Strange blur around reticle pointer

I do an 360degree App for Android and have a strange issue i have a little white blur around my reticle pointer and i have no clue how to fix that.!

pls help here the shader i used. Its from the GoogleVR-Asset.

 Shader "GoogleVR/Reticle" {
   Properties {
     _Color  ("Color", Color) = ( 1, 1, 1, 1 )
     _InnerDiameter ("InnerDiameter", Range(0, 10.0)) = 1.5
     _OuterDiameter ("OuterDiameter", Range(0.00872665, 10.0)) = 2.0
     _DistanceInMeters ("DistanceInMeters", Range(0.0, 100.0)) = 2.0
   }
 
   SubShader {
     Tags { "Queue"="Overlay" "IgnoreProjector"="True" "RenderType"="Transparent" }
     Pass {
       Blend SrcAlpha OneMinusSrcAlpha
       AlphaTest Off
       Cull Back
       Lighting Off
       ZWrite Off
       ZTest Always
 
       Fog { Mode Off }
       CGPROGRAM
 
       #pragma vertex vert
       #pragma fragment frag
 
       #include "UnityCG.cginc"
 
       uniform float4 _Color;
       uniform float _InnerDiameter;
       uniform float _OuterDiameter;
       uniform float _DistanceInMeters;
 
       struct vertexInput {
         float4 vertex : POSITION;
       };
 
       struct fragmentInput{
           float4 position : SV_POSITION;
       };
 
       fragmentInput vert(vertexInput i) {
         float scale = lerp(_OuterDiameter, _InnerDiameter, i.vertex.z);
 
         float3 vert_out = float3(i.vertex.x * scale, i.vertex.y * scale, _DistanceInMeters);
 
         fragmentInput o;
         o.position = UnityObjectToClipPos (vert_out);
         return o;
       }
 
       fixed4 frag(fragmentInput i) : SV_Target {
         fixed4 ret = _Color;
         return ret;
       }
 
       ENDCG
     }
   }
 }
 

the material is also the default one from the asset. I also figured out that when i have a bigger screen the blur is much less.

[1]: /storage/temp/112845-screenshot-02.jpg