Starry Night Pro provides the angular separation and the angle "subtended" to the observer.
The following image shows the Moon. If you look in the INFO pane ---> Position in Space ---> Heliocentric Y axis ---> 0.54. This is the angle "subtended" at the observer.
In the top-left corner, there is a drop down menu that allows you to choose between different tools, and one of them is Angular Separation. After selecting this, click and hold on any object, then drag the mouse cursor to another object. The red line shows the Angular Separation. You can also use the Angular Separation tool to measure from the object to the viewer. Click on the object and drag down.