposable sensors.