RS Oph in 1933. This eruption is well observed, both in the blue (diamonds, all from Harvard) and visual (circles, all from AAVSO). The large circles from days 40–98 and 239–324 are for 3-day averages of AAVSO data. Two Harvard plates were fortuitously low in the rise and one at the peak, so that we have a good measure of the rise time, which is the last three magnitudes of the rise in 0.9 days. Note that the post-eruption dip has the same B − V color as does the red giant companion star.