To find the absolute magnitude (Mv) using the given period (P = 7), the relevant equation is Mv = -[2.76(log10(P) - 1.0)] - 4.16. The user is seeking assistance in evaluating this equation but lacks a suitable calculator. Forum members suggest using online calculators or smartphone apps that can handle logarithmic functions. It's clarified that the user needs to evaluate the expression rather than solve an equation. The discussion emphasizes the importance of understanding the calculation process and available tools.