Popup positioning in wpf using c#

Question

I have placed a popup on a button mouseover.Each time when i mouse over that button my custom designed popup is being showed perfectly.Butit doesn't point the button perfectly. How to do so ..? Now my popup looks like

I want that arrow mark to point that help button How to acheive it..

Here is my code for the button and popup in xaml

<telerik:RadButton Name="btnH" Grid.Column="1" HorizontalAlignment="Left" Margin="444,56,0,0" Grid.Row="2" VerticalAlignment="Top" 
                 Width="23" Height="23" BorderThickness="6" BorderBrush="#4E4E4E">
            <Image Source="Images/help.png" />
            <telerik:RadButton.Triggers>
                    <EventTrigger RoutedEvent="MouseEnter">
                        <BeginStoryboard>
                        <Storyboard TargetName="TooltipPopup" TargetProperty="IsOpen">
                                <BooleanAnimationUsingKeyFrames  FillBehavior="HoldEnd">
                                    <DiscreteBooleanKeyFrame KeyTime="00:00:00"  Value="True" />
                                </BooleanAnimationUsingKeyFrames>
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger>

and below is the custom usercontrol xaml which amn calling in popup

<UserControl
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation" x:Class="WPFTest.UCToolTip" 
         mc:Ignorable="d" Height="231.493" Width="362.075"
         Background="Transparent"  >
<UserControl.Resources>
    <Style TargetType="{x:Type Hyperlink}">
                 <Setter Property="TextBlock.TextDecorations" Value="{x:Null}" />
    </Style>
</UserControl.Resources>
<Grid Margin="10,0,0,0">
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>
    <Grid Background="red" Margin="0,0,182,133">            

    </Grid>
    <Polygon
    Points="0.5,0 15,0, 0,30" Stroke="Orange" Fill="Orange" Margin="0,98,0,101" />
</Grid>

Answer 1

use this style for your Popup:

<Style TargetType="Popup">
                <Style.Triggers>
                    <Trigger Property="IsOpen" Value="true">
                        <Setter Property="PlacementTarget" Value="{Binding ElementName=btnH }" />
                        <Setter Property="Placement" Value="Top" />
                        <Setter Property="VerticalOffset" Value="-5" />
                        <Setter Property="HorizontalOffset" Value="5" />
                    </Trigger>
                </Style.Triggers>
            </Style>