Starting in 2008, Haumea’s small moon Namaka has gone through mutual events—occultations and transits—with its parent, based on its 19-day-long orbit. (Haumea itself is on a 283-year-long orbit around the sun.) The events’ dips should be only about 1%, doubled if there is both a transit and a transit of Namaka’s shadow simultaneously, based on the roughly sinusoidal light curve from Haumea itself. Though we tried on several occasions using telescopes from the 5-m Hale reflector at the Palomar Observatory on down, including colleagues using telescopes in India, Armenia, and elsewhere, we have not (yet, as of 2017) succeeded in detecting any of these mutual events. In 2017, rings were discovered around Haumea by groups headed by José Luis Ortiz of Spain and Bruno Secardy of the Paris Observatory.
Brown’s web pages at Caltech describe the importance of detecting the events and what we can learn from them.