Reliable magnitude difference of Polaris Ab from APO/DSSI speckle data

Derive a reliable magnitude difference between Polaris Aa and Polaris Ab from ARC 3.5-m APO speckle interferometry with DSSI conducted at high airmass, by accurately modeling and correcting atmospheric dispersion and any residual dispersion effects in the Fourier-domain fringe fitting.

Background

The DSSI speckle observations at APO were performed at high airmass, requiring application of a dispersion model and additional free parameters in the fringe fitting to account for residual dispersion in the Fourier domain.

While astrometric positions were obtained, the magnitude difference could not be reliably measured due to the dispersion complications, leaving the photometric contrast of Polaris Ab undetermined in these data.