Raypaths and Ray History
For stray light analysis, it is quite common to use the Advanced Raytrace dialog with the "Create/use ray history file" and "Determine raypaths" options selected. Here is a brief explanation of these two options.
Selecting this option tells FRED to store all raypath information. This allows the user to then use diagnostic tools such as the Raytrace Paths and Stray Light Reports (found in Tools -> Reports) , the Image Artifact Diagnostic Tool, and the use of Ray Selection Filters in the Analysis Surface.
Create/user ray history file
This option saves coordinate data for every intersection point of every ray and is required if you wish to redraw the ray trajectories for a chosen path. Typically this is done from one of the Reports, via the right-click menu.