From Richard W SCHMUDE Jr
@. . . . . During the past 4 days (Sep. 6 through Sep. 10), I have made several polarimetric and photometric measurements of Mars. The mean polarization of Mars in the Johnson V-filter was +1.69% which indicates a general clearing of the dust; however this value is well below the ~+3.0% which is considered normal (dust free) for Mars at a solar phase angle of 45 degrees. Photometric measurements in the Johnson V-filter show that Mars is about 0.15 magnitudes brighter than predicted which is much less than the 0.3 magnitude difference in July and early August. The B-V value of Mar (Sep. 7 and 10) is 1.56 which is well below the 1.65 to 1.70 value measured in August. Based on all of the polarimetric and photometric measurements made between Sep. 6 and Sep. 10, I conclude that the dust storm clearing has progressed about half-way since the peak in July and August.
Richard W SCHMUDE Jr (PGA , USA)