Darton Spherometer, 1930, telescope optics, mirror lenses
Working Darton Spherometer for measuring the curvature of a telescope mirror or lens.
"The usual form consists of a fine screw moving in a nut carried on the center of a small three-legged table or frame; the feet forming the vertices of an equilateral triangle. The lower end of the screw and those of the table legs are finely tapered and terminate in hemispheres, so that each rests on a point. If the screw has two turns of the thread to the millimetre the head is usually divided into 50 equal parts, so that differences of 0.01 millimeter may be measured without using a vernier. A lens, however, may be fitted, in order to magnify the scale divisions. A vertical scale fastened to the table indicates the number of whole turns of the screw and serves as an index for reading the divisions on the head.
A contact-lever, delicate level or electric contact arrangement may be attached to the spherometer in order to indicate the moment of touching more precisely than is possible by the sense of touch. To measure the radius of a sphere—e.g. the curvature of a lens—the spherometer is leveled and read, then placed on the sphere, adjusted until the four points exert equal pressure, and read again. The difference gives the thickness of that portion of the sphere cut off by a plane passing through the three feet." Source: Wikipedia
Condition
The Darton Spherometer is working order.
Cosmetic signs of use.
Included in the sale
Darton Spherometer
Dimensions
Height: 18cm
Width: 6,4cm
Our service
We have been selling vintage astronomical instruments for over more than 10 years.
I'm a amateur astronomer myself and all instruments I sell are in good working condition.
I test all the telescopes under the stars and know the possibilities of each instrument
All the instruments are controlled and cleaned before shipping.
The necessary reparations are done.
If possible missing parts are replaced.
If not, read the item description carefully for possible defects.
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The advantage is you know exactly what you're buying.
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We have experience in shipping large instruments up to the unique and complete 6" Unitron - Polarex
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Returns are possible.
The buyer needs to know how to use the instrument in the right way.
There is a limited warranty because we don't sell new instruments but used vintage instruments.
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More information
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