Hi,
do you know what Window colors are ? Children love them in Germany !
http://www.artsncrafts-ideas.com/kid...s-painting.php
I made a cross wire for my eyepiece with the hair of my wife. But before making the cross, I put some self-lightening window color (for children !!) on a paper and draw the hair through this plot of color.
Now, when I take my torch / flashlight and give a short light input into the eyepiece, the cross-hair is shining - let's say - for one hour without any problem !
Clear Skies
Rudi