  We demonstrate a broad, flat, visible supercontinuum spectrum that is
generated by a dispersion-engineered tapered photonic crystal fiber pumped by a
1 GHz repetition rate turn-key Ti:sapphire laser outputting $\sim$ 30 fs pulses
at 800 nm. At a pulse energy of 100 pJ, we obtain an output spectrum that is
flat to within 3 dB over the range 490-690 nm with a blue tail extending below
450 nm. The mode-locked laser combined with the photonic crystal fiber forms a
simple visible frequency comb system that is extremely well-suited to the
precise calibration of astrophysical spectrographs, among other applications.
