Before you use the microscope
Everyone who uses the lab's Evident CX43 phase-contrast microscope must complete this short course once. It consists of three videos (about 25 minutes in total) from the Microcourses series by Dr. Jennifer Waters, Director of the Nikon Imaging Center at Harvard Medical School, followed by a seven-question quiz. The videos cover the two ways objective lenses are most often ruined in shared facilities, immersion-oil misuse and physical contact, and the optical reason oil immersion matters at all.
To pass you must answer all seven questions correctly (a 90% threshold on seven questions rounds up to 7/7). Questions are drawn at random from a larger bank, so you can retake the quiz as many times as you need. When you pass, your completion is recorded automatically and Dr. Cheng Li is notified; you can then tick "I have been trained" on the usage log.
Course modules
Preventing Objective Lens Damage: Immersion Oil Problems 7:51
Watch for
- How the colour bands on an objective tell you whether it is a dry lens or an immersion lens, and which immersion medium it expects.
- Why too much oil is worse than too little: where excess oil goes inside the objective and what it does to the spring-mounted inner barrel.
- The dropper technique for applying oil, what to do (and not do) when you change samples, and how to remove oil at the end of a session.
- What oil under the top lens looks like, why it happens, and what accelerates it.
Preventing Objective Lens Damage: Blunt Force Trauma 12:26
Watch for
- Which part of the objective is most often damaged, and what a repair costs in money and time.
- The five ways a lens gets hit during routine use: the stage ledge, rotating the nosepiece, breaking a coverslip while focusing, tall custom chambers on inverted stands, and the edge of a neighbouring coverslip.
- The one focusing habit that prevents most of these: in which direction you are allowed to move the objective while looking through the eyepieces.
- What to do before you rotate the nosepiece and before you move between two coverslips on one slide.
Numerical Aperture 4:31
Watch for
- The definition NA = n sin θ, what n and θ stand for, and where NA is printed on the objective.
- Why a dry lens cannot exceed NA 1, and how immersion oil (with a refractive index matching coverslip glass) gets past that limit.
- How NA sets both resolution and image brightness, and what a lower-NA lens costs you in a live-cell experiment.
Microtutor: a virtual light-microscopy course 3:32
The playlist also includes a short introduction to Microtutor, a free online light-microscopy course from the same group. It is not covered by the quiz, but it is a good next step if you will be imaging regularly. The full playlists are here: Objective Lenses and Preventing Microscope Damage.