DESCRIPTION | HISTORY |
Nelson's Cassegrain Dark Ground Illuminator. This condenser, which fits the same housing as the Holos Immersion Paraboloid, was also called
Nelson's Reflex Condenser. This illuminator was designed for slides of 1 to 1.2 mm thickness. It was supplied with 2 different diameter stops, although only one labeled
16is present with this example. This condenser has the advantage of allowing the full N.A. of oil immersion objectives to be used with N.A. up to 1.40. This type of high power dark ground condenser is much less complex and easier to manufacture than the cardioid type*, though the latter is usually optically superior.
horseshoefoot and supported on a single pillar, so as not to interfere with substage adjustments during the, (then) delicate operation, of photomicrography with high power objectives. At the same time, many others preferred the horizontal position for photography. For this reason, his stand was also offered with the more stable English tripod foot which provided a much more stable stand for photography in the horizontal position. Many more examples with an English tripod exist than with the horseshoe foot, as the tripod quickly became more popular.
VAN HEURCK NO. 4, 'A' MODEL | ||
DATES | STANDARD FEATURES |
OPTIONAL FEATURES |
---|---|---|
1893 | Horseshoe foot, single draw, Mechanical Stage with separate controls for horizontal and vertical motion which rotates but not a full 360 degrees, Substage Fine Adjustment, Projecting upwards in back of stage, clamping lever for inclination Joint. The mechanical draw-tube length can vary from 160 to 260 mm. |
Tripod foot, Binocular Body,
Centering Screws
to stage with clamping, Rackwork rotation to stage, Divisions to stage,
Divisions to Horizontal and Vertical movements of stage, Rackwork
rotation to sub-stage, Clamping of
substage centering, |
1896 | The 'A' Stand is no longer offered in the catalog | |
VAN HEURCK NO. 4, 'B' MODEL | ||
DATES | STANDARD FEATURES |
OPTIONAL FEATURES |
1893 | Double Draw, with one Mechanical Draw tube, otherwise same as 'A' but with the extra draw-tube , the mechanical tube length has a longer range of from 142 to 310 mm. | Tripod Foot, Binocular Body |
1896 | Tripod Foot now standard, otherwise same as 1893 | same as 1893, except now the Horseshoe foot was optional |
VAN HEURCK NO. 1 | ||
DATES | STANDARD FEATURES |
OPTIONAL FEATURES |
1900 | Same as Van Heurck B of 1896 | Same as 1896 with additional option of Strnger's fine adjustment |
1902 | same | Same but also the Males-Watson fine adjustment and the Spindle head fine adjustment AND hinged substage which can be turned aside out of the optical axis |
1906 | same | same |
1912 | same except now the substage fine adjustment is an option | Choice of above or below stage substage fine adjustment |
1918 | same except now all Van Heurcks have hinged substage standard, which allows the substage to be turned aside and out of the optical axis | same as 1912 |
1921 | same as 1912, but now the substage bar extension sliding on dovetail to allow greater range of accessories of different heights as was previously only offered for the Grand, then the Circuit stage, is now offered for all Van Heurcks | |
1923 | ||
VAN HEURCK CIRCUIT STAGE MODEL | ||
DATES | STANDARD FEATURES |
OPTIONAL FEATURES |
1900 | Identical to No. 1 but with complete stage rotation | Identical to No. 1 |
1906 | Same as 1900 | Same as 1900 |
1912 | same except now the substage fine adjustment is an option | Choice of above or below stage control of substage fine adjustment |
1918 | same except now all Van Heurcks have hinged substage standard, which allows the substage to be turned aside and out of the optical axis | same as 1912, but now the substage bar extension sliding on dovetail to allow greater range of accessories of different heights as was previously only offered for the Grand |
1921 | same as 1918 | same as 1918 |
1923 | ---- | ---- |
VAN HEURCK GRAND MODEL | ||
DATES | STANDARD FEATURES |
OPTIONAL FEATURES |
1896 | Identical to the Van Heurck 'B' Stand, with the addition of concentric controls for the mechanical stage, and extension of the stage and arm forward to allow complete stage rotation and larger overall size. | Identical to Van Heurck 'B' model. |
1900 | Identical to Circuit stage Model, but larger | Identical to Circuit stage model but optionally the same stage as the No. 1 instead of fully rotating, reduced the price by 3 pounds. |
1902 | Identical to Circuit stage Model, but larger | Identical to Circuit stage model
but optionally the
same stage as the No. 1 instead of concentric controls, reduced the
price by 3 pounds. Also option of Stringer's fine
adjustment, or
Males-Watson Two speed fine adjustment, or Spindle Milled-head fine
adjustment, all at extra cost. Optional hinged substage so it can be swung out of the optical axis. Also a substage bar extension sliding on dovetail to allow greater range of accessories of different heights. |
1906 | Identical to 1902 | Same as 1902 but also offered the Scop Mechanical Stage instead of the usual circuit stage, price the same as the standard model. |
1912 | same | same as 1906 |
1918 | same except now all Van Heurcks have hinged substage standard, which allows the substage to be turned aside and out of the optical axis | |
1921 | Same | Side Limb or Horizontal fine adjustment for same price. |