Rotate image smoothy in Silverlight

<grid x:name="LayoutRootNew" grid.row="0" grid.columnspan="3" grid.rowspan="3" margin="11,40,0,0" verticalalignment="Top" xmlns:x="#unknown">
              
                
                <grid.projection>
                    <planeprojection rotationx="-51" />
                </grid.projection>
                

                <Image  Name="imgArrow1" Source="@../../Images/circle31mar.png" Stretch="Uniform" UseLayoutRounding="True"  Height="340" Width="340" HorizontalAlignment="Center" VerticalAlignment="Center">
                    <Image.Projection>
                        <planeprojection x:name="Image1Projection" centerofrotationx="0.5" centerofrotationy="0.5" />
                    </Image.Projection>
                    <Image.RenderTransform>
                        <rotatetransform x:name="Prize_ListWheel_Rotate">
                                     Angle="0" />
                    </Image.RenderTransform>
                 
                </Image>
                <Image Name="imgArrow2" Source="@../../Images/FRRingNew3.png" Margin="0,0,0,0" Height="222" Width="225" HorizontalAlignment="Center">
                    <Image.Projection>
                        <planeprojection x:name="Image1Projection2" centerofrotationx="0.5" centerofrotationy="0.5" />
                    </Image.Projection>
                </Image>

            </rotatetransform></grid>

_n = gameDataBO.FRRndNumber;         //Animation for red black Wheel
SessionManager.newrandom = _n;
             
// _n = SessionManager.rnno;

//-----new work start---------
randomnumber = _n;
animanglerot = 360.0 / Convert.ToDouble(itextmaxcount);
anglesteps = Convert.ToInt64((itextmaxcount * 2 * numberofrotations - 38) * anglefactor);

//----------new work end---------

imgArrow1.RenderTransformOrigin = new Point(0.5, 0.5);
imgArrow1.RenderTransform = new RotateTransform();

da = new DoubleAnimation();

da.From = 0;
da.To = -anglesteps;  //-360.00 * 1.9;// -(360.00 / 38.00);
anglesteps = anglesteps - 1;
Prize_ListWheel_Rotate.Angle += animanglerot / anglefactor;
//myDispatcherTimer.Interval = new TimeSpan(0, 0, 0, 0, 300); // 100 Milliseconds 
//myDispatcherTimer.Start();
da.Duration = TimeSpan.FromSeconds(2);

SineEase be = new SineEase();

be.EasingMode = EasingMode.EaseIn;
// da.EasingFunction = be;

_nRing = gameDataBO.FRRingRndNumber;     //Animation for Ring
SessionManager.newringrandom = _nRing;
_nRing = SessionManager.ringno;
imgArrow2.RenderTransformOrigin = new Point(0.5, 0.5);

imgArrow2.RenderTransform = new RotateTransform();
da2 = new DoubleAnimation();
da2.From = 0;
da2.To = 360.00 * 1;// +(360.00 / 38.00);
da2.Duration = TimeSpan.FromSeconds(2);
// da2.EasingFunction = be;

_netRotation = (_n + _nRing);

if (_netRotation > 38)
{
   _netRotation = (_netRotation % 38);
}

_finalAngle = _netRotation * (360.00 / 38.00);

Storyboard.SetTarget(da, imgArrow1.RenderTransform);
Storyboard.SetTarget(da2, imgArrow2.RenderTransform);
Storyboard.SetTargetProperty(da, new PropertyPath(RotateTransform.AngleProperty));
Storyboard.SetTargetProperty(da2, new PropertyPath(RotateTransform.AngleProperty));

sb1 = new Storyboard();
sb1.Children.Add(da);
sb1.Children.Add(da2);
sb1.Begin();
SessionManager.newsession = 0;