Srila Bhaktisiddhanta Saraswati Thakur Prabhupad About Eclipse Observance

The period of an eclipse is supposed to be inauspicious, according to the opinion of smartas, and so they refrain from all those activities which they normally avoid during any contaminated period. But the devotees who follow the process of regulative devotional service should, if possible, serve the Supreme Lord as usual without caring for such mundane rules.
Before the advent of Sri Gaurasundara, devotees would bathe, etc., during an eclipse. After Mahaprabhu propagated the chanting of the holy names of the Lord, congregational chanting of the holy name of Hari was recommended to be performed at all times, and to do so there is no consideration of proper or improper time. Only those who are busy accumulating piety consider auspicious or inauspicious times. During an eclipse devotees who follow the path of regulative principles do not bathe in the Ganges. In other words, they do not do anything with a desire to attain the result.
Srila Bhaktisiddhanta Saraswati Thakura, letter from Calcutta Gaudiya Math, May 11, 1923.