diff --git a/ChangeLog b/ChangeLog
index bec8ba22..3ed3adb1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -24,6 +24,7 @@ FIXED bug reported in MUSR-183: missing background for 2nd histo in asymmetry fi
 FIXED Makefiles so that the NeXus support will not be built if it has not been enabled during the configure stage
 FIXED ASCII export from musrview in case of a Fourier-Power- or Fourier-Phase-difference plot
 FIXED bug in asymmetry fit with fixed background
+CHANGED in case first good bin (fgb) is not given, it is now fgb=t0+(10ns/time resolution) (MUSR-190) 
 CHANGED improved handling of 'old' ROOT LEM data files (2006 and earlier) for any2many (MUSR-178)
 CHANGED improved handling of WKM/ASCII in PRunDataHandler for any2many (MUSR-172)
 CHANGED the data-file-name handling (MUSR-195).
diff --git a/src/classes/PRunAsymmetry.cpp b/src/classes/PRunAsymmetry.cpp
index f3ccfc74..b5651c85 100644
--- a/src/classes/PRunAsymmetry.cpp
+++ b/src/classes/PRunAsymmetry.cpp
@@ -839,16 +839,18 @@ Bool_t PRunAsymmetry::PrepareFitData(PRawRunData* runData, UInt_t histoNo[2])
   Int_t start[2] = {fRunInfo->GetDataRange(0), fRunInfo->GetDataRange(2)};
   Int_t end[2]   = {fRunInfo->GetDataRange(1), fRunInfo->GetDataRange(3)};
   Double_t t0[2] = {fT0s[0], fT0s[1]};
+  Int_t offset = (Int_t)(10.0e-3/fTimeResolution); // needed in case first good bin is not given, default = 10ns
+
   // check if data range has been provided, and if not try to estimate them
   if (start[0] < 0) {
-    start[0] = (Int_t)t0[0]+5;
-    cerr << endl << ">> PRunAsymmetry::PrepareData(): **WARNING** data range (forward) was not provided, will try data range start = t0+5 = " << start[0] << ".";
+    start[0] = (Int_t)t0[0]+offset;
+    cerr << endl << ">> PRunAsymmetry::PrepareData(): **WARNING** data range (forward) was not provided, will try data range start = t0+" << offset << "(=10ns) = " << start[0] << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";
     cerr << endl;
   }
   if (start[1] < 0) {
-    start[1] = (Int_t)t0[1]+5;
-    cerr << endl << ">> PRunAsymmetry::PrepareData(): **WARNING** data range (backward) was not provided, will try data range start = t0+5 = " << start[1] << ".";
+    start[1] = (Int_t)t0[1]+offset;
+    cerr << endl << ">> PRunAsymmetry::PrepareData(): **WARNING** data range (backward) was not provided, will try data range start = t0+" << offset << "(=10ns) = " << start[1] << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";
     cerr << endl;
   }
@@ -1052,14 +1054,15 @@ Bool_t PRunAsymmetry::PrepareViewData(PRawRunData* runData, UInt_t histoNo[2])
   Int_t start[2] = {0, 0};
   Int_t end[2] = {0, 0};
   Double_t t0[2] = {fT0s[0], fT0s[1]};
+  Int_t offset = (Int_t)(10.0e-3/fTimeResolution); // needed in case first good bin is not given, default = 10ns
   // check if data range has been provided, and if not try to estimate them
   if (fRunInfo->GetDataRange(0) < 0) {
-    start[0] = (static_cast<Int_t>(t0[0])+5) - ((static_cast<Int_t>(t0[0])+5)/packing)*packing;
+    start[0] = (static_cast<Int_t>(t0[0])+offset) - ((static_cast<Int_t>(t0[0])+offset)/packing)*packing;
     cerr << endl << ">> PRunAsymmetry::PrepareViewData(): **WARNING** data range (forward) was not provided, will try data range start = " << start[0] << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";
     cerr << endl;
   } else if (fRunInfo->GetDataRange(2) < 0) {
-    start[1] = (static_cast<Int_t>(t0[1])+5) - ((static_cast<Int_t>(t0[1])+5)/packing)*packing;
+    start[1] = (static_cast<Int_t>(t0[1])+offset) - ((static_cast<Int_t>(t0[1])+offset)/packing)*packing;
     cerr << endl << ">> PRunAsymmetry::PrepareViewData(): **WARNING** data range (backward) was not provided, will try data range start = " << start[1] << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";
     cerr << endl;
@@ -1306,14 +1309,15 @@ Bool_t PRunAsymmetry::PrepareRRFViewData(PRawRunData* runData, UInt_t histoNo[2]
   Int_t end[2] = {0, 0};
   Double_t t0[2] = {fT0s[0], fT0s[1]};
   UInt_t packing = fMsrInfo->GetMsrPlotList()->at(0).fRRFPacking;
+  Int_t offset = (Int_t)(10.0e-3/fTimeResolution); // needed in case first good bin is not given, default = 10ns
   // check if data range has been provided, and if not try to estimate them
   if (fRunInfo->GetDataRange(0) < 0) {
-    start[0] = static_cast<Int_t>(t0[0])+5;
+    start[0] = static_cast<Int_t>(t0[0])+offset;
     cerr << endl << ">> PRunAsymmetry::PrepareRRFViewData(): **WARNING** data range (forward) was not provided, will try data range start = " << start[0] << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";
     cerr << endl;
   } else if (fRunInfo->GetDataRange(2) < 0) {
-    start[1] = static_cast<Int_t>(t0[1])+5;
+    start[1] = static_cast<Int_t>(t0[1])+offset;
     cerr << endl << ">> PRunAsymmetry::PrepareRRFViewData(): **WARNING** data range (backward) was not provided, will try data range start = " << start[1] << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";
     cerr << endl;
diff --git a/src/classes/PRunSingleHisto.cpp b/src/classes/PRunSingleHisto.cpp
index b41487a4..00939e79 100644
--- a/src/classes/PRunSingleHisto.cpp
+++ b/src/classes/PRunSingleHisto.cpp
@@ -719,8 +719,9 @@ Bool_t PRunSingleHisto::PrepareFitData(PRawRunData* runData, const UInt_t histoN
   end   = fRunInfo->GetDataRange(1);
   // check if data range has been provided, and if not try to estimate them
   if (start < 0) {
-    start = fT0s[0]+5;
-    cerr << endl << ">> PRunSingleHisto::PrepareData(): **WARNING** data range was not provided, will try data range start = t0+5 = " << start << ".";
+    Int_t offset = (Int_t)(10.0e-3/fTimeResolution);
+    start = fT0s[0]+offset;
+    cerr << endl << ">> PRunSingleHisto::PrepareData(): **WARNING** data range was not provided, will try data range start = t0+" << offset << "(=10ns) = " << start << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";
     cerr << endl;
   }
@@ -858,7 +859,8 @@ Bool_t PRunSingleHisto::PrepareRawViewData(PRawRunData* runData, const UInt_t hi
   Int_t end   = start + ((runData->GetDataBin(histoNo)->size()-start)/packing)*packing;
   // check if data range has been provided, and if not try to estimate them
   if (start < 0) {
-    start = (fT0s[0]+5) - ((fT0s[0]+5)/packing)*packing;
+    Int_t offset = (Int_t)(10.0e-3/fTimeResolution);
+    start = (fT0s[0]+offset) - ((fT0s[0]+offset)/packing)*packing;
     end = start + ((runData->GetDataBin(histoNo)->size()-start)/packing)*packing;
     cerr << endl << ">> PRunSingleHisto::PrepareData(): **WARNING** data range was not provided, will try data range start = " << start << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";
@@ -1057,7 +1059,8 @@ Bool_t PRunSingleHisto::PrepareViewData(PRawRunData* runData, const UInt_t histo
 
   // check if data range has been provided, and if not try to estimate them
   if (start < 0) {
-    start = (fT0s[0]+5) - ((fT0s[0]+5)/packing)*packing;
+    Int_t offset = (Int_t)(10.0e-3/fTimeResolution);
+    start = (fT0s[0]+offset) - ((fT0s[0]+offset)/packing)*packing;
     end = start + ((runData->GetDataBin(histoNo)->size()-start)/packing)*packing;
     cerr << endl << ">> PRunSingleHisto::PrepareData(): **WARNING** data range was not provided, will try data range start = " << start << ".";
     cerr << endl << ">> NO WARRANTY THAT THIS DOES MAKE ANY SENSE.";