What should be paid attention to when using oil lens for observation?
Before using the oil mirror, it is necessary to observe through low and high magnification mirrors, and then move the part that needs to be further magnified to the center of the field of view.
Raise the collector to its highest position and open the aperture to its maximum.
Rotate the converter to remove the high-power lens from the light hole, add a drop of tar onto the glass slide to be observed, and then slowly rotate the oil mirror. When converting the oil mirror, horizontally observe the distance between the lens and the glass slide from the side, so that the lens is immersed in the oil without crushing the glass slide.
Observe the eyepiece with your left eye and slowly rotate the fine adjuster until the image is clear.
If there is no object or the target is not ideal, when searching outside the refueling area, follow the procedure of low magnification → high magnification → fuel mirror. When searching in the refueling area, follow the procedure of low magnification → oil mirror, and do not use a high magnification mirror to avoid oil contaminating the lens.
After using the oil lens, first wipe it with lens cleaning paper, then use a small amount of xylene dipped lens cleaning paper to remove the cedarwood oil on the lens and specimen, and finally use dry lens cleaning paper to wipe it clean.
Why do we need to add a drop of tar when using an oil mirror
Due to the high magnification of the oil mirror and the small size of the lens, when light passes through medium objects of different densities (glass slide → air → lens), some of the light will refract and dissipate, resulting in less light entering the barrel and a darker field of view, making it difficult to observe objects clearly.
If cedarwood oil (n=1.515) with a refractive index similar to that of glass (n=1.52) is dropped between the lens and the glass slide, it will increase the amount of light entering the oil mirror, enhance the brightness of the field of view, and make the object image clear.
