Spencer Lens Co Dedicated Darkfield Microscope Serial No 151187 Rhodium Plated

  

Here we have a beautiful Spencer Lens Company dedicated darkfield microscope. Because the condenser is of the darkfield type, and permanently mounted and aligned. The objective lens can be used for either darkfield or brightfield microscopy, however in darkfield mode (as in use on this microscope) the iris diaphragm of the objective is closed down somewhat to establish compatibility with the darkfield condenser.

The serial number of this microscope, 151187, places its date of manufacture in the year 1938, or just at the start of WWII. These microscopes were used in laboratories and hospitals for the examination of blood smears and for the rapid identification of spirochetes (Treponema pallidum). Nowadays, a good darkfield microscope can be used for the examination of pond water organisms with often spectacular results.

Organisms become luminous against a dark background and the views can be striking. Darkfield illumination can be compared to the effect produced when a beam of sunlight illuminates particles of dust floating in the air. Some microorganisms are nearly invisible when using a normal brightfield microscope, but with a darkfield microscope they become luminous... Similar to the night sky with bright stars against a black sky. Let's have a closer examination of this instrument.

The eyepiece is a 10X Huygenian eyepiece. Coarse and fine focus knobs operate smoothly and are rhodium plated.

All bright parts of the microscope are rhodium plated note: they are NOT chromium plated. Rhodium is a rare coating worth more than gold and virtually guaranteeing permanent brightness without corrosion. The fine focus knob is calibrated such that each 2 divisions on the scale correspond to a movement of 5 microns.

The objective lens is a fine Bausch and Lomb iris diaphragm objective, 97X. Its numerical aperture may be varied from 1.25 to 0.50 by means of the knurled iris diaphragm ring. The iris operates smoothly and positively. Magnification power of the microscope is 970X. The mechanical stage is clean and works smoothly in both the X- and Y- directions. Slides are held firmly in place by the clamping mechanism. The condenser is of the darkfield type, permanently mounted on a hinged mount and permanently aligned. The condenser is equipped with a 6V bulb.

The bulb is brand new. A voltage transformer (not included) is required to power the bulb located in the bottom of the condenser housing, however nowadays the bulb can simply be removed and light can be supplied using an LED lamp or flashlight. The substage darkfield condenser is hinged at the back end.

For cleaning, the knurled screw at the front of the condenser is unscrewed which allows lowering of the condenser for easy cleaning. The substage condenser is permanently aligned with the optical path and with the objective lens. The only manipulation necessary is focusing the objective. A darkfield microscope requires the use of immersion oil. Other construction features of this microscope: a sturdy, heavy stand, rigid arm which is hinged, large stable base, large 45mm body tube.

As stated, all bright parts are rhodium plated. I will include, with the microscope, a copy (not the original) of the 4-Page Spencer Darkfield microscope brochure. You can see photos of the pages of this brochure in the last few photos of the listing. Please note: Do not order this microscope unless you are familiar with, or willing to learn, the techniques of darkfield microscopy.

Darkfield microscopy requires patience and the use of immersion oil; both the objective lens and the condenser are oiled to the slide and careful focusing of the objective is critical, both in order to view the specimen and to avoid damage to the microscope slide. I have tested this microscope and it provides excellent darkfield images. It is a beautiful instrument. I do not use "Artificial Intelligence" to write my descriptions.