For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the eyepiece with the plano (flat) side facing the eye.
If kidney function begins to decline, BUN and creatinine rise. A normal creatinine depends on muscle mass and age. In general, a normal creatine is 0.5 to 1.2 milligrams per deciliter (mg/dL). A normal BUN is 7 to 20 mg/dL.
Those three letters stand for blood, urea, and nitrogen. A BUN test measures the level or urea nitrogen present in your blood, and can contain important information about the status of your kidneys and liver. The BUN test is usually ordered if your doctor needs to evaluate your kidney function, or suspects kidney damage.