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PostPosted: Fri Jan 11, 2019 4:28 am 
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Location: Castlegar
No Immersion Oil
Image

With Immersion Oil
Image

A bit more detail around the mouth of the nematode with oil. When using oil the background shadow disappears.

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PostPosted: Fri Jan 11, 2019 5:26 am 
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An interesting comparison. It's good to know that the time spent slathering the objective in oil is well worth it. 8-)


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PostPosted: Mon Jan 14, 2019 12:14 am 
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The N.A. of your unoiled system is < 1.0 and is primarily dependent on the N.A. of the condenser, when the objective is used dry. Since you did not mention whether your condenser was oiled as well, nor the N.A. marked on the lens housing of your condenser, I am assuming that the condenser is consistent with what your microscope would have been fitted with at the factory, a 1.25 abbe type. Using that condenser dry, would limit it's N.A. to somewhere around .90 or below.

Your objective, being optically configured to be used with oil, is not just having it's N.A. limited, it is being used under a condition that induces spherical aberration as well. Objectives exist that are to be used dry, at an N.A. of between .90 and .95. In this case, a dry .90 condenser is also perfectly acceptable. This combination of optics , used dry, will produce an image far superior to the image your oil immersion objective used dry at roughly the same N.A. can produce, due to it being affected by spherical aberration.


When using an oil immersion objective, of greater than 1.0 N.A. , it is preferable to oil the condenser to the bottom of the slide as well, as long as the condenser is an oil type; and most of an N.A. over 1.0 are , unless otherwise marked.


If the condenser is used dry, the objective can still work at 1.25 N.A. if oiled but the condenser will place a limitation on the N.A. of light that is available to it. This does not limit the N.A. of the objective to the N.A. of the condenser but yields an N.A. that is part way between the two, somewhere around 1.10 , depending on the working N.A. of the condenser.


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PostPosted: Mon Jan 14, 2019 2:22 pm 
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Location: Castlegar
apochronaut, I am a newbee and do not know what N.A. is. Is there are more through paper or tutorial that you can point me too that discusses condensers, oil and N.A. ?
I would like to get the best images as possible using an oil objective.

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1) OMAX 40X-2500X 18MP USB3 Plan Phase Contrast Trinocular LED with Turret Phase Disk
2) AmScope Trinocular Stereo, 3.5X-90X Magnification Four-Zone LED Ring Light


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PostPosted: Mon Jan 14, 2019 3:28 pm 
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try this https://www.microscopyu.com/microscopy- ... l-aperture . Pay particular attention to the the first sentence of the paragraph, immediately following the first diagram in the article.


or this

http://microscopy.berkeley.edu/courses/ ... cs/na.html

this second article introduces the Rayleigh criteria, which shows how the resolution of an oil immersion objective under oiled conditions used with an oil immersion condenser under un-oiled conditions will be greater than the resolution of an oil immersion objective under un-oiled conditions used with an oil condenser under un-oiled conditions. In other words, the condenser does not limit the resolution of the the objective down to the condenser's working level.

The resultant resolution of an optical system in any case, is also determined by the internal design of the objective. In other words, the objective N.A. is not the only final arbiter of resolution. In some cases, the lack of adherence to an objective's immersion requirements results in a great loss of resolution and in others, such a lack of adherence results in only a minor loss of resolution.


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