diff --git a/CMakeLists.txt b/CMakeLists.txt
index d14d213..2dc2433 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -67,3 +67,7 @@ if (GIT_FOUND)
 else()
     message("Git not found - will not rename the exectuable.")
 endif()
+
+# Include header-only library
+target_include_directories(${PROJECT_NAME} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/lib/astro/include)
+
diff --git a/hello.cpp b/hello.cpp
index 104fff2..c61a802 100644
--- a/hello.cpp
+++ b/hello.cpp
@@ -92,8 +92,19 @@ float getTime()
     return timeSpan.count();
 }
 
+#include <vector>
+#include <cmath>
+#include "astro/twoBodyMethods.hpp"
+
 int main()
 {
+    // Calculate period of ISS orbit around the Earth
+    const float semiMajorAxis = 6738000;
+    const float gravitationalParameter = 3.986e14;
+    float period = astro::computeKeplerOrbitalPeriod(semiMajorAxis, gravitationalParameter);
+    period /= 60.0;
+    std::cout << period << std::endl;
+
     // Set up GLFW, OpenGL and GLEW.
     if (!glfwInit())
         return -1;