farnsy wrote: ↑Mon Jul 12, 2021 6:18 pm
Not yet, but I will, more frequently I'll use a drop of water on there.
I think I need to make a 3D printed part that holds this rigidly to replace this dovetail kludge. Having lateral play is a bit of a pain as the condenser often moves when I am adjusting it's diaphragm. I can use it right now, but the project is not done.
It will also move due to drag from the immersion medium.
Without oil , your condenser functions somewhere between .90 and .95 N.A., certainly enough to keep the objectives you are using happy. However, in trialling various 1.4 N.A. condensers both oiled and dry, their performance seems to suffer more from not being oiled than an abbe aspheric 1.25. The oil space between the slide and the condenser is integral to it's achromatism ; it needs an n homogeneity of the successive layers in the medium stack between the condenser and object . Leaving air in between the condenser and the bottom of the slide not only reduces the N.A. but it also introduces some ca into the illumination beam, somewhat negating the benefit of having an achromat condenser. Dedicated .90 dry condensers factor in the air space and in the case of a .90 achromat, will outperform other condensers built to a homogeneous tolerance, whether achromat or not and whether they are high N.A. or not.
Certainly, if you eventually spring for the 1.30 plan fluor or the 1.45 planapo, having a 1.4 achromat will be highly beneficial but only if you oil it.
To illustrate the negative effects of not oiling a high N.A. oil condenser one can use the Rayleigh Criteria to calculate the theoretical resolution of your 1.10 water immersion objective with mid wavelength green light. I am assuming that unoiled condensers work at .90 N.A. but some might work a little higher.
1.22 X 500 ÷ (.90 + 1.10) = .305 microns . Oil the condenser and it is . 1.22 X 500 ÷( 1.10 + 1.10 ) = .277 microns. .
In comparison the difference with the 1.30 plan fluor objective and an unoiled condenser is thus.
1.22 X 500 ÷ (.90+1.30) = 2.77 microns, or the same as the water immersion using an oiled condenser however, the 1.30 plan fluor suffers much less from the detail masking due to the refraction typical of achromats. Oiled , the 1.30 yields 1.22 X 500 ÷ ( 1.30 + 1.30) = .235 microns.
The importance of oiling the condenser is further illustrated by the fact that a typical and standard system such as a 1.25 abbe condenser used with a 1.25 oil immersion abbe condenser will achieve 1.22 X 500 ÷ (1.25 +1.25) = .244 microns theoretically , whereas the same condenser unoiled or a .90 achromat used with a 1.4 N.A. objective will achieve only 1.22 X 500 ÷ ( .90 + 1.40) = .265 microns. theoretically. Less than a ubiquitous 1.25 achromat. It doesn't make any sense to splurge for an expensive plan fluor or planapo objective and not use an oil immersion condenser.
Replacing oil with water probably does not make sense either. In tests that I did with 5 different condensers to fit the AO/Reichert Diastar, I trialled them all dry, with water and with Cargille type A immersion oil. The 5 condensers were # 1202 .90 achromat aplanat dry, # 1970 1.25 abbe aspheric oil immersion, # 1973 1.40 achromat aplanat oil immersion, a self built achromat based on a #1973 blank including the 1.4 top lens( no immersion requirement determined, although the top lens requires oil in order to obtsin 1.4 N.A.) and a self built apochromat based on a # 1973 blank including the 1.4 top lens ( same immersion status as the former).
The results were in order of preferance in actual use with an N.A. 1.30 plan fluor objective.
Dry ; 1) self built achromat, 2) .90 achromat aplanat 3) 1.25 abbe aspheric, 4) 1.4 achromat aplanat 5) self built apochromat. The preferance here is based on the higher luminance of the self built condenser and the fact that it appears to be a slightly higher N.A., perhaps as high as .95.
Water: 1)self built apochromat. 2) self built achromat. 3) 1.25 abbe aspheric. 4) 1.4 achromat aplanat. 5) .90 achromat aplanat. The preferance here was based on luminance, colour correction and the ability to achieve Köhler. None of the condensers with water were better than several others dry or most oiled. Some had odd colour artifacts.
Oil : 1) 1.4 achromat aplanat. 2) 1.25 abbe aspheric 3) self built apochromat. 4) self built achromat. 5) .90 achromat aplanat.
Order of overall preferance. 1) # 1973 1.4 N.A. achromat aplanat oiled 2) self built achromat , dry 3) # 1970 1.25 abbe aspheric oiled 4) # 1202 .90 achromat aplanat dry 5) # 1970 1.25 abbe aspheric dry.
Just because a condenser is an immersion condenser, that doesn't mean that another immersion medium will work better than air.