Ans: Use this formula to approximate the value of capacitors needed:
CL=((C1 x C2) / (C1 + C2)) + C stray
C stray is the stray capacitance in the circuit, typically 2-5pF.
If the oscillation frequency is high, the capacitor values should be increased to lower the frequency. If the frequency is low, the capacitor values should be decreased, thus raising the oscillation frequency.
When CL =20pF, C1 and C2 will be approximately 27-33pF each, depending on the amount of stray capacitance.
