diff --git a/shaders/star_frag.glsl b/shaders/star_frag.glsl
index 84ddbb359c..68e7b05e36 100644
--- a/shaders/star_frag.glsl
+++ b/shaders/star_frag.glsl
@@ -44,5 +44,5 @@ void main(void)
     // in fragment shader all points have virtual dimension 1x1, so gl_PointCoord has a value from [0; 1]
     float offset = length((gl_PointCoord.xy - vec2(0.5)) * pointSize);
     float point = (max_theta == -1.0) ? psf_core(offset) : psf_glow(offset);
-    gl_FragColor = vec4(v_color * point, 1.0); // + vec4(0.1, 0.0, 0.0, 0.0); // square for debugging
+    gl_FragColor = vec4(v_color * point, 1.0); // + vec4(0.1, 0.0, 0.0, 0.0); // red square for debugging
 }
diff --git a/shaders/star_vert.glsl b/shaders/star_vert.glsl
index e71c10bed3..803ee16921 100644
--- a/shaders/star_vert.glsl
+++ b/shaders/star_vert.glsl
@@ -9,11 +9,10 @@
 // as published by the Free Software Foundation; either version 2
 // of the License, or (at your option) any later version.
 
-const float a = 0.123; // empirical constant
-
 const float degree_per_px = 0.01; // higher value causes blinking due to optimizations in the psf_glow()
-const float max_square_size = 256.0; // px
-const float max_irradiation = pow((degree_per_px * max_square_size / a), 2.0) / (2.0 * 3.141592653);
+const float max_square_size = 512.0; // px
+const float glow_scale = 0.123; // empirical constant, deg (not to change)
+const float max_irradiation = pow((degree_per_px * max_square_size / glow_scale), 2.0) / (2.0 * 3.141592653);
 
 varying vec3 v_color;
 varying float max_theta;
@@ -25,7 +24,7 @@ attribute float in_PointSize;
 
 const float color_saturation_limit = 0.1; // the ratio of the minimum color component to the maximum
 
-//! Normalizes the color by its green value and corrects extreme saturation
+// Normalizes the color by its green value and corrects extreme saturation
 vec3 green_normalization(vec3 color)
 {
     // color /= max(color.r, max(color.g, color.b)); // we do this in XYZRGBConverter::convertUnnormalized()
@@ -54,8 +53,8 @@ void main(void)
     else
     {
         // Bright light source (glow mode)
-        float irradiation = atan(in_PointSize / max_irradiation) * max_irradiation; // dimmed brightness
-        max_theta = 0.123 * sqrt(irradiation); // emperical glow radius
+        float irradiation = atan(in_PointSize / max_irradiation) * max_irradiation; // dimming
+        max_theta = glow_scale * sqrt(irradiation);
         float half_sq = max_theta / degree_per_px;
         pointSize = 2.0 * half_sq - 1.0;
         v_color = color;
diff --git a/src/celengine/dsorenderer.cpp b/src/celengine/dsorenderer.cpp
index 886bbb474a..d77e657549 100644
--- a/src/celengine/dsorenderer.cpp
+++ b/src/celengine/dsorenderer.cpp
@@ -190,7 +190,7 @@ void DSORenderer::process(DeepSkyObject* const &dso,
         float irradiationEff = astro::magToIrradiance(appMagEff) * exposure;
         if (irradiationEff > labelLowestIrradiation)
         {
-            float distr = irradiationEff / labelLowestIrradiation;
+            float distr = 1.0f - irradiationEff / labelLowestIrradiation;
             labelColor.alpha(distr * labelColor.alpha());
 
             renderer->addBackgroundAnnotation(rep,
diff --git a/src/celengine/starrenderer.cpp b/src/celengine/starrenderer.cpp
index ad83bfe21f..1f6d2fdf48 100644
--- a/src/celengine/starrenderer.cpp
+++ b/src/celengine/starrenderer.cpp
@@ -108,7 +108,7 @@ void StarRenderer::process(const Star& star, float distance, float irradiance)
                     Vector3f starDir = relPos.normalized();
                     if (starDir.dot(viewNormal) > cosFOV)
                     {
-                        float distr = labelLowestIrradiation / irradiation;
+                        float distr = 1.0f - labelLowestIrradiation / irradiation;
                         Color color = Color(Renderer::StarLabelColor, distr * Renderer::StarLabelColor.alpha());
                         renderer->addBackgroundAnnotation(nullptr,
                                                         starDB->getStarName(star, true),