diff --git a/loadrunable.cpp b/loadrunable.cpp
index 76ad78c..ead891a 100644
--- a/loadrunable.cpp
+++ b/loadrunable.cpp
@@ -49,7 +49,7 @@ void drawStars(QImage &img, const std::vector<Star> &stars)
     painter.setPen(Qt::red);
     for(auto star : stars)
     {
-        painter.drawEllipse(QPointF(star.m_x, star.m_y), star.m_sx, star.m_sy);
+        painter.drawEllipse(QPointF(star.m_x, star.m_y), star.hw20X(), star.hw20Y());
     }
     img = pix.toImage();
 }
@@ -319,6 +319,8 @@ void LoadRunable::run()
 
             if(m_analyzeLevel>= Stars)
             {
+                double fwhmX = 0;
+                double fwhmY = 0;
                 const int radius = 13;
                 StarFit starFit(radius);
                 std::vector<Star> stars;
@@ -335,10 +337,14 @@ void LoadRunable::run()
                         //printStarModel(radius, r, star);
                         star.m_x += x;
                         star.m_y += y;
+                        fwhmX += star.fwhmX();
+                        fwhmY += star.fwhmY();
                         stars.push_back(star);
                     }
                 }
                 drawStars(img, stars);
+                info.append(StringPair(QObject::tr("FWHM X"), QString::number(fwhmX/stars.size())));
+                info.append(StringPair(QObject::tr("FWHM Y"), QString::number(fwhmY/stars.size())));
             }
             qDebug() << "Star fit" << timer.restart();
         }
diff --git a/starfit.cpp b/starfit.cpp
index aa8c505..197305a 100644
--- a/starfit.cpp
+++ b/starfit.cpp
@@ -182,6 +182,44 @@ bool Star::valid() const
     return !isnan(m_am);
 }
 
+//half width at half maximum = sqrt(2*ln(2))
+double Star::hwhmX() const
+{
+    return 1.177410023*m_sx;
+}
+
+double Star::hwhmY() const
+{
+    return 1.177410023*m_sy;
+}
+
+// half width at 1/20 maximum
+double Star::hw20X() const
+{
+    return 2.447746831*m_sx;
+}
+
+double Star::hw20Y() const
+{
+    return 2.447746831*m_sy;
+}
+
+// full width at half maximum
+double Star::fwhmX() const
+{
+    return 2.354820045*m_sx;
+}
+
+double Star::fwhmY() const
+{
+    return 2.354820045*m_sy;
+}
+
+bool Star::operator<(const Star &d) const
+{
+    return m_am < d.m_am;
+}
+
 StarFit::StarFit(int size)
 {
     m_size = size;
diff --git a/starfit.h b/starfit.h
index 9292fc5..f6ac288 100644
--- a/starfit.h
+++ b/starfit.h
@@ -14,6 +14,13 @@ struct Star
     double m_theta;
     Star();
     bool valid() const;
+    double hwhmX() const;
+    double hwhmY() const;
+    double hw20X() const;
+    double hw20Y() const;
+    double fwhmX() const;
+    double fwhmY() const;
+    bool operator<(const Star &d) const;
 };
 
 class StarFit