diff --git a/include/GEbounds.hpp b/include/GEbounds.hpp
index 00d1e1d..cf0df39 100644
--- a/include/GEbounds.hpp
+++ b/include/GEbounds.hpp
@@ -55,12 +55,12 @@ class GEbounds : public GContainer {
 public:
     // Constructors and destructors
     GEbounds(void);
-    GEbounds(const GEbounds& ebds);
+    explicit GEbounds(const std::string& filename);
     explicit GEbounds(const GXmlElement& xml);
+    GEbounds(const GEbounds& ebds);
     GEbounds(const GEnergy& emin, const GEnergy& emax);
     GEbounds(const int& num, const GEnergy& emin, const GEnergy& emax,
              const bool& log = true);
-    GEbounds(const std::string& filename);
     virtual ~GEbounds(void);
 
     // Operators
diff --git a/include/GEnergies.hpp b/include/GEnergies.hpp
index 3b97cad..b245938 100644
--- a/include/GEnergies.hpp
+++ b/include/GEnergies.hpp
@@ -49,8 +49,7 @@ class GEnergies : public GContainer {
 public:
     // Constructors and destructors
     GEnergies(void);
-    GEnergies(const std::string& filename,
-              const std::string& extname = "ENERGIES");
+    explicit  GEnergies(const std::string& filename);
     GEnergies(const GEnergies& energies);
     GEnergies(const int& num, const GEnergy& emin, const GEnergy& emax,
               const bool& log = true);
@@ -78,11 +77,9 @@ public:
                                            const GEnergy& emax);
     void           set_log(const int& num, const GEnergy& emin,
                                            const GEnergy& emax);
-    void           load(const std::string& filename,
-                        const std::string& extname = "ENERGIES");
+    void           load(const std::string& filename);
     void           save(const std::string& filename,
-                        const bool&        clobber = false,
-                        const std::string& extname = "ENERGIES") const;
+                        const bool&        clobber = false) const;
     void           read(const GFitsTable& table);
     void           write(GFits& file,
                          const std::string& extname = "ENERGIES") const;
diff --git a/include/GGti.hpp b/include/GGti.hpp
index 1477d45..60e5eef 100644
--- a/include/GGti.hpp
+++ b/include/GGti.hpp
@@ -58,6 +58,7 @@ class GGti : public GContainer {
 public:
     // Constructors and destructors
     GGti(void);
+    explicit GGti(const std::string& filename);
     GGti(const GGti& gti);
     GGti(const GTime& tstart, const GTime& tstop);
     explicit GGti(const GXmlElement& xml);
@@ -81,11 +82,9 @@ public:
     void                  remove(const int& index);
     void                  reserve(const int& num);
     void                  extend(const GGti& gti);
-    void                  load(const std::string& filename,
-                               const std::string& extname = "GTI");
+    void                  load(const std::string& filename);
     void                  save(const std::string& filename,
-                               const bool& clobber = false,
-                               const std::string& extname = "GTI") const;
+                               const bool& clobber = false) const;
     void                  read(const GFitsTable& table);
     void                  write(GFits& file,
                                 const std::string& extname = "GTI") const;
diff --git a/include/GNodeArray.hpp b/include/GNodeArray.hpp
index 74d0d87..d764e0b 100644
--- a/include/GNodeArray.hpp
+++ b/include/GNodeArray.hpp
@@ -59,9 +59,10 @@ class GNodeArray : public GContainer {
 public:
     // Constructors and destructors
     GNodeArray(void);
-    GNodeArray(const int& num, const double* array);
+    explicit GNodeArray(const std::string& filename);
     explicit GNodeArray(const GVector& vector);
     explicit GNodeArray(const std::vector<double>& vector);
+    GNodeArray(const int& num, const double* array);
     GNodeArray(const GNodeArray& array);
     virtual ~GNodeArray(void);
 
@@ -93,10 +94,9 @@ public:
     const int&    inx_right(void) const;
     const double& wgt_left(void) const;
     const double& wgt_right(void) const;
-    void          load(const std::string& filename,
-                       const std::string& extname = "NODES");
-    void          save(const std::string& filename, const bool& clobber = false,
-                       const std::string& extname = "NODES") const;
+    void          load(const std::string& filename);
+    void          save(const std::string& filename,
+                       const bool& clobber = false) const;
     void          read(const GFitsTable& table);
     void          write(GFits& file,
                         const std::string& extname = "NODES") const;
diff --git a/inst/cta/include/GCTAPointing.hpp b/inst/cta/include/GCTAPointing.hpp
index cc15738..e2e2904 100644
--- a/inst/cta/include/GCTAPointing.hpp
+++ b/inst/cta/include/GCTAPointing.hpp
@@ -61,8 +61,7 @@ public:
     GCTAPointing(void);
     explicit GCTAPointing(const GSkyDir& dir);
     explicit GCTAPointing(const GXmlElement& xml);
-    GCTAPointing(const std::string& filename,
-                 const std::string& extname = "POINTING");
+    explicit GCTAPointing(const std::string& filename);
     GCTAPointing(const GCTAPointing& pnt);
     virtual ~GCTAPointing(void);
 
@@ -83,8 +82,7 @@ public:
     void           zenith(const double& zenith);  
     void           azimuth(const double& azimuth); 
     GHorizDir      dir_horiz(const GTime& time) const;
-    void           load(const std::string& filename,
-                        const std::string& extname = "POINTING");
+    void           load(const std::string& filename);
     void           read(const GFitsTable& table);
     void           read(const GXmlElement& xml);
     void           write(GXmlElement& xml) const;
diff --git a/inst/cta/pyext/GCTAPointing.i b/inst/cta/pyext/GCTAPointing.i
index 9041191..a152e70 100644
--- a/inst/cta/pyext/GCTAPointing.i
+++ b/inst/cta/pyext/GCTAPointing.i
@@ -40,8 +40,7 @@ public:
     GCTAPointing(void);
     explicit GCTAPointing(const GSkyDir& dir);
     explicit GCTAPointing(const GXmlElement& xml);
-    GCTAPointing(const std::string& filename,
-                 const std::string& extname = "POINTING");
+    explicit GCTAPointing(const std::string& filename);
     GCTAPointing(const GCTAPointing& pnt);
     virtual ~GCTAPointing(void);
 
@@ -59,8 +58,7 @@ public:
     void           zenith(const double& zenith);  
     void           azimuth(const double& azimuth); 
     GHorizDir      dir_horiz(const GTime& time) const;
-    void           load(const std::string& filename,
-                        const std::string& extname = "POINTING");
+    void           load(const std::string& filename);
     void           read(const GFitsTable& table);
     void           read(const GXmlElement& xml);
     void           write(GXmlElement& xml) const;
diff --git a/inst/cta/src/GCTAPointing.cpp b/inst/cta/src/GCTAPointing.cpp
index dc6e411..ebad18e 100644
--- a/inst/cta/src/GCTAPointing.cpp
+++ b/inst/cta/src/GCTAPointing.cpp
@@ -28,8 +28,9 @@
 #ifdef HAVE_CONFIG_H
 #include <config.h>
 #endif
-#include "GCTAPointing.hpp"
 #include "GTools.hpp"
+#include "GFilename.hpp"
+#include "GCTAPointing.hpp"
 #include "GFits.hpp"
 #include "GHorizDir.hpp"
 
@@ -107,21 +108,19 @@ GCTAPointing::GCTAPointing(const GXmlElement& xml)
 
 
 /***********************************************************************//**
- * @brief Pointing table constructor
+ * @brief FITS file constructor
  *
- * @param[in] filename Pointing table file.
- * @param[in] extname Pointing extension name (defaults to "POINTING")
+ * @param[in] filename FITS file.
  *
- * Construct CTA pointing from a pointing table file.
+ * Construct CTA pointing from a pointing table FITS file.
  ***************************************************************************/
-GCTAPointing::GCTAPointing(const std::string& filename,
-                           const std::string& extname)
+GCTAPointing::GCTAPointing(const std::string& filename)
 {
     // Initialise members
     init_members();
 
     // Load pointing table
-    load(filename, extname);
+    load(filename);
 
     // Return
     return;
@@ -400,24 +399,28 @@ GHorizDir GCTAPointing::dir_horiz(const GTime& time) const
 
 
 /************************************************************************
- * @brief Load pointing table from a pointing file
+ * @brief Load pointings from a FITS file
  *
- * @param[in] filename Pointing table filename.
- * @param[in] extname Pointing extension name (defaults to "POINTING")
+ * @param[in] filename FITS file name.
+ *
+ * Loads pointings from a pointing table FITS file.
  *
- * Loads a pointing table from a FITS file. See the read() method for
- * more information about the structure of the FITS file.
+ * If no extension name is provided, the pointing is are loaded from the
+ * "POINTING" extension.
  ************************************************************************/
-void GCTAPointing::load(const std::string& filename, const std::string& extname)
+void GCTAPointing::load(const std::string& filename)
 {
+    // Create file name
+    GFilename fname(filename);
+
     // Allocate FITS file
     GFits file;
 
     // Open FITS file
-    file.open(filename);
+    file.open(fname.filename());
 
     // Get pointing table
-    const GFitsTable& table = *file.table(extname);
+    const GFitsTable& table = *file.table(fname.extname("POINTING"));
 
     // Read pointing from table
     read(table);
@@ -431,7 +434,7 @@ void GCTAPointing::load(const std::string& filename, const std::string& extname)
 
 
 /************************************************************************
- * @brief Load pointing table from a pointing file
+ * @brief Read pointings from a FITS table
  *
  * @param[in] filename Pointing table filename.
  * @param[in] extname Pointing extension name (defaults to "POINTING")
diff --git a/inst/mwl/include/GMWLObservation.hpp b/inst/mwl/include/GMWLObservation.hpp
index e08822c..dace35f 100644
--- a/inst/mwl/include/GMWLObservation.hpp
+++ b/inst/mwl/include/GMWLObservation.hpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *        GMWLObservation.hpp - Multi-wavelength observation class         *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2014 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -49,8 +49,6 @@ public:
     // Constructors and destructors
     GMWLObservation(void);
     explicit GMWLObservation(const std::string& filename);
-    explicit GMWLObservation(const std::string& filename, const int& extno);
-    explicit GMWLObservation(const std::string& filename, const std::string& extname);
     GMWLObservation(const GMWLObservation& obs);
     virtual ~GMWLObservation(void);
 
@@ -73,8 +71,6 @@ public:
 
     // Other methods
     void               load(const std::string& filename);
-    void               load(const std::string& filename, const int& extno);
-    void               load(const std::string& filename, const std::string& extname);
     const std::string& filename(void) const;
     const std::string& extno(void) const;
     const std::string& extname(void) const;
diff --git a/inst/mwl/include/GMWLSpectrum.hpp b/inst/mwl/include/GMWLSpectrum.hpp
index f54d3a4..1eb84f6 100644
--- a/inst/mwl/include/GMWLSpectrum.hpp
+++ b/inst/mwl/include/GMWLSpectrum.hpp
@@ -74,8 +74,6 @@ public:
     virtual std::string   print(const GChatter& chatter = NORMAL) const;
 
     // Other methods
-    void               load(const std::string& filename, const std::string& extname);
-    void               load(const std::string& filename, const int& extno);
     void               read(const GFits& file, const std::string& extname);
     void               read(const GFits& file, const int& extno);
     const std::string& telescope(void) const;
diff --git a/inst/mwl/pyext/GMWLObservation.i b/inst/mwl/pyext/GMWLObservation.i
index da6c7da..61d7b7c 100644
--- a/inst/mwl/pyext/GMWLObservation.i
+++ b/inst/mwl/pyext/GMWLObservation.i
@@ -1,7 +1,7 @@
 /***************************************************************************
  *         GMWLObservation.i - Multi-wavelength observation class          *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2014 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -39,12 +39,11 @@
  * instrument. The spectral points are given in physical units.
  ***************************************************************************/
 class GMWLObservation : public GObservation {
+
 public:
     // Constructors and destructors
     GMWLObservation(void);
     explicit GMWLObservation(const std::string& filename);
-    explicit GMWLObservation(const std::string& filename, const int& extno);
-    explicit GMWLObservation(const std::string& filename, const std::string& extname);
     GMWLObservation(const GMWLObservation& obs);
     virtual ~GMWLObservation(void);
 
@@ -63,8 +62,6 @@ public:
 
     // Other methods
     void               load(const std::string& filename);
-    void               load(const std::string& filename, const int& extno);
-    void               load(const std::string& filename, const std::string& extname);
     const std::string& filename(void) const;
     const std::string& extno(void) const;
     const std::string& extname(void) const;
diff --git a/inst/mwl/pyext/GMWLSpectrum.i b/inst/mwl/pyext/GMWLSpectrum.i
index f89ea48..d93e09e 100644
--- a/inst/mwl/pyext/GMWLSpectrum.i
+++ b/inst/mwl/pyext/GMWLSpectrum.i
@@ -57,8 +57,6 @@ public:
     virtual int           number(void) const;
 
     // Other methods
-    void               load(const std::string& filename, const std::string& extname);
-    void               load(const std::string& filename, const int& extno);
     void               read(const GFits& file, const std::string& extname);
     void               read(const GFits& file, const int& extno);
     const std::string& telescope(void) const;
diff --git a/inst/mwl/src/GMWLObservation.cpp b/inst/mwl/src/GMWLObservation.cpp
index 92e1a11..1f01cad 100644
--- a/inst/mwl/src/GMWLObservation.cpp
+++ b/inst/mwl/src/GMWLObservation.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *         GMWLObservation.cpp - Multi-wavelength observation class        *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2013 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -28,8 +28,9 @@
 #ifdef HAVE_CONFIG_H
 #include <config.h>
 #endif
-#include "GObservationRegistry.hpp"
 #include "GTools.hpp"
+#include "GFilename.hpp"
+#include "GObservationRegistry.hpp"
 #include "GException.hpp"
 #include "GMWLObservation.hpp"
 #include "GMWLSpectrum.hpp"
@@ -93,50 +94,6 @@ GMWLObservation::GMWLObservation(const std::string& filename) : GObservation()
 
 
 /***********************************************************************//**
- * @brief File constructor
- *
- * @param[in] filename File name.
- * @param[in] extno FITS file extension number.
- *
- * Creates instance from file.
- ***************************************************************************/
-GMWLObservation::GMWLObservation(const std::string& filename,
-                                 const int& extno) : GObservation()
-{
-    // Initialise members
-    init_members();
-
-    // Load observation
-    load(filename, extno);
-
-    // Return
-    return;
-}
-
-
-/***********************************************************************//**
- * @brief File constructor
- *
- * @param[in] filename File name.
- * @param[in] extname FITS file extension name.
- *
- * Creates instance from file.
- ***************************************************************************/
-GMWLObservation::GMWLObservation(const std::string& filename,
-                                 const std::string& extname) : GObservation()
-{
-    // Initialise members
-    init_members();
-
-    // Load observation
-    load(filename, extname);
-
-    // Return
-    return;
-}
-
-
-/***********************************************************************//**
  * @brief Copy constructor
  *
  * @param[in] obs Observation.
@@ -336,11 +293,11 @@ void GMWLObservation::read(const GXmlElement& xml)
             
             // Load file (this also stores the filename, extno and
             // extname)
-            if (gammalib::strip_whitespace(extno).length() > 0) {
-                load(filename, gammalib::toint(extno));
+            if (!gammalib::strip_whitespace(extno).empty()) {
+                load(filename+"["+extno+"]");
             }
-            else if (gammalib::strip_whitespace(extname).length() > 0) {
-                load(filename, extname);
+            else if (!gammalib::strip_whitespace(extname).empty()) {
+                load(filename+"["+extname+"]");
             }
             else {
                 load(filename);
@@ -442,79 +399,32 @@ void GMWLObservation::load(const std::string& filename)
     // Clear observation
     clear();
 
-    // Allocate spectrum
-    GMWLSpectrum* spec = new GMWLSpectrum;
-    m_events = spec;
-
-    // Load spectrum
-    spec->load(filename);
-
-    // Set attributes
-    name("Multi-wavelength observation");
-    id(filename);
-    m_filename   = filename;
-    m_instrument = spec->instrument();
-
-    // Return
-    return;
-}
-
-
-/***********************************************************************//**
- * @brief Load observation
- *
- * @param[in] filename File name.
- * @param[in] extno FITS extension number.
- ***************************************************************************/
-void GMWLObservation::load(const std::string& filename,
-                           const int&         extno)
-{
-    // Clear observation
-    clear();
-
-    // Allocate spectrum
-    GMWLSpectrum* spec = new GMWLSpectrum;
-    m_events = spec;
-
-    // Load spectrum
-    spec->load(filename, extno);
-
-    // Set attributes
-    name("Multi-wavelength observation");
-    id(filename+"["+gammalib::str(extno)+"]");
-    m_filename   = filename;
-    m_extno      = gammalib::str(extno);
-    m_instrument = spec->instrument();
-
-    // Return
-    return;
-}
-
-
-/***********************************************************************//**
- * @brief Load observation
- *
- * @param[in] filename File name.
- * @param[in] extname FITS extension name.
- ***************************************************************************/
-void GMWLObservation::load(const std::string& filename,
-                           const std::string& extname)
-{
-    // Clear observation
-    clear();
+    // Create file name
+    GFilename fname(filename);
 
     // Allocate spectrum
     GMWLSpectrum* spec = new GMWLSpectrum;
     m_events = spec;
 
     // Load spectrum
-    spec->load(filename, extname);
+    if (fname.has_extno()) {
+        spec->load(filename);
+        m_extno = gammalib::str(fname.extno());
+        id(filename+"["+m_extno+"]");
+    }
+    else if (fname.has_extname()) {
+        spec->load(filename);
+        m_extname = fname.extname();
+        id(filename+"["+m_extname+"]");
+    }
+    else {
+        spec->load(filename);
+        id(filename);
+    }
 
     // Set attributes
     name("Multi-wavelength observation");
-    id(filename+"["+extname+"]");
-    m_filename   = filename;
-    m_extname    = extname;
+    m_filename   = fname.filename();
     m_instrument = spec->instrument();
 
     // Return
diff --git a/inst/mwl/src/GMWLSpectrum.cpp b/inst/mwl/src/GMWLSpectrum.cpp
index c5f92c6..31f3abf 100644
--- a/inst/mwl/src/GMWLSpectrum.cpp
+++ b/inst/mwl/src/GMWLSpectrum.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *             GMWLSpectrum.cpp - Multi-wavelength spectrum class          *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2010-2013 by Juergen Knoedlseder                         *
+ *  copyright (C) 2010-2015 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -29,6 +29,7 @@
 #include <config.h>
 #endif
 #include "GTools.hpp"
+#include "GFilename.hpp"
 #include "GFits.hpp"
 #include "GFitsTable.hpp"
 #include "GEnergy.hpp"
@@ -259,70 +260,25 @@ GMWLSpectrum* GMWLSpectrum::clone(void) const
  ***************************************************************************/
 void GMWLSpectrum::load(const std::string& filename)
 {
-    // Clear object
-    clear();
-
-    // Open FITS file
-    GFits file(filename);
-
-    // Read spectrum
-    read(file);
-
-    // Close FITS file
-    file.close();
-
-    // Return
-    return;
-}
-
-
-/***********************************************************************//**
- * @brief Load spectrum from FITS file
- *
- * @param[in] filename FITS file name.
- * @param[in] extname FITS extension name.
- *
- * This method loads a spectrum from the specified extension from a FITS
- * file.
- ***************************************************************************/
-void GMWLSpectrum::load(const std::string& filename, const std::string& extname)
-{
-    // Clear object
-    clear();
-
-    // Open FITS file
-    GFits file(filename);
-
-    // Read spectrum from FITS file
-    read(file, extname);
-
-    // Close FITS file
-    file.close();
-
-    // Return
-    return;
-}
+    // Create file name
+    GFilename fname(filename);
 
-
-/***********************************************************************//**
- * @brief Load spectrum from FITS file
- *
- * @param[in] filename FITS file name.
- * @param[in] extno FITS extension number.
- *
- * This method loads a spectrum from the specified extension number from a
- * FITS file.
- ***************************************************************************/
-void GMWLSpectrum::load(const std::string& filename, const int& extno)
-{
     // Clear object
     clear();
 
     // Open FITS file
-    GFits file(filename);
+    GFits file(fname.filename());
 
-    // Read spectrum from FITS file
-    read(file, extno);
+    // Read spectrum
+    if (fname.has_extno()) {
+        read(file, fname.extno());
+    }
+    else if (fname.has_extname()) {
+        read(file, fname.extname());
+    }
+    else {
+        read(file);
+    }
 
     // Close FITS file
     file.close();
@@ -336,7 +292,7 @@ void GMWLSpectrum::load(const std::string& filename, const int& extno)
  * @brief Save spectrum
  *
  * @param[in] filename File name.
- * @param[in] clobber Overwrite existing file (default=false).
+ * @param[in] clobber Overwrite existing file (default: false).
  *
  * @todo To be implemented.
  ***************************************************************************/
diff --git a/inst/mwl/test/test_MWL.cpp b/inst/mwl/test/test_MWL.cpp
index 8235e2f..437f1b2 100644
--- a/inst/mwl/test/test_MWL.cpp
+++ b/inst/mwl/test/test_MWL.cpp
@@ -191,9 +191,9 @@ void TestGMWL::test_optimizer(void)
     test_try("Load multi-wavelength observations");
     try {
         obs.clear();
-        GMWLObservation comptel(crab_fits, "COMPTEL");
-        GMWLObservation lat(crab_fits, "LAT");
-        GMWLObservation hess(crab_fits, "HESS");
+        GMWLObservation comptel(crab_fits+"[COMPTEL]");
+        GMWLObservation lat(crab_fits+"[LAT]");
+        GMWLObservation hess(crab_fits+"[HESS]");
         obs.append(comptel);
         obs.append(lat);
         obs.append(hess);
diff --git a/pyext/GEbounds.i b/pyext/GEbounds.i
index aeef309..0625a84 100644
--- a/pyext/GEbounds.i
+++ b/pyext/GEbounds.i
@@ -39,12 +39,12 @@ class GEbounds : public GContainer {
 public:
     // Constructors and destructors
     GEbounds(void);
-    GEbounds(const GEbounds& ebds);
+    explicit GEbounds(const std::string& filename);
     explicit GEbounds(const GXmlElement& xml);
+    GEbounds(const GEbounds& ebds);
     GEbounds(const GEnergy& emin, const GEnergy& emax);
     GEbounds(const int& num, const GEnergy& emin, const GEnergy& emax,
              const bool& log = true);
-    GEbounds(const std::string& filename);
     virtual ~GEbounds(void);
 
     // Methods
diff --git a/pyext/GEnergies.i b/pyext/GEnergies.i
index c51a1d2..44378a3 100644
--- a/pyext/GEnergies.i
+++ b/pyext/GEnergies.i
@@ -41,8 +41,7 @@ class GEnergies : public GContainer {
 public:
     // Constructors and destructors
     GEnergies(void);
-    GEnergies(const std::string& filename,
-              const std::string& extname = "ENERGIES");
+    explicit GEnergies(const std::string& filename);
     GEnergies(const GEnergies& energies);
     GEnergies(const int& num, const GEnergy& emin, const GEnergy& emax,
               const bool& log = true);
@@ -64,13 +63,12 @@ public:
                                         const GEnergy& emax);
     void        set_log(const int& num, const GEnergy& emin,
                                         const GEnergy& emax);
-    void        load(const std::string& filename,
-                     const std::string& extname = "ENERGIES");
+    void        load(const std::string& filename);
     void        save(const std::string& filename,
-                     const bool&        clobber = false,
-                     const std::string& extname = "ENERGIES") const;
+                     const bool&        clobber = false) const;
     void        read(const GFitsTable& table);
-    void        write(GFits& file, const std::string& extname = "ENERGIES") const;
+    void        write(GFits& file,
+                      const std::string& extname = "ENERGIES") const;
 };
 
 
diff --git a/pyext/GGti.i b/pyext/GGti.i
index 4421b3d..82fec3f 100644
--- a/pyext/GGti.i
+++ b/pyext/GGti.i
@@ -36,9 +36,11 @@
  * @brief Good Time Interval class
  ***************************************************************************/
 class GGti : public GBase {
+
 public:
     // Constructors and destructors
     GGti(void);
+    explicit GGti(const std::string& filename);
     GGti(const GGti& gti);
     GGti(const GTime& tstart, const GTime& tstop);
     explicit GGti(const GXmlElement& xml);
@@ -59,11 +61,9 @@ public:
     void                  remove(const int& index);
     void                  reserve(const int& num);
     void                  extend(const GGti& gti);
-    void                  load(const std::string& filename,
-                               const std::string& extname = "GTI");
+    void                  load(const std::string& filename);
     void                  save(const std::string& filename,
-                               const bool& clobber = false,
-                               const std::string& extname = "GTI") const;
+                               const bool& clobber = false) const;
     void                  read(const GFitsTable& table);
     void                  write(GFits& file,
                                 const std::string& extname = "GTI") const;
diff --git a/pyext/GNodeArray.i b/pyext/GNodeArray.i
index 9820a67..76285cb 100644
--- a/pyext/GNodeArray.i
+++ b/pyext/GNodeArray.i
@@ -39,12 +39,14 @@ namespace std {
  * @brief Node array class
  ***************************************************************************/
 class GNodeArray : public GContainer {
+
 public:
     // Constructors and destructors
     GNodeArray(void);
-    GNodeArray(const int& num, const double* array);
+    explicit GNodeArray(const std::string& filename);
     explicit GNodeArray(const GVector& vector);
     explicit GNodeArray(const std::vector<double>& vector);
+    GNodeArray(const int& num, const double* array);
     GNodeArray(const GNodeArray& array);
     virtual ~GNodeArray(void);
 
@@ -70,10 +72,9 @@ public:
     const int&    inx_right(void) const;
     const double& wgt_left(void) const;
     const double& wgt_right(void) const;
-    void          load(const std::string& filename,
-                       const std::string& extname = "NODES");
-    void          save(const std::string& filename, const bool& clobber = false,
-                       const std::string& extname = "NODES") const;
+    void          load(const std::string& filename);
+    void          save(const std::string& filename,
+                       const bool& clobber = false) const;
     void          read(const GFitsTable& table);
     void          write(GFits& file,
                         const std::string& extname = "NODES") const;
diff --git a/src/obs/GEbounds.cpp b/src/obs/GEbounds.cpp
index 71a6fda..4b6fa93 100644
--- a/src/obs/GEbounds.cpp
+++ b/src/obs/GEbounds.cpp
@@ -77,17 +77,19 @@ GEbounds::GEbounds(void)
 
 
 /***********************************************************************//**
- * @brief Copy constructor
+ * @brief FITS file constructor
  *
- * @param[in] ebds Energy boundaries.
+ * @param[in] filename FITS file name.
+ *
+ * Constructs energy boundaries from a FITS file.
  ***************************************************************************/
-GEbounds::GEbounds(const GEbounds& ebds)
+GEbounds::GEbounds(const std::string& filename)
 {
-    // Initialise class members for clean destruction
+    // Initialise members
     init_members();
 
-    // Copy members
-    copy_members(ebds);
+    // Load FITS file
+    load(filename);
 
     // Return
     return;
@@ -99,7 +101,7 @@ GEbounds::GEbounds(const GEbounds& ebds)
  *
  * @param[in] xml XML element.
  *
- * Constructs energy bounds from an XML element.
+ * Constructs energy boundaries from an XML element.
  ***************************************************************************/
 GEbounds::GEbounds(const GXmlElement& xml)
 {
@@ -115,12 +117,30 @@ GEbounds::GEbounds(const GXmlElement& xml)
 
 
 /***********************************************************************//**
+ * @brief Copy constructor
+ *
+ * @param[in] ebds Energy boundaries.
+ ***************************************************************************/
+GEbounds::GEbounds(const GEbounds& ebds)
+{
+    // Initialise class members for clean destruction
+    init_members();
+
+    // Copy members
+    copy_members(ebds);
+
+    // Return
+    return;
+}
+
+
+/***********************************************************************//**
  * @brief Single energy band constructor
  *
  * @param[in] emin Minimum energy of the interval.
  * @param[in] emax Maximum energy of the interval.
  *
- * Constructs energy bounds for one (emin, emax) energy band.
+ * Constructs energy boundaries for one (emin, emax) energy band.
  ***************************************************************************/
 GEbounds::GEbounds(const GEnergy& emin, const GEnergy& emax)
 {
@@ -167,24 +187,6 @@ GEbounds::GEbounds(const int& num, const GEnergy& emin, const GEnergy& emax,
 
 
 /***********************************************************************//**
- * @brief Load constructor
- *
- * @param[in] filename FITS filename.
- ***************************************************************************/
-GEbounds::GEbounds(const std::string& filename)
-{
-    // Initialise members
-    init_members();
-
-    // Load FITS file
-    load(filename);
-
-    // Return
-    return;
-}
-
-
-/***********************************************************************//**
  * @brief Destructor
  ***************************************************************************/
 GEbounds::~GEbounds(void)
@@ -570,6 +572,9 @@ void GEbounds::set_log(const int& num, const GEnergy& emin, const GEnergy& emax)
  * @param[in] filename FITS file name.
  *
  * Loads the energy boundaries from a FITS file.
+ *
+ * If no extension name is provided, the energy boundaries are loaded from
+ * the "EBOUNDS" extension.
  ***************************************************************************/
 void GEbounds::load(const std::string& filename)
 {
@@ -603,7 +608,10 @@ void GEbounds::load(const std::string& filename)
  * @param[in] clobber Overwrite any existing file  (default: false)?
  * @param[in] unit Energy units (default: "keV")
  *
- * Saves the energy boundaries into a FITS file.
+ * Saves energy boundaries into a FITS file.
+ *
+ * If no extension name is provided, the energy boundaries are saved into
+ * an "EBOUNDS" extension.
  ***************************************************************************/
 void GEbounds::save(const std::string& filename,
                     const bool&        clobber,
diff --git a/src/obs/GEnergies.cpp b/src/obs/GEnergies.cpp
index 1ce4ee9..bb29869 100644
--- a/src/obs/GEnergies.cpp
+++ b/src/obs/GEnergies.cpp
@@ -30,6 +30,7 @@
 #endif
 #include "GTools.hpp"
 #include "GException.hpp"
+#include "GFilename.hpp"
 #include "GEnergies.hpp"
 #include "GFits.hpp"
 #include "GFitsTable.hpp"
@@ -71,20 +72,19 @@ GEnergies::GEnergies(void)
 
 
 /***********************************************************************//**
- * @brief Load constructor
+ * @brief FITS file constructor
  *
- * @param[in] filename FITS filename.
- * @param[in] extname Energies extension name (defaults to "ENERGIES")
+ * @param[in] filename FITS file name.
  *
- * Constructs energy container by loading energies from FITS file.
+ * Constructs energy container from a FITS file.
  ***************************************************************************/
-GEnergies::GEnergies(const std::string& filename, const std::string& extname)
+GEnergies::GEnergies(const std::string& filename)
 {
     // Initialise members
     init_members();
 
     // Load energies
-    load(filename, extname);
+    load(filename);
 
     // Return
     return;
@@ -534,21 +534,26 @@ void GEnergies::set_log(const int&     num,
 /***********************************************************************//**
  * @brief Load energies from FITS file
  *
- * @param[in] filename FITS filename.
- * @param[in] extname Energies extension name (defaults to "ENERGIES")
+ * @param[in] filename FITS file name.
  *
  * Loads the energies from FITS file.
+ *
+ * If no extension name is provided, the energies are loaded from the
+ * "ENERGIES" extension.
  ***************************************************************************/
-void GEnergies::load(const std::string& filename, const std::string& extname)
+void GEnergies::load(const std::string& filename)
 {
+    // Create file name
+    GFilename fname(filename);
+
     // Allocate FITS file
     GFits file;
 
     // Open FITS file
-    file.open(filename);
+    file.open(fname.filename());
 
     // Get energies table
-    const GFitsTable& table = *file.table(extname);
+    const GFitsTable& table = *file.table(fname.extname("ENERGIES"));
 
     // Read energies from table
     read(table);
@@ -566,24 +571,25 @@ void GEnergies::load(const std::string& filename, const std::string& extname)
  *
  * @param[in] filename FITS filename.
  * @param[in] clobber Overwrite any existing energies extension?
- * @param[in] extname Energies extension name (defaults to "ENERGIES")
  *
- * Saves energies into extension @p extname of a FITS file. If the file does
- * not exist it is created. If the file exists the energies are appended as
- * extension. If another energies extension exists already it is overwritten
- * if @p clobber=true.
+ * Saves energies into a FITS file.
+ *
+ * If no extension name is provided, the energies are saved into an
+ * "ENERGIES" extension.
  ***************************************************************************/
-void GEnergies::save(const std::string& filename, const bool& clobber,
-                     const std::string& extname) const
+void GEnergies::save(const std::string& filename, const bool& clobber) const
 {
+    // Create file name
+    GFilename fname(filename);
+
     // Allocate FITS file
     GFits file;
 
     // Write energies to FITS file
-    write(file, extname);
+    write(file, fname.extname("ENERGIES"));
 
     // Save to file
-    file.saveto(filename, clobber);
+    file.saveto(fname.filename(), clobber);
 
     // Return
     return;
@@ -637,7 +643,7 @@ void GEnergies::read(const GFitsTable& table)
  * @brief Write energies into FITS object
  *
  * @param[in] file FITS file.
- * @param[in] extname Energy extension name (defaults to "ENERGIES")
+ * @param[in] extname Energy extension name (default: "ENERGIES")
  *
  * Writes energies into FITS object.
  ***************************************************************************/
diff --git a/src/obs/GGti.cpp b/src/obs/GGti.cpp
index 007c810..5b2b736 100644
--- a/src/obs/GGti.cpp
+++ b/src/obs/GGti.cpp
@@ -30,6 +30,7 @@
 #endif
 #include "GException.hpp"
 #include "GTools.hpp"
+#include "GFilename.hpp"
 #include "GGti.hpp"
 #include "GFits.hpp"
 #include "GFitsTable.hpp"
@@ -73,6 +74,26 @@ GGti::GGti(void)
 
 
 /***********************************************************************//**
+ * @brief FITS file constructor
+ *
+ * @param[in] filename FITS file name.
+ *
+ * Constructs Good Time Intervals from a FITS file.
+ ***************************************************************************/
+GGti::GGti(const std::string& filename)
+{
+    // Initialise members
+    init_members();
+
+    // Load FITS file
+    load(filename);
+
+    // Return
+    return;
+}
+
+
+/***********************************************************************//**
  * @brief Copy constructor
  *
  * @param[in] gti Good Time Intervals.
@@ -551,20 +572,25 @@ void GGti::extend(const GGti& gti)
  * @brief Load Good Time Intervals from FITS file
  *
  * @param[in] filename FITS filename.
- * @param[in] extname GTI extension name (defaults to "GTI")
  *
  * Loads the Good Time Intervals from FITS file.
+ *
+ * If no extension name is provided, the energy boundaries are loaded from
+ * the "GTI" extension.
  ***************************************************************************/
-void GGti::load(const std::string& filename, const std::string& extname)
+void GGti::load(const std::string& filename)
 {
+    // Create file name
+    GFilename fname(filename);
+
     // Allocate FITS file
     GFits file;
 
     // Open FITS file
-    file.open(filename);
+    file.open(fname.filename());
 
     // Get GTI table
-    const GFitsTable& table = *file.table(extname);
+    const GFitsTable& table = *file.table(fname.extname("GTI"));
 
     // Read GTI from table
     read(table);
@@ -582,24 +608,25 @@ void GGti::load(const std::string& filename, const std::string& extname)
  *
  * @param[in] filename FITS filename.
  * @param[in] clobber Overwrite any existing GTI extension?
- * @param[in] extname GTI extension name (defaults to "GTI")
  *
- * Saves Good Time Intervals into extension @p extname of a FITS file. If the
- * file does not exist it is created. If the file exists the GTI is appended
- * as extension. If another GTI exists already it is overwritten if
- * @p clobber=true.
+ * Saves Good Time Intervals into a FITS file.
+ *
+ * If no extension name is provided, the Good Time Intervals are saved into
+ * an "GTI" extension.
  ***************************************************************************/
-void GGti::save(const std::string& filename, const bool& clobber,
-                const std::string& extname) const
+void GGti::save(const std::string& filename, const bool& clobber) const
 {
+    // Create file name
+    GFilename fname(filename);
+
     // Allocate FITS file
     GFits file;
 
     // Write GTI to FITS file
-    write(file, extname);
+    write(file, fname.extname("GTI"));
 
     // Save to file
-    file.saveto(filename, clobber);
+    file.saveto(fname.filename(), clobber);
 
     // Return
     return;
diff --git a/src/support/GNodeArray.cpp b/src/support/GNodeArray.cpp
index 0502520..9d98efd 100644
--- a/src/support/GNodeArray.cpp
+++ b/src/support/GNodeArray.cpp
@@ -1,7 +1,7 @@
 /***************************************************************************
  *                  GNodeArray.cpp - Array of nodes class                  *
  * ----------------------------------------------------------------------- *
- *  copyright (C) 2008-2014 by Juergen Knoedlseder                         *
+ *  copyright (C) 2008-2015 by Juergen Knoedlseder                         *
  * ----------------------------------------------------------------------- *
  *                                                                         *
  *  This program is free software: you can redistribute it and/or modify   *
@@ -29,9 +29,10 @@
 #include <config.h>
 #endif
 #include <cmath>
+#include "GTools.hpp"
 #include "GException.hpp"
+#include "GFilename.hpp"
 #include "GNodeArray.hpp"
-#include "GTools.hpp"
 #include "GFits.hpp"
 #include "GFitsTable.hpp"
 #include "GFitsBinTable.hpp"
@@ -75,6 +76,26 @@ GNodeArray::GNodeArray(void)
 
 
 /***********************************************************************//**
+ * @brief FITS file constructor
+ *
+ * @param[in] filename FITS file name.
+ *
+ * Constructs node array from a FITS file.
+ ***************************************************************************/
+GNodeArray::GNodeArray(const std::string& filename)
+{
+    // Initialise members
+    init_members();
+
+    // Load FITS file
+    load(filename);
+
+    // Return
+    return;
+}
+
+
+/***********************************************************************//**
  * @brief Element constructor
  *
  * @param[in] num Number of elements.
@@ -673,20 +694,25 @@ void GNodeArray::set_value(const double& value) const
  * @brief Load nodes from FITS file
  *
  * @param[in] filename FITS filename.
- * @param[in] extname Energies extension name (defaults to "NODES")
  *
- * Loads the nodes from FITS file.
+ * Loads the node array from a FITS file.
+ *
+ * If no extension name is provided, the node array is loaded from the
+ * "NODES" extension.
  ***************************************************************************/
-void GNodeArray::load(const std::string& filename, const std::string& extname)
+void GNodeArray::load(const std::string& filename)
 {
+    // Create file name
+    GFilename fname(filename);
+
     // Allocate FITS file
     GFits file;
 
     // Open FITS file
-    file.open(filename);
+    file.open(fname.filename());
 
     // Get nodes table
-    const GFitsTable& table = *file.table(extname);
+    const GFitsTable& table = *file.table(fname.extname("NODES"));
 
     // Read nodes from table
     read(table);
@@ -704,24 +730,25 @@ void GNodeArray::load(const std::string& filename, const std::string& extname)
  *
  * @param[in] filename FITS filename.
  * @param[in] clobber Overwrite any existing nodes extension?
- * @param[in] extname Nodes extension name (defaults to "NODES")
  *
- * Saves nodes into extension @p extname of a FITS file. If the file does
- * not exist it is created. If the file exists the nodes are appended as
- * extension. If another nodes extension exists already it is overwritten
- * if @p clobber=true.
+ * Saves node array into a FITS file.
+ *
+ * If no extension name is provided, the node array is saved into a
+ * "NODES" extension.
  ***************************************************************************/
-void GNodeArray::save(const std::string& filename, const bool& clobber,
-                      const std::string& extname) const
+void GNodeArray::save(const std::string& filename, const bool& clobber) const
 {
+    // Create file name
+    GFilename fname(filename);
+
     // Allocate FITS file
     GFits file;
 
     // Write nodes to FITS file
-    write(file, extname);
+    write(file, fname.extname("NODES"));
 
     // Save to file
-    file.saveto(filename, clobber);
+    file.saveto(fname.filename(), clobber);
 
     // Return
     return;
@@ -733,7 +760,7 @@ void GNodeArray::save(const std::string& filename, const bool& clobber,
  *
  * @param[in] table FITS table.
  *
- * Reads the nodes from a FITS table.
+ * Reads the nodes from a FITS @p table.
  ***************************************************************************/
 void GNodeArray::read(const GFitsTable& table)
 {