A modified Fejér and Jackson summability method with respect to orthogonal polynomials

Let {Pn}n=0∞ be an orthogonal polynomial system on the real line with respect to a measure μμ with compact support SS. Following the classical methods, we define a modified Fejér and Jackson summability method for Fourier series with respect to {Pn}n=0∞. There is a discussion for ultraspherical polynomials. Moreover, we give error estimates for positive summability methods.