diff --git a/image_analysis/scale_merge/ScalingResult.cpp b/image_analysis/scale_merge/ScalingResult.cpp
index c01b88e5..83874371 100644
--- a/image_analysis/scale_merge/ScalingResult.cpp
+++ b/image_analysis/scale_merge/ScalingResult.cpp
@@ -40,6 +40,9 @@ void ScalingResult::SaveToFile(const std::string &filename) {
                               "Cannot open " + img_path + " for writing");
     }
 
+    // Header so the columns are self-describing (lines starting with '#' are comments for gnuplot/numpy).
+    img_file << "# image_number scale_G bfactor_Ang2 mosaicity_deg wedge_deg cc_to_merge cc_n\n";
+
     for (size_t i = 0; i < image_scale_g.size(); ++i) {
         img_file << i
                 << " " << image_scale_g[i]