Indicative.—The indicative adds the active secondary endings directly to the tense stem ending in -θη- (first aorist) or -η- (second aorist). The inflection is thus like that of the imperfect of a verb in -μι.
a. For -σαν we find -ν from -ν (τ) in poetical and dialectic forms before which η has been shortened to ε ( cross40), thus ὥρμηθεν for ὡρμήθησαν from ὁρμάω
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].