A mass \( 0.9 \, \text{kg} \), attached to a horizontal spring, executes SHM with an amplitude \( A_{1} \). When this mass passes through its mean position, then a smaller mass of \( 124 \, \text{g} \) is placed over it and both masses move together with amplitude \( A_{2} \). If the ratio \( {A_{1}}/{A_{2}} \) is \( \dfrac{\alpha}{\alpha - 1} \), then the value of \( \alpha \) will be ______.