Update README.md

README.md

@@ -5,7 +5,7 @@ beam splitting off-axis zone plate (formerly known as
 transmission zone plate grating TZPG) beams size and position
 at the sample and detector planes for the SCS instrument.
 
-Online installation free version: [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/git/https%3A%2F%2Fgit.xfel.eu%2FSCS%2Fbozcalc/HEAD?filepath=%2Fdoc%2Fsource%2FInteractive%20BOZ%20calculator.ipynb)
+Online installation free version: [![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/git/https%3A%2F%2Fgit.xfel.eu%2FSCS%2Fbozcalc.git/master?labpath=%2Fdoc%2Fsource%2FInteractive%20BOZ%20calculator.ipynb)
 
 
 The online documentation can be found at https://rtd.xfel.eu/docs/bozcalc/en/latest/