diff --git a/src/celengine/fisheyeprojectionmode.cpp b/src/celengine/fisheyeprojectionmode.cpp
index 782d5e5e72..c9753eb652 100644
--- a/src/celengine/fisheyeprojectionmode.cpp
+++ b/src/celengine/fisheyeprojectionmode.cpp
@@ -59,7 +59,7 @@ float FisheyeProjectionMode::getFieldCorrection(float /*zoom*/) const
 }
 
 celmath::Frustum
-FisheyeProjectionMode::getFrustum(float nearZ, float farZ, float zoom) const
+FisheyeProjectionMode::getFrustum(float nearZ, std::optional<float> farZ, float zoom) const
 {
     return celmath::Frustum(getFOV(zoom), width / height, nearZ, farZ);
 }
diff --git a/src/celengine/fisheyeprojectionmode.h b/src/celengine/fisheyeprojectionmode.h
index cb3453ca6a..505c53ca0e 100644
--- a/src/celengine/fisheyeprojectionmode.h
+++ b/src/celengine/fisheyeprojectionmode.h
@@ -32,7 +32,7 @@ class FisheyeProjectionMode : public ProjectionMode
     float getZoom(float fov) const override;
     float getPixelSize(float zoom) const override;
     float getFieldCorrection(float zoom) const override;
-    celmath::Frustum getFrustum(float nearZ, float farZ, float zoom) const override;
+    celmath::Frustum getFrustum(float nearZ, std::optional<float> farZ, float zoom) const override;
     double getViewConeAngleMax(float zoom) const override;
 
     float getNormalizedDeviceZ(float nearZ, float farZ, float z) const override;
diff --git a/src/celengine/perspectiveprojectionmode.cpp b/src/celengine/perspectiveprojectionmode.cpp
index bf344077ad..9534dfba2c 100644
--- a/src/celengine/perspectiveprojectionmode.cpp
+++ b/src/celengine/perspectiveprojectionmode.cpp
@@ -56,7 +56,7 @@ float PerspectiveProjectionMode::getFieldCorrection(float zoom) const
 }
 
 celmath::Frustum
-PerspectiveProjectionMode::getFrustum(float nearZ, float farZ, float zoom) const
+PerspectiveProjectionMode::getFrustum(float nearZ, std::optional<float> farZ, float zoom) const
 {
     return celmath::Frustum(getFOV(zoom), width / height, nearZ, farZ);
 }
diff --git a/src/celengine/perspectiveprojectionmode.h b/src/celengine/perspectiveprojectionmode.h
index 8013d9ab29..3176ae8723 100644
--- a/src/celengine/perspectiveprojectionmode.h
+++ b/src/celengine/perspectiveprojectionmode.h
@@ -32,7 +32,7 @@ class PerspectiveProjectionMode : public ProjectionMode
     float getZoom(float fov) const override;
     float getPixelSize(float zoom) const override;
     float getFieldCorrection(float zoom) const override;
-    celmath::Frustum getFrustum(float nearZ, float farZ, float zoom) const override;
+    celmath::Frustum getFrustum(float nearZ, std::optional<float> farZ, float zoom) const override;
     double getViewConeAngleMax(float zoom) const override;
 
     float getNormalizedDeviceZ(float nearZ, float farZ, float z) const override;
diff --git a/src/celengine/projectionmode.h b/src/celengine/projectionmode.h
index 950ee6eaac..ac6d4502fa 100644
--- a/src/celengine/projectionmode.h
+++ b/src/celengine/projectionmode.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include <Eigen/Core>
+#include <optional>
 
 class ShaderManager;
 
@@ -36,7 +37,7 @@ class ProjectionMode
     virtual float getZoom(float fov) const = 0;
     virtual float getPixelSize(float zoom) const = 0;
     virtual float getFieldCorrection(float zoom) const = 0;
-    virtual celmath::Frustum getFrustum(float nearZ, float farZ, float zoom) const = 0;
+    virtual celmath::Frustum getFrustum(float nearZ, std::optional<float> farZ, float zoom) const = 0;
 
     // Calculate the cosine of half the maximum field of view. We'll use this for
     // fast testing of object visibility.
diff --git a/src/celengine/render.cpp b/src/celengine/render.cpp
index c0cbe2e66e..fd1a8a635f 100644
--- a/src/celengine/render.cpp
+++ b/src/celengine/render.cpp
@@ -1531,7 +1531,7 @@ void Renderer::draw(const Observer& observer,
     m_cameraOrientation = Quaterniond(m_cameraTransform) * observer.getOrientation();
 
     // Get the view frustum used for culling in camera space.
-    auto frustum = projectionMode->getFrustum(MinNearPlaneDistance, std::numeric_limits<float>::infinity(), zoom);
+    auto frustum = projectionMode->getFrustum(MinNearPlaneDistance, std::nullopt, zoom);
 
     // Get the transformed frustum, used for culling in the astrocentric coordinate
     // system.
@@ -3939,7 +3939,7 @@ void Renderer::renderDeepSkyObjects(const Universe& universe,
     dsoRenderer.renderFlags      = renderFlags;
     dsoRenderer.labelMode        = labelMode;
 
-    dsoRenderer.frustum = projectionMode->getFrustum(MinNearPlaneDistance, std::numeric_limits<float>::infinity(), observer.getZoom());
+    dsoRenderer.frustum = projectionMode->getFrustum(MinNearPlaneDistance, std::nullopt, observer.getZoom());
     // Use pixelSize * screenDpi instead of FoV, to eliminate windowHeight dependence.
     // = 1.0 at startup
     float effDistanceToScreen = mmToInches((float) REF_DISTANCE_TO_SCREEN) * pixelSize * getScreenDpi();
diff --git a/src/celmath/frustum.cpp b/src/celmath/frustum.cpp
index fe5a742bf3..df35f71ed4 100644
--- a/src/celmath/frustum.cpp
+++ b/src/celmath/frustum.cpp
@@ -23,16 +23,16 @@ Frustum::Frustum(float fov, float aspectRatio, float n) :
     init(fov, aspectRatio, n, n);
 }
 
-Frustum::Frustum(float fov, float aspectRatio, float n, float f) :
-    infinite(std::isinf(f))
+Frustum::Frustum(float fov, float aspectRatio, float n, std::optional<float> f) :
+    infinite(!f.has_value())
 {
-    init(fov, aspectRatio, n, infinite ? n : f);
+    init(fov, aspectRatio, n, infinite ? n : f.value());
 }
 
-Frustum::Frustum(float l, float r, float t, float b, float n, float f) :
-    infinite(std::isinf(f))
+Frustum::Frustum(float l, float r, float t, float b, float n, std::optional<float> f) :
+    infinite(!f.has_value())
 {
-    init(l, r, t, b, n, infinite ? n : f);
+    init(l, r, t, b, n, infinite ? n : f.value());
 }
 
 void Frustum::init(float fov, float aspectRatio, float n, float f)
diff --git a/src/celmath/frustum.h b/src/celmath/frustum.h
index e379f404d2..939ef34f3d 100644
--- a/src/celmath/frustum.h
+++ b/src/celmath/frustum.h
@@ -12,6 +12,7 @@
 #include <Eigen/Core>
 #include <Eigen/Geometry>
 
+#include <optional>
 
 namespace celmath
 {
@@ -22,8 +23,8 @@ class Frustum
     using PlaneType = Eigen::Hyperplane<float, 3>;
 
     Frustum(float fov, float aspectRatio, float nearDist);
-    Frustum(float fov, float aspectRatio, float nearDist, float farDist);
-    Frustum(float left, float right, float top, float bottom, float nearDist, float farDist);
+    Frustum(float fov, float aspectRatio, float nearDist, std::optional<float> farDist);
+    Frustum(float left, float right, float top, float bottom, float nearDist, std::optional<float> farDist);
 
     inline Eigen::Hyperplane<float, 3> plane(unsigned int which) const
     {