Ending song episode 13 Moretsu Pirates (sub)
With thanks to Memor-X I was pointed to the right direction in order to pinpoint the soundtrack used. Due to it being unavailable in my country I can't get my hands on the original album. I was able to verify this with the instrumental version, preview samples and a non legal version. 

The name of the soundtrack is Toumei na Yozora ~Mabataku Hoshi ni Tsutsumarete~ covered by Komatsu Mikako which had the street release date of April 25th 2012.