Celestron Advanced Biological Microscope 500 Microscope Basics - Page 16

Binocular Head Trinocular - this is a microscope with a binocular head for viewing and an additional port that can be used for a third eyepiece for a second person (or teacher) to use or it would be used for various photo applications. On many microscopes, the amount of light can be adjusted (from 30% to 70% or so) for the third port. Binocular heads contain prisms carrying light rays from the objectives to the eyepieces. The two eyepieces must be lined up with the user's pupils for comfortable viewing and this process is called adjusting the interpupillary distance (IPD). The eyepieces will get further apart or closer together to fit each individual as different people have varying distances between their eyes. Nosepiece (Turret or Revolving Nosepiece) The nosepiece is a rotating turret located above the stage on compound microscopes that can hold multiple objective lenses of various magnifications. By rotating the objectives into the light path and over the specimen you can observe various magnifications of the specimen during your examination. As any of the objectives are rotated they will click when the precise location is reached. There are normally three or four objectives (4x, 10x, 40x, and 100x) and in rare cases there are five. The objective can be of different powers but the ones just mentioned are used in the vast majority of all compound microscopes. Sometimes the 40x and 100x objectives are spring loaded at the end which allows the objective to be retracted slightly when nearing the slide/cover slip that may be too thick and this then prevents damage to the objective. Some nosepieces may be called "reverse nosepieces" and this is when the objectives are in a tucked position under the head and nosepiece allowing ease of placing slide specimens onto the stage from the front of the microscope. In a stereo microscope, a nosepiece can be referred to as a single objective housing or a turret that may have two objectives. If a turret type, the turret is rotated all the way in either direction to use the particular objective. Arm The arm (also called the stand or limb) is the component of a microscope which contains the focus mechanism and supports the stage, as well as the body or head which contains the eyepieces. It provides the rigidity of a microscope as it rises from the base. When moving a microscope, this is the part you should grab with one hand while putting your other hand under the base which will give you good protection. A few types of arms are: Fixed - a type of arm where the arm and the body are integral parts of the microscope and connected solidly to the base. Pillar (Post) - a type of arm which consists of a single post rising vertically from the base. The microscope body can rotate about the post and also be moved up and down on it. Boom (Universal) - a long boom type stand used to support a microscope body. It has many adjustments allowing the microscope to be aligned in a wide variety of configurations. This is the least common type of arm. Base The base is the bottom support part of the microscope. It provides balance and rigidity. It houses electrical components for illumination. Eyepiece Tubes The eyepiece tubes are also called observation tubes or drawtubes. They are attached to the arm above the nosepiece. They are usually set at angles of 45° or 30° for comfortable viewing. The bottom of the eyepiece tubes hold a special lens called 16