Dua during the eclipse prayer
اللّهُـمَّ إِنَّ الشَّمسَ وَالقَمَرَ آيَتانِ مِن...
اللّهُـمَّ إِنَّ الشَّمسَ وَالقَمَرَ آيَتانِ مِن آياتِك، لا يَخسِفانِ لِمَوتِ أَحَدٍ وَلا لِحَياتِه، فَإِذا رَأَيتُم ذلِكَ فَادعُوا اللهَ وَكَبِّروا وَصَلُّوا وَتَصَدَّقوا
Allahuma inash-shamsa wal-qamara ayatani min ayatik, la yakhsifani limawti ahadin wala lihayatih, fa-itha ra-aytum thalika fadAAul-laha wakabbiru wasallu wataSaddaqu
Translation
O Allah, the sun and moon are two of Your signs — they do not eclipse due to the death or life of anyone. So when you see that, call upon Allah, say Allahu Akbar, pray and give charity.
When to recite
During a solar or lunar eclipse, hasten to the mosque for Salat al-Kusuf. Make extensive supplication, seek forgiveness (istighfar) and give charity throughout. The Prophet said the eclipse is a reminder of the signs of Allah.
Source / Reference
Al-Bukhari 2/30, Muslim 2/618