diff --git a/CMakeLists.txt b/CMakeLists.txt
index 51ed7f5..efb3a0c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -307,6 +307,7 @@ endif()
 
 set(PUBLICHEADERS
     include/aare/ArrayExpr.hpp
+    include/aare/CalculateEta.hpp
     include/aare/Cluster.hpp
     #include/aare/ClusterFinder.hpp
     include/aare/ClusterFile.hpp
@@ -331,7 +332,6 @@ set(PUBLICHEADERS
     include/aare/RawSubFile.hpp
     #include/aare/VarClusterFinder.hpp
     include/aare/utils/task.hpp
-
 )
 
 
@@ -362,8 +362,6 @@ target_include_directories(aare_core PUBLIC
     "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>" PRIVATE ${lmfit_SOURCE_DIR}/lib
 )
 
-
-
 target_link_libraries(
     aare_core 
     PUBLIC 
diff --git a/benchmarks/calculateeta_benchmark.cpp b/benchmarks/calculateeta_benchmark.cpp
index dc7cd91..609ce89 100644
--- a/benchmarks/calculateeta_benchmark.cpp
+++ b/benchmarks/calculateeta_benchmark.cpp
@@ -1,3 +1,4 @@
+#include "aare/CalculateEta.hpp"
 #include "aare/ClusterFile.hpp"
 #include <benchmark/benchmark.h>
 
diff --git a/include/aare/ClusterFile.hpp b/include/aare/ClusterFile.hpp
index e9530f6..289647d 100644
--- a/include/aare/ClusterFile.hpp
+++ b/include/aare/ClusterFile.hpp
@@ -9,40 +9,6 @@
 
 namespace aare {
 
-typedef enum {
-    cBottomLeft = 0,
-    cBottomRight = 1,
-    cTopLeft = 2,
-    cTopRight = 3
-} corner;
-
-typedef enum {
-    pBottomLeft = 0,
-    pBottom = 1,
-    pBottomRight = 2,
-    pLeft = 3,
-    pCenter = 4,
-    pRight = 5,
-    pTopLeft = 6,
-    pTop = 7,
-    pTopRight = 8
-} pixel;
-
-// TODO: maybe template this!!!!!! why int32_t????
-struct Eta2 {
-    double x;
-    double y;
-    int c;
-    int32_t sum;
-};
-
-struct ClusterAnalysis {
-    uint32_t c;
-    int32_t tot;
-    double etax;
-    double etay;
-};
-
 /*
 Binary cluster file. Expects data to be layed out as:
 int32_t frame_number
@@ -126,29 +92,6 @@ class ClusterFile {
     void close();
 };
 
-int analyze_data(int32_t *data, int32_t *t2, int32_t *t3, char *quad,
-                 double *eta2x, double *eta2y, double *eta3x, double *eta3y);
-int analyze_cluster(Cluster<int32_t, 3, 3> &cl, int32_t *t2, int32_t *t3,
-                    char *quad, double *eta2x, double *eta2y, double *eta3x,
-                    double *eta3y);
-
-// template <typename ClusterType,
-// typename = std::enable_if_t<is_cluster_v<ClusterType>>>
-// NDArray<double, 2> calculate_eta2(ClusterVector<ClusterType> &clusters);
-
-// TODO: do we need rquire clauses?
-// template <typename T> Eta2 calculate_eta2(const Cluster<T, 3, 3> &cl);
-
-// template <typename T> Eta2 calculate_eta2(const Cluster<T, 2, 2> &cl);
-
-// template <typename ClusterType, std::enable_if_t<is_cluster_v<ClusterType>>>
-// Eta2 calculate_eta2(const ClusterType &cl);
-
-// template <typename T, uint8_t ClusterSizeX, uint8_t ClusterSizeY,
-// typename CoordType>
-// Eta2 calculate_eta2(
-// const Cluster<T, ClusterSizeX, ClusterSizeY, CoordType> &cl);
-
 template <typename ClusterType, typename Enable>
 ClusterFile<ClusterType, Enable>::ClusterFile(
     const std::filesystem::path &fname, size_t chunk_size,
@@ -374,160 +317,4 @@ ClusterVector<ClusterType> ClusterFile<ClusterType, Enable>::read_frame() {
     return clusters;
 }
 
-template <typename ClusterType, std::enable_if_t<is_cluster_v<ClusterType>>>
-NDArray<double, 2> calculate_eta2(const ClusterVector<ClusterType> &clusters) {
-    // TOTO! make work with 2x2 clusters
-    NDArray<double, 2> eta2({static_cast<int64_t>(clusters.size()), 2});
-
-    for (size_t i = 0; i < clusters.size(); i++) {
-        auto e = calculate_eta2(clusters.at(i));
-        eta2(i, 0) = e.x;
-        eta2(i, 1) = e.y;
-    }
-
-    return eta2;
-}
-
-/**
- * @brief Calculate the eta2 values for a generic sized cluster and return them
- * in a Eta2 struct containing etay, etax and the index of the respective 2x2
- * subcluster.
- */
-template <typename T, uint8_t ClusterSizeX, uint8_t ClusterSizeY,
-          typename CoordType>
-Eta2 calculate_eta2(
-    const Cluster<T, ClusterSizeX, ClusterSizeY, CoordType> &cl) {
-    Eta2 eta{};
-
-    // TODO loads of overhead for a 2x2 clsuter maybe keep 2x2 calculation
-    constexpr size_t num_2x2_subclusters =
-        (ClusterSizeX - 1) * (ClusterSizeY - 1);
-    std::array<T, num_2x2_subclusters> sum_2x2_subcluster;
-    for (size_t i = 0; i < ClusterSizeY - 1; ++i) {
-        for (size_t j = 0; j < ClusterSizeX - 1; ++j)
-            sum_2x2_subcluster[i * (ClusterSizeX - 1) + j] =
-                cl.data[i * ClusterSizeX + j] +
-                cl.data[i * ClusterSizeX + j + 1] +
-                cl.data[(i + 1) * ClusterSizeX + j] +
-                cl.data[(i + 1) * ClusterSizeX + j + 1];
-    }
-
-    auto c =
-        std::max_element(sum_2x2_subcluster.begin(), sum_2x2_subcluster.end()) -
-        sum_2x2_subcluster.begin();
-
-    eta.sum = sum_2x2_subcluster[c];
-
-    size_t index_bottom_left_max_2x2_subcluster =
-        (int(c / (ClusterSizeX - 1))) * ClusterSizeX + c % (ClusterSizeX - 1);
-
-    if ((cl.data[index_bottom_left_max_2x2_subcluster] +
-         cl.data[index_bottom_left_max_2x2_subcluster + 1]) != 0)
-        eta.x = static_cast<double>(
-                    cl.data[index_bottom_left_max_2x2_subcluster + 1]) /
-                (cl.data[index_bottom_left_max_2x2_subcluster] +
-                 cl.data[index_bottom_left_max_2x2_subcluster + 1]);
-
-    if ((cl.data[index_bottom_left_max_2x2_subcluster] +
-         cl.data[index_bottom_left_max_2x2_subcluster + ClusterSizeX]) != 0)
-        eta.y =
-            static_cast<double>(
-                cl.data[index_bottom_left_max_2x2_subcluster + ClusterSizeX]) /
-            (cl.data[index_bottom_left_max_2x2_subcluster] +
-             cl.data[index_bottom_left_max_2x2_subcluster + ClusterSizeX]);
-
-    eta.c = c; // TODO only supported for 2x2 and 3x3 clusters -> at least no
-               // underyling enum class
-    return eta;
-}
-
-/**
- * @brief Calculate the eta2 values for a 3x3 cluster and return them in a Eta2
- * struct containing etay, etax and the corner of the cluster.
- */
-
-template <typename T> Eta2 calculate_eta2(const Cluster<T, 3, 3> &cl) {
-    Eta2 eta{};
-
-    std::array<T, 4> tot2;
-    tot2[0] = cl.data[0] + cl.data[1] + cl.data[3] + cl.data[4];
-    tot2[1] = cl.data[1] + cl.data[2] + cl.data[4] + cl.data[5];
-    tot2[2] = cl.data[3] + cl.data[4] + cl.data[6] + cl.data[7];
-    tot2[3] = cl.data[4] + cl.data[5] + cl.data[7] + cl.data[8];
-
-    auto c = std::max_element(tot2.begin(), tot2.end()) - tot2.begin();
-    eta.sum = tot2[c];
-    switch (c) {
-    case cBottomLeft:
-        if ((cl.data[3] + cl.data[4]) != 0)
-            eta.x = static_cast<double>(cl.data[4]) / (cl.data[3] + cl.data[4]);
-        if ((cl.data[1] + cl.data[4]) != 0)
-            eta.y = static_cast<double>(cl.data[4]) / (cl.data[1] + cl.data[4]);
-        eta.c = cBottomLeft;
-        break;
-    case cBottomRight:
-        if ((cl.data[2] + cl.data[5]) != 0)
-            eta.x = static_cast<double>(cl.data[5]) / (cl.data[4] + cl.data[5]);
-        if ((cl.data[1] + cl.data[4]) != 0)
-            eta.y = static_cast<double>(cl.data[4]) / (cl.data[1] + cl.data[4]);
-        eta.c = cBottomRight;
-        break;
-    case cTopLeft:
-        if ((cl.data[7] + cl.data[4]) != 0)
-            eta.x = static_cast<double>(cl.data[4]) / (cl.data[3] + cl.data[4]);
-        if ((cl.data[7] + cl.data[4]) != 0)
-            eta.y = static_cast<double>(cl.data[7]) / (cl.data[7] + cl.data[4]);
-        eta.c = cTopLeft;
-        break;
-    case cTopRight:
-        if ((cl.data[5] + cl.data[4]) != 0)
-            eta.x = static_cast<double>(cl.data[5]) / (cl.data[5] + cl.data[4]);
-        if ((cl.data[7] + cl.data[4]) != 0)
-            eta.y = static_cast<double>(cl.data[7]) / (cl.data[7] + cl.data[4]);
-        eta.c = cTopRight;
-        break;
-    }
-    return eta;
-}
-
-template <typename T> Eta2 calculate_eta2(const Cluster<T, 2, 2> &cl) {
-    Eta2 eta{};
-
-    eta.x = static_cast<double>(cl.data[1]) / (cl.data[0] + cl.data[1]);
-    eta.y = static_cast<double>(cl.data[2]) / (cl.data[0] + cl.data[2]);
-    eta.sum = cl.data[0] + cl.data[1] + cl.data[2] + cl.data[3];
-    eta.c = cBottomLeft; // TODO! This is not correct, but need to put something
-    return eta;
-}
-
-// calculates Eta3 for 3x3 cluster based on code from analyze_cluster
-// TODO only supported for 3x3 Clusters
-template <typename T> Eta2 calculate_eta3(const Cluster<T, 3, 3> &cl) {
-
-    Eta2 eta{};
-
-    T sum = 0;
-
-    std::for_each(std::begin(cl.data), std::end(cl.data),
-                  [&sum](T x) { sum += x; });
-
-    eta.sum = sum;
-
-    eta.c = corner::cBottomLeft;
-
-    if ((cl.data[3] + cl.data[4] + cl.data[5]) != 0)
-
-        eta.x = static_cast<double>(-cl.data[3] + cl.data[3 + 2]) /
-
-                (cl.data[3] + cl.data[4] + cl.data[5]);
-
-    if ((cl.data[1] + cl.data[4] + cl.data[7]) != 0)
-
-        eta.y = static_cast<double>(-cl.data[1] + cl.data[2 * 3 + 1]) /
-
-                (cl.data[1] + cl.data[4] + cl.data[7]);
-
-    return eta;
-}
-
 } // namespace aare
diff --git a/include/aare/ClusterVector.hpp b/include/aare/ClusterVector.hpp
index ec0fa40..0e47b51 100644
--- a/include/aare/ClusterVector.hpp
+++ b/include/aare/ClusterVector.hpp
@@ -30,8 +30,7 @@ template <typename T, uint8_t ClusterSizeX, uint8_t ClusterSizeY,
           typename CoordType>
 class ClusterVector<Cluster<T, ClusterSizeX, ClusterSizeY, CoordType>> {
     using value_type = T;
-    // size_t m_cluster_size_x;
-    // size_t m_cluster_size_y;
+
     std::byte *m_data{};
     size_t m_size{0};
     size_t m_capacity;
@@ -155,30 +154,32 @@ class ClusterVector<Cluster<T, ClusterSizeX, ClusterSizeY, CoordType>> {
      * @throws std::runtime_error if the cluster size is not 3x3
      * @warning Only 3x3 clusters are supported for the 2x2 sum.
      */
-    std::vector<T> sum_2x2() {
-        std::vector<T> sums(m_size);
-        const size_t stride = item_size();
+    /* only needed to calculate eta
+        std::vector<T> sum_2x2() {
+            std::vector<T> sums(m_size);
+            const size_t stride = item_size();
 
-        if (ClusterSizeX != 3 || ClusterSizeY != 3) {
-            throw std::runtime_error(
-                "Only 3x3 clusters are supported for the 2x2 sum.");
+            if (ClusterSizeX != 3 || ClusterSizeY != 3) {
+                throw std::runtime_error(
+                    "Only 3x3 clusters are supported for the 2x2 sum.");
+            }
+            std::byte *ptr = m_data + 2 * sizeof(CoordType); // skip x and y
+
+            for (size_t i = 0; i < m_size; i++) {
+                std::array<T, 4> total;
+                auto T_ptr = reinterpret_cast<T *>(ptr);
+                total[0] = T_ptr[0] + T_ptr[1] + T_ptr[3] + T_ptr[4];
+                total[1] = T_ptr[1] + T_ptr[2] + T_ptr[4] + T_ptr[5];
+                total[2] = T_ptr[3] + T_ptr[4] + T_ptr[6] + T_ptr[7];
+                total[3] = T_ptr[4] + T_ptr[5] + T_ptr[7] + T_ptr[8];
+
+                sums[i] = *std::max_element(total.begin(), total.end());
+                ptr += stride;
+            }
+
+            return sums;
         }
-        std::byte *ptr = m_data + 2 * sizeof(CoordType); // skip x and y
-
-        for (size_t i = 0; i < m_size; i++) {
-            std::array<T, 4> total;
-            auto T_ptr = reinterpret_cast<T *>(ptr);
-            total[0] = T_ptr[0] + T_ptr[1] + T_ptr[3] + T_ptr[4];
-            total[1] = T_ptr[1] + T_ptr[2] + T_ptr[4] + T_ptr[5];
-            total[2] = T_ptr[3] + T_ptr[4] + T_ptr[6] + T_ptr[7];
-            total[3] = T_ptr[4] + T_ptr[5] + T_ptr[7] + T_ptr[8];
-
-            sums[i] = *std::max_element(total.begin(), total.end());
-            ptr += stride;
-        }
-
-        return sums;
-    }
+    */
 
     /**
      * @brief Return the number of clusters in the vector
diff --git a/src/Interpolator.cpp b/src/Interpolator.cpp
index d95405a..1c4a385 100644
--- a/src/Interpolator.cpp
+++ b/src/Interpolator.cpp
@@ -1,4 +1,5 @@
 #include "aare/Interpolator.hpp"
+#include "aare/CalculateEta.hpp"
 #include "aare/algorithm.hpp"
 
 namespace aare {