Lunar illumination (percentage) data on an eclipse day needed
I found some chart regarding this, which is here:
http://www.mkrgeo-blog.com/remote-observation-of-the-total-lunar-eclipse/
The light level drops from about 50-60% prenumbral phase. It becomes noticeable.

If you want to get the percentage illumination of the Moon during the eclipse, install the Cartes du Ciel and turn on the Earth's shadow. Then you will be able to gauge the percentage value.
https://xjwfriends.com/2018/02/18/astronomical-diary-vat-4956/