Case 580K - determine Hydraulic oil level....

Hi there - I have a 1990 Case580k and the hydraulic oil level glass viewer is opaque and I can't really tell if the hydraulic oil is above that level where the glass sits or below it. Is there another way of telling (like a dipstick) what level I'm at....need to know if I need to add more or have added too much???

Thanks
Ron

Case 580K - determine Hydraulic oil level....