Phasecontrastmicroscopeimages

Since your telescope’s objective diameter and focal length are fixed, eyepieces are the one thing you can easily change in this equation. Note that shorter eyepieces give you higher magnification and narrower FOV.

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Phasecontrastmicroscopeppt

This page titled 3.3B: Phase-Contrast Microscopy is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Boundless via source content that was edited to the style and standards of the LibreTexts platform.

Focal ratios in common use by amateur astronomers range from f/4 to f/10. Wider and narrower telescopes exist, but are less common. Amateur astronomers tend to categorize ratios into wide, medium, and narrow views. Imagine wide angle views by touching your thumb to forefinger so you have a circle and place it around your eye. A narrow field of view would be looking through a paper towel roll or even a drinking straw.

PhasecontrastmicroscopePDF

Phase-contrast microscopy allows the visualization of living cells in their natural state with high contrast and high resolution. This tool works best with a thin specimen and is not ideal for a thick specimen. Phase-contrast images have a characteristic grey background with light and dark features found across the sample. One disadvantage of phase-contrast microscopy is halo formation called halo-light ring.

Phasecontrastmicroscopeparts

Note how Power Per Inch changes with decreasing eyepiece focal length. Judging if a scope and eyepiece combination would work in Earth’s soupy atmosphere is the primary function of PPI.

If you’re still not sure how this works, perhaps these charts will help explain how a telescope’s focal length, focal ratio, and magnification interact. Each chart keeps one of the three specifications the same while changing the others.

Phasecontrastmicroscopeapplication

In phase-contrast microscopy, parallel beams of light are passed through objects of different densities. The microscope contains special condensers that throw light “out of phase” causing it to pass through the object at different speeds. Internal details and organelles of live, unstained organisms (e.g. mitochondria, lysosomes, and the Golgi body) can be seen clearly with this microscope.

This is the reason why many amateur astronomers pay big bucks for high end eyepieces with a 60+ degree field of view, especially for telescopes with long focal lengths and high natural magnification. Since 2″ eyepieces are easier to design with a wider view, they are a popular option.

To know how your scope will perform and what objects it is best suited to view, you’ll need to know a few things. Start with your telescope’s focal length and objective diameter, plus the AFOV for each eyepiece.

Phasecontrastmicroscopeprinciple

Telescopes with longer focal lengths will have higher magnification and narrower field of view. Longer focal lengths are better suited to smaller objects while shorter ones are better for wide views.

Now let’s flip this on its ear and increase the scope’s focal length while keeping a 100mm objective and a 20mm Plossl eyepiece. Note how the Magnification and FOV change as the focal length gets longer:

Phasecontrastmicroscopediagram

Next let’s tinker with scope parameters and see how that changes our magnification and FOV. First up, let’s look at increasing diameter to a whopping 27″ telescope:

A phase ring in condenser allows a cylinder of light to pass through it while still in phase. Unaltered light hits the phase ring in the lens and is excluded. Light that is slightly altered by passing through a different refractive index is allowed to pass through. Light passing through cellular structures, such as chromosomes or mitochondria is retarded because they have a higher refractive index than the surrounding medium. Elements of lower refractive index advance the wave. Much of the background light is removed and light that constructively or destructively interfered is let through with enhanced contrast.

Phase-contrast microscopy visualizes differences in the refractive indexes of different parts of a specimen relative to unaltered light.

Phase-contrast microscopy is a method of manipulating light paths through the use of strategically placed rings in order to illuminate transparent objects. Dutch physicist Fritz Zernike developed the technique in the 1930s; for his efforts he was awarded the Nobel Prize in 1953.