function [RMS] = LWBRMSalpha(filename,maxiter,alphasteps)

   load(filename,'-mat');                %image loaded as obj
   [npixels nangles] = size(obj);
   data = project2D(obj,nangles);
   
   alphamax = powermethod_LW(npixels,nangles);   %uses obj to estimate relaxation parameter
   step = alphamax/10;
   
   iold = backproject2D(data);     
   alpha = 0;
   
   for steps = 1:alphasteps
       alpha = alpha + step;
       fprintf('alpha value [%g] \n',steps)
       
       for i = 1:maxiter
    
            %fprintf('Landweber iteration [%g] \n',i);
            ptemp = project2D(iold,nangles);
            diff = data - ptemp;
            itemp = alpha.*backproject2D(diff);
            inew = iold + itemp;
            iold = inew;
            
       end
       predata = project2D(inew,nangles);
       dif = data - predata;
       RMS(steps) = norm(dif,2)/sqrt(npixels*nangles); 
   
   end
   
   index = 1:1:alphasteps;
   f1 = figure('Visible','on','Position',[300,200,600,800]);
   plot(index,RMS,'-b','Linewidth',2)
   
   
   