Frequency doubled diode oscillator and fiber amplifier (DOFA) is frequency-stabilized to a hyperfine line of molecular iodine for calcium spectroscopy. The frequency doubling of DOFA is demonstrated using an Mg-doped periodically poled stoichiometric lithium tantalate crystal for generating a 544-nm beam. Saturated absorption spectroscopy is performed on the molecular iodine at 544 nm to find a hyperfine line for stabilizing the 272-nm beam to the calcium-48 transition. Stabilization of the 272-nm beam using the stabilization of the 544-nm beam to the corresponding 127I2 line is discussed.