I ported John Chapman's Pseudo Lens flares: john-chapman-graphics.blogspot.fr/2013/0...eudo-lens-flare.html
Simple port, except maybe more control over the shader itself, there's no much more than the original.
The only thing I changed is the threshold function, to allow a soft knee (luminance mask will gradually fade from to 0 to 1 instead of being sharp)
Screenshots from Space Engine:
I'd like to have it inserted with the MasterEffect if possible, I tried it myself but honestly the file's too huge and I'm kinda lost in it ^^