diff --git a/docs/lightcurve.rst b/docs/lightcurve.rst
index 6f345173..805f5550 100755
--- a/docs/lightcurve.rst
+++ b/docs/lightcurve.rst
@@ -74,11 +74,14 @@ where the :math:`w_{\mathrm{col}, ij}` is the dimensionless column kernel.
 
 The spectra were then summed across the frequencies and pixels to produce the bolometric luminosity, listed in [02  Luminosity] in the outputted .out file.
 
+The bounds of the ray-traced region is by default equal to the extent of the particle positions in the dump file. Any number of these automatically calculated bounds can be overriden with the ``SPLASH_MARGIN_XMIN``, ``SPLASH_MARGIN_XMAX``, ``SPLASH_MARGIN_YMIN`` and ``SPLASH_MARGIN_YMAX`` environment variables or the ``--xmin``, ``--xmax``, ``--ymin`` and ``--ymax`` flags. The units of these bounds are the same as the units of the particle positions.
 
 When ``--temperature`` is set, temperature :math:`T` is computed at **read time** from density :math:`\rho` and
 specific internal energy :math:`u` using *get_temp_from_u()* in ``lightcurve_utils.f90``, assuming gas and
 radiation pressure in local thermodynamic equilibrium (see :ref:`sec:lckappa`).
 
+The temperature for each SPH particle can be altered with a scaling factor (called the spectral hardening factor) and constant offset. The scaling factor is set using the flag ``--fcol`` and the constant offset with the flag ``--ocol``. The scaling factor is applied first and the constant offset is added to the scaled temperature.
+
 Opacity :math:`\kappa` used in the ray trace is described in :ref:`sec:lckappa`.
 
 
diff --git a/src/lightcurve.f90 b/src/lightcurve.f90
index 472d1251..66a8f4a2 100644
--- a/src/lightcurve.f90
+++ b/src/lightcurve.f90
@@ -83,7 +83,7 @@ subroutine get_lightcurve(ncolumns,dat,npartoftype,masstype,itype,ndim,ntypes,&
  real, dimension(:),   allocatable :: freq,spectrum,bb_spectrum
  real, dimension(:,:), allocatable :: img,taupix,flux_nu,v_on_c,badpix
  real, dimension(:,:,:), allocatable :: img_nu,img_tmp
- real :: zobs,dzobs,dx,dy,area,freqmin,freqmax,lam_max,freq_max,bb_scale,opacity_factor,f_col
+ real :: zobs,dzobs,dx,dy,area,freqmin,freqmax,lam_max,freq_max,bb_scale,opacity_factor,f_col,o_col
  real :: betaz,lorentz,doppler_factor,doppler_factor_max,tempi,badarea
  real :: rstar,lstar
  logical :: relativistic,nofits
@@ -127,8 +127,27 @@ subroutine get_lightcurve(ncolumns,dat,npartoftype,masstype,itype,ndim,ntypes,&
  if (f_col < 0.0) f_col = renvironment('f_col', 1.0)
  print "(/,a,f5.2,/,a,/)",' SPECTRAL HARDENING FACTOR f_col = ',f_col, &
                           ' (use --fcol=1.7 for radiation-pressure dominated flows; Shimura & Takahara 1995)'
+ o_col = renvironment('ocol')
+ print "(a,f8.2)"," Temperature offset: ",o_col
+
+ !If the user does not provide a limit for the render region it is calculated automatically.
  xmin(1:ndim) = lim(ix(1:ndim),1)
- xmax(1:ndim) = lim(ix(1:ndim),2)
+ xmax(1:ndim) = lim(ix(1:ndim),2)      
+ xmin(1) = renvironment('SPLASH_MARGIN_XMIN', xmin(1))
+ xmax(1) = renvironment('SPLASH_MARGIN_XMAX', xmax(1))
+ xmin(2) = renvironment('SPLASH_MARGIN_YMIN', xmin(2))
+ xmax(2) = renvironment('SPLASH_MARGIN_YMAX', xmax(2))
+
+ if (xmax(1) <= xmin(1)) then
+    print *,"ERROR: maximum x axis render bound less than or equal to minimum x axis render region bound, aborting..."
+    ierr = 3
+    return
+ endif
+ if (xmax(2) <= xmin(2)) then
+    print *,"ERROR: maximum y axis render bound less than or equal to minimum y axis render region bound, aborting..."
+    ierr = 4
+    return
+ endif
  !
  !--set number of particles to use in the interpolation routines
  !  and allocate memory for weights
@@ -137,7 +156,7 @@ subroutine get_lightcurve(ncolumns,dat,npartoftype,masstype,itype,ndim,ntypes,&
  allocate(weight(n),x(n),y(n),z(n),flux(n),opacity(n),h(n),stat=ierr)
  if (ierr /= 0) then
     print*,' ERROR allocating memory for interpolation weights, aborting...'
-    ierr = 3
+    ierr = 5
     return
  endif
  x(1:n) = dat(1:n,ix(1))
@@ -213,8 +232,8 @@ subroutine get_lightcurve(ncolumns,dat,npartoftype,masstype,itype,ndim,ntypes,&
  opacity_factor = 1.
  doppler_factor_max = 0.
  !$omp parallel do default(none) &
- !$omp shared(n,nfreq,freq,flux,flux_nu,dat,h,weight,radkernel) &
- !$omp shared(opacity,relativistic,v_on_c,itemp,f_col) &
+ !$omp shared(n,nfreq,freq,flux,flux_nu,dat,h,weight,radkernel,ierr) &
+ !$omp shared(opacity,relativistic,v_on_c,itemp,f_col,o_col) &
  !$omp private(i,betaz,lorentz,tempi,rstar,lstar) &
  !$omp firstprivate(opacity_factor,doppler_factor) &
  !$omp reduction(max:doppler_factor_max)
@@ -239,12 +258,20 @@ subroutine get_lightcurve(ncolumns,dat,npartoftype,masstype,itype,ndim,ntypes,&
        lstar = 4.*pi*rstar**2*steboltz*tempi**4
        print "(a,2(es10.3,a),/)",' Luminosity of sink = ',lstar,' erg/s = ',lstar/Lsun,' L_sun'
     else
-       tempi = dat(i,itemp)*f_col
+       tempi = (dat(i,itemp)*f_col)+o_col
+       if (tempi <= 0.0) ierr = 6
+       
     endif
     !call get_opacity_nongrey(nfreq,freq,dat(i,temp),dat(i,rho),opacity_nu(:,i))
-    flux_nu(:,i) = B_nu(tempi,freq*doppler_factor)
+    if (ierr /= 6) flux_nu(:,i) = B_nu(tempi,freq*doppler_factor)
  enddo
  !$omp end parallel do
+
+ if (ierr == 6) then
+     print *,"ERROR: choice of temperature offset has resulted in a zero or negative temperature for at least one particle, aborting..."
+     return
+ endif
+ 
  if (relativistic) print*,' max relativistic correction=',doppler_factor_max
 
  if (allocated(img_nu)) deallocate(img_nu)