The First 300 Years of Binocular Telescopes.
Peter Abrahams.   May 2002.

What we call a binocular is a binocular telescope, two small prismatic 
telescopes joined together.  They are made in larger sizes as well, and in 
historic times many telescope configurations could be purchased in a 
binocular form.  Hand held binoculars developed into a household item, but 
they will arbitrarily be considered a separate product.  Binocular telescopes 
in this context are typically tripod mounted, twin tube, long physical length 
and long focal length.  Very early or important models that are exceptions 
will also be considered.  Both erect image terrestrial telescopes, and 
inverted image astronomical telescopes have been made in a binocular 
configuration.  Refracting, reflecting, and catadioptric binocular 
instruments have been used, of configurations including Newtonian, Gregorian, 
Cassegrain, and Maksutov.  They all share the considerable difficulty of 
matching and aligning two images to the extreme precision required by 
binocular vision.  They also share their intended use, for all were likely 
visual instruments and were of little scientific use, at least after the age 
of Galileo.

Binocular telescopes were conceived during the earliest days of the 
telescope.  When spectacle maker Hans Lippershey developed his telescope, it 
became the earliest telescope whose documentation survived to the present 
day, and is considered the earliest known telescope, although probably not 
the first to be created.  The record of his invention makes such a good story 
that one is tempted to think it became embellished over the years.  

When Lippershey applied for a patent on his instrument in 1608, the 
bureaucracy in charge, who had never before seen a telescope, asked him to 
build a binocular version of it, with quartz optics, which he is reported to 
have completed in December 1608.  It was probably 3 or 4 power, and an inch 
and one half or less in aperture.  Henry King quotes a government document, 
“On the petition of Hans Lippershey,...It was resolved, that some of the 
Assembly do form a committee, which shall...enquire of him whether it would 
not be possible to improve upon it, so as to enable one to look through with 
both eyes...”  First a monocular and then a binocular telescope were tested.  
These instruments passed inspection, but the patent was denied because other 
telescopes were already known.  Lippershey was asked to make two more 
binoculars, and all three were finished inside of five months.  On request, 
he lowered his price for the three binoculars from 1000 florins to 900 
florins, which might be about equal to 1000 dollars today, to the poor man of 
today.  The binocular telescope is therefore as old as the monocular 
telescope, and in fact if this record is correct, 3 of the 4 earliest 
documented telescopes were binoculars.  The immediate regression of the 
telescope into the popular monocular form is seen as an atavistic reversion 
by the advocates of the binocular, but to dwell on these losses is fruitless.

Galileo’s instruments were probably of considerably better quality than their 
predecessors, and his surviving lenses have been tested with very good 
results.  Many references on Galileo describe a binocular telescope of his 
design, but some recent Galieo studies disagree concerning his construction 
of this binocular. 

Giovanbattista de Nelli, in his 18th century collections of Galileo’s letters 
and other works, wrote that in 1618 Galileo constructed a helmet with a frame 
containing two small telescopes, to be used on board a ship, and named it the 
celatone.  There are many references to the helmet in Galileo’s writings, 
including construction, testing, presentation to sponsors and ambassadors, 
and the development of a gimbaled observer’s chair to counteract the motion 
of the ship.  Instrument historian Silvio Bedini summarizes the known 
documentation and accepts the notion that the helmet was binocular.  However, 
telescope historian Albert van Helden notes an1881 Italian history of 
“Cannocchiali Binoculari”, by Antonio Favoro, in which it is claimed that the 
helmet had a single telescope.  Van Helden believes that Galileo did not use 
a binocular instrument, and the idea should be regarded as less than certain, 
pending further research.

Other writers describe how one was built in 1616 or 1617, tested aboard ships 
throughout 1617, and one celatone was presented to the Spanish ambassador to 
Italy.  In 1636, Galileo described how longitude could be ascertained by 
observation of Jupiter’s moons, and described the celatone in the same text.

Ottavio Pisani, an Italian amateur astronomer, wrote to Galileo in September 
of 1613, discussing a binocular telescope, but his other letters to Galileo 
and his publications do not mention it.

Daniele Chorez made optical instruments in Paris, and is thought to have made 
a binocular telescope by 1625.  A notice publicizing and depicting his 
microscopes and telescopes shows the binocular.  The left telescope is 
attached to a frame, and the interocular adjustment is accomplished with the 
right tube.  A screw was attached to the frame to use for supporting the 
binoculars on a fixed object.

The notice was found in 1880 by Gilberto Govi, who wrote an article with the 
most intriguing title, “Nuovo Documento Relativo alla Invenzione dei 
Cannocchiali Binocoli”.  (Cannocchiali, or cannon, being the contemporary 
Italian term for these very earliest telescopes).

Anton Maria Schyrle, originally from Rheita, Bohemia, Rheita lived as a 
priest in Bohemia, Belgium and Italy from 1597 to 1660.  He developed several 
inverting and erecting eyepieces, and is credited with bringing into use the 
terms 'ocular' and 'objective'.   Rheita published a very influential book on 
optics in 1645, his Oculus Enoch.  The book contained descriptions of 
erecting eyepieces:  "Objects, reversed by two convex lenses, are uprighted 
beautifully by three."  Also described was this system:  "If you position two 
convex objectives... in the tube so that they can be approached or distanced 
within the tube....then you will have to your great joy, ten or twenty tubes 
of different length in one tube, so that, the more you distance the tubes, 
the larger and larger the object will appear, and vice versa."  A moon map 
from Oculus Enoch is not as accurate as some contemporary lunar charts but it 
the first depiction of the moon as seen in an inverting telescope.   Another 
engraving seems to show a grinding machine.  And finally this volume 
contained a long section on binocular telescopes, which was the single 
greatest influence on other makers of these instruments in the century to 
come.  None are illustrated, but the form he describes became the standard 
construction for many years.

Rheita wrote, in Latin, translated into German and then translated into 
English:  "About the manufacturing of the binocular tube.  So, a tube in 
wider form is constructed so that, when placed in front of the eye, it covers 
both eyes with its large form.  From the upper rim, which goes in front of 
the eye, an arc should be cut out, so that it touches the forehead.  At the 
lower rim it should be caved in, at the middle, in similar fashion so that 
there is room for the nose.  In this way the eyes in relation to the convex 
oculars always have a solid hold and keep their position, which has to be 
totally guaranteed.  Then one of the tubes should be provided with its small 
oval glare shield, as we have learned above, this must occur in the binocular 
tube.  This done, you need to have two convex objectives, manufactured in the 
same dish, with completely equal quality, dimension and thickness, and also 
two oculars absolutely equal and also done in the same form.  These are put 
into the tube so that the centers of the ocular glasses coincide with each 
pupil of your eyes, so that the centers are as far apart from each other as 
one pupil is distanced in your eye from the other (which you can easily find 
out with the help of a compass and a mirror).  The two objective lenses 
should be a little closer together, depending on whether the object is closer 
or farther away from the position of the observer.  The farther it is, the 
more the convex objectives in the tube have to be distanced from each other, 
and the closer it is, so the objectives have to be closer, too.
"But this can be achieved for each distance of the object more correctly and 
more comfortably with one little cogwheel between both lenses, which is so 
cleverly placed with its teeth at the top and the bottom, with a moveable 
disc, and the toothed protuberances pull them together or push them apart.  
In this way, the convex objectives, fastened to the little disks made of 
brass or other hard material, can easily be distanced or pulled together for 
any distance of the objectives.  And by chance, in this way even the 
distances of the objectives are accurately measured by the eye.
"Consequently, the four convex lenses in this binocular tube (or two concave 
and two convex, in the usual way and for the viewing of terrestrial objects), 
have to be positioned so that each of the two light cones, which are to be 
sent through those glasses, from the object side on both sides into the eyes, 
is collected outside the tube in a wider cone and in a single focus and so 
all points of the object are not doubled, but unitedly viewed, as also 
happens with the usual telescopes."
"Things appear more alive with the binocular telescope, doubly as exact so to 
speak, as well as large and bright.  With the monocular, they appear at most 
half dead, strongly unfocused, and made smaller.  "
[Schyrlaeus, Antonius Maria (de Rheita).  Oculus Enoch et Eliae sive radius 
sidero-mysticus.  Antwerp.  1645]

Francois Lassere, the Capuchin Pere Cherubin d’Orleans, developed the 
binocular telescope in a characteristic form, separating the tubes with a 
metal frame and placing this in cardboard boxes that extend by sliding the 
smaller box from within the larger.  Cherubin made about 30 of these in the 
1660s and 1670s,and there are a few of them in European museums.  In 1671, he 
published his La Diotrique oculaire, which described both binocular 
microscopes and telescopes.  His second book,  La vision parfaite, of 1677, 
showed several of his designs for hand held binoculars, as well as binocular 
telescopes and instruments by Cherubin and de Rheita.  Cherubin made an 
unusual ‘marine binocular’, now in the Museum of Science in Florence.  (It is 
unclear whether this is the complete instrument, or just the oculars.).  
This museum also exhibited in 1988 a four draw, ornamented cardboard 
binocular attributed to d’Orleans.

Johannes Zahn’s Oculus Artificialis Teledioptricum sive Telescopium, was 
published in Nuremberg in 1685.  An unusual binocular is depicted in that 
volume.  The string between the tubes can be pulled taut to approximate 
collimation, a clever and somewhat effective method of alignment.

J.M. Dobler made optical instruments in Berlin circa 1700, and two of his 
binocular telescopes are in Moscow’s State Historical Museum.  One is a 
cardboard oval tube, parchment covered, 88 cm long, with objectives and 
oculars in wooden lens cells.  The other is a 75 cm cardboard rectangle, 
leather covered, with wood lens cells and leather lens caps, with the 
inscription “Binoculum oder doppeltes feld perspectiv”.

Pietro Patroni was a mid 18th century maker of microscopes and telescopes in 
Milan, Italy.  His binocular telescopes closely follow those illustrated in 
La vision parfaite by Cherubin d’Orleans,.  Both makers decorated their 
instruments with elaborate gilt tooled leather, presumably because many of 
their customers were noblemen who were purchasing collector’s items or 
conversation pieces.  This binocular telescope made by Patroni in 1714 is in 
the Deutsches Museum in Munich.  The silver ocular covers swing open to 
reduce glare.  The objectives have about 12 mm of clear aperture, with about 
10 times magnification, and the three lens erecting system has no aperture 
stop.  Another dated 1719 is in the Pierre Marly collection in Paris.  This 
is 30 cm in length, covered with fishskin and vellum, and the key is used to 
adjust focus.  The Museo di Storia della Scienza in Florence possesses a 
Patroni binocular from the 1670s.  Interocular adjustment is accomplished 
with adjusting screws that give four settings for eye spacing.  His 
instruments were highly regarded in his time, and contemporary British 
instrument salesmen suggested their telescopes could compare with “those of 
the celebrated Pietro Patrone at Milan”.

Milan had another maker of binocular telescopes around 1750.  Francois 
Baillou made both monocular and binocular forms of microscopes, telescopes, 
and opera glasses.  He made deep green telescope lenses for solar 
observation, and seems to have used a star diagonal he called his ‘reflection 
system’, though it is unclear if it was a prism or mirror.  His binocular 
telescopes are shown on his trade card and his pamphlets.  Milan seems to 
have fostered a creative and productive optical industry in the 18th century, 
it has been the subject of articles by ATS member Alberto Lualdi of the 
Universita di Pavia, appearing in the Bulletin of the Scientific Instrument 
Society.

Lorenzo Selva was part of a family of instrument makers in Venice through the 
1700s.  In his Dialoghi Ottici Teorico-Pratici (1787), many instruments are 
described and depicted, including telescopes and binoculars.

A binocular telescope with 50 mm objectives was made by the shop of Peter 
Dollond, circa 1790.  This instrument is far more advanced than earlier 
designs.  Interocular adjustment looks as if it is accomplished with the rod 
on the side of the tube, engaging both the objectives and the oculars in 
their tracks, presumably with a rack and pinion.  This beautiful telescope 
could possibly have triplet objectives of matched focal length, although that 
might require virtuosity beyond even the best of the 18th century opticians.

The optical designs of many of these instruments are not recorded. Most would 
have used Galilean optics, but some might have used a convex eyepiece to 
allow higher powers.  These Keplerian optics would have been useful in an 
astronomical instrument, and their widespread use in telescopes insures that 
at some point a binocular telescope was constructed on that principle, 
despite the difficulties in collimation that result from higher powers.  
Image erecting systems using lenses had been in wide use since they were 
devised by Schyrle de Rheita circa 1750, and no doubt some double terrestrial 
telescopes were made in that way as well.  

All of these twin telescopes were refractors, and the first reflecting 
binocular was an engineering milestone.  Cassegrains and Gregorians have 
longer focal ratios and higher magnification, making it far more difficult to 
collimate the two tubes.  Their larger diameter necessitates multiple 
reflections at the ocular to bring the eyepieces to interpupillary distance.  
A binocular Gregorian was proposed by Robert Smith in his A Compleat System 
of Optiks, to improve the poor optical quality of the binoculars he had used.  
Smith noted that Edward Scarlett of London made binocular telesopes, of the 
form used by d’Orleans.  I know of no early binocular Gregorians or 
Cassegrains.  A binocular Newtonian can have a focal ratio lower than the 
refractors of these times, and the lower magnification can make alignment 
easier.  However, the perpendicular configuration of a Newtonian considerably 
complicates the design of a binocular. 

A twin Newtonian was proposed by M. Vallack, and described by John Herschel 
in The Telescope, published in 1861, but one had not been built at that time.  
Vallack’s design placed two Newtonians adjacent to each other, the secondary 
of the far tube reflecting its light over the open end of the near tube.  The 
far tube has its primary mirror mounted closer to the secondary than does the 
near tube, to keep the foci of the primaries at the same level.  Herschel 
devotes 7 pages to the binocular telescope, describing the typical pair of 
refractors, that have been used for viewing the sun, moon, and planets; 
“though without any very great practical advantage”.

Herschel also presages the modern battery commanders stereoscopic rangefinder 
by describing a stereo-telescope that had been built by A.S. Herschel in 
1855, and another described by M. Helmholz in 1859.  These instruments are 
two telescopes, with the objectives spaced prehaps 18” apart, each directed 
to an eyepiece via mirrors or prisms.  The widely spaced objectives give an 
greatly enhanced sense of depth perception.

Alvan Clark and Sons made binocular telescopes, with objectives of 3 or more 
inches in aperture, according to Louis Bell, who wrote that many such 
instruments were made.  The estimated quantity is reduced to a few binoculars 
by Warner & Ariail.  Examples of Clark binocular telescopes could apparently 
be found at the Mount Tom Summit House and the Mount Washington Hotel in 
1920, when Bell wrote “The Telescope”.  A four inch binocular, of 60 inch 
focal length, with Porro I prisms and wide angle Kellner oculars is shown. 

During the Civil War, the U.S. Naval Observatory encouraged the optical 
manufacturers of the Union states to produce instruments for war use, 
including hand held Galilean binoculars.  The Clarks were asked in 1864 to 
make binoculars that combined a wide field with high magnification.  
Binoculars were at this point the only instrument that the military was 
forced to purchase from foreign countries.  Robert Tolles supplied a small 
quantity of field glasses that were judged better than the European models, 
and Henry Fitz and Alvan Clark produced one binocular each.  The Clark glass 
was tested in February of 1865, and judged better than the Fitz product, but 
the end of the war soon after that probably indicates that only one 
instrument was completed.  None of these binoculars are currently known to 
exist.

A binocular of 6 1/4 inch aperture, and 92 1/4 inches focal length was made 
by the Clarks for Daniel Webster Edgecomb, an amateur astronomer in Mystic, 
Connecticut who took an active interest in binocular observation.  Edgecomb 
wrote “ I have long been interested in binocular telescopes, and have put 
many together with objectives from 2 1/4 inch upwards.  When in England I had 
Sir Howard Grubb make for me one of his binoculars with prismatic eyepieces, 
and object-glasses five inches in diameter.”  There is no further 
documentation of Grubb’s binoculars, including the new book length history of 
his firm.  Edgecomb describes the instrument as “somewhat remarkable” in use, 
noting that the focal lengths of the two objectives differ by about one tenth 
of an inch.  When Edgecomb commissioned Clark to make his 6 1/4 inch 
instrument, Clark estimated he could produce a pair of lenses with focal 
lengths matched to one hundredth of an inch.  The two lenses were cut from 
the same pieces of glass, and Edgecomb found them to be indistinguishable, 
with a focus of 94 inches and identical color correction.  He wrote a long 
article describing his use of the Clark binocular telescope, and extolling 
the virtues of this type of observation.  He quotes Dr. Kitchener as noting 
that binculars were used in his day in part because of the difficulty in 
making large objectives for single telescopes.

Daniel Edgecomb had a brother who was a telescope maker and made binocular 
instruments.  William Cary Edgecomb, who lived from 1845 to 1906 in Mystic, 
Connecticut, advertised his terrestrial binocular telescopes, at least 3 of 
which survive.  One has 5 1/4 inch objectives mounted in cells that allow for 
collimation of the two tubes.  Another has 2 3/4 inch objectives.  A fourth 
binocular that is unsigned but was found in Mystic has 2 inch objectives.

 R & J Beck of London were one of the finest manufacturer of optical 
instruments, listing an 1 1/2 inch aperture, 15 power telescope in their 1867 
and 1881 catalogs, noting its applicability by the sea shore, where the user 
could scan the horizon

The most in depth work on binoculars of all types is Moritz von Rohr’s 1920 
work, Die Binokularen Instrumente.  This 303 page work has not been surpassed 
as an overview of optical instruments designed for visual use with both eyes.

The appendix includes this overview of binocular telescopes to 1907.  Von 
Rohr discusses double terrestrial telescopes, with lens erecting systems, 
noting that they were in early use but by the later 1800s in Germany were 
unavailable due to the preponderance of Galilean binoculars.  By 1854, P. G. 
Bardou in France sold double terrestrial telescopes with center focus and a 
hinge for interocular adjustment.  These were 16 power and had 27 mm 
objectives.  Von Rohr also discusses an 1870s vintage single objective 
telescope with a binocular viewer that utilized two rhomboid prisms to direct 
the light to two oculars.  This design is from Lafleur and Roulot, Un systeme 
de lunette biprismatique, but even in 1870, this was not a new idea, 
according to von Rohr.  Prisms came into use in higher power magnifying 
optical instruments at a later date than lenses because they require a higher 
standard of glass than do lenses.  Light traverses a lens through one 
direction only, and striae in the glass parallel to that direction have 
little effect on the image.  Light traverses a prism in two directions, and 
for many years the glass manufacturers could not obtain prisms that were free 
of striae.

Over in England, W. H. Thornwaite designed a telescope where a single 
reflecting objective used a partially reflecting secondary to direct the 
image to the oculars.  This was published in 1877, and a suggestion was added 
that the Wenham prism system, used in microscopes, could also be used in 
telescopes.  (Monthly Notices)

In 1881, H. Goltzsch in Germany designed and built an astronomical double 
telescope, using 74 mm objectives.  One tube was placed parallel and partly 
behind another, so that the viewer could see only half of one tube, in order 
that the optical axes of the two scopes could be brought to 60 mm apart.  One 
secondary mirror was more distant from the observer than the other, and small 
telescopes were placed in front of the oculars to equalize the images.  If I 
translated von Rohr accurately, these are unit power scopes of different 
focal lengths.  Interocular distance was adjusted by rotating the main 
telescopes around their axes, so that a wider interocular caused convergence 
of the eyes.  He later replaced the secondaries with equilateral 60 degree 
prisms, to alter the observing angle.  Further work involved replacing the 
Huyghenian ocular and combining a negative lens with the small telescopes.  
This seems to have given pseudoscopic images of terrestrial objects.  This 
aspect of binocular design can be seen by combining two simple non-erecting 
telescopes (finder scopes) into a binocular, which gives images that are 
reversed in depth.  Goltzsch solved the problem by placing an Amici prism 
with each ocular.  Goltzsch was a prolific author, publishing on binocular 
microscopes, telescopes, stereoscopes, and oculars.

The modern prism binocular began with Ignatio Porro’s 1854 Italian patent for 
a prism erecting system.  Throughout the 1860s, Porro worked with Hofmann in 
Paris to produce monoculars using the same prism configuration used in modern 
Porro prism binoculars.  Other early makers of Porro prism optics were 
Boulanger (1859,) Emil Busch (1865,) and Nachet (1875).  Some of these makers 
produced prism binoculars.  A combination of poor glass and unrefined optical 
design and production techniques resulted in the failure of all these 
ventures.  These monoculars are all very scarce today, and it is unknown if 
any of the binoculars survive.

The German optical designer Ernst Abbe displayed a prism telescope at the 
1873 Vienna Trade Fair.  Designed according to Porro’s principles, but 
without knowledge of the earlier work, Abbe’s new innovation was to cement 
the prisms.  He then set aside the idea and went on to develop the 
theoretical basis of the modern microscope.  His association with Otto 
Schott, glassmaker, and Carl Zeiss, instrument maker, resulted in a 
spectacular series of innovations by the German optical industry.  The first 
high quality modern binoculars were sold in 1894, a product of the optical 
design of Ernst Abbe and the production techniques of Carl Zeiss.

This paper draws to a close at 1900, but a few highlights of this century 
will be presented because of their historical importance or optical interest.  
For many years, Zeiss made a spectacular series of binocular telescopes, of 
very high quality and extremely immodest pricing.

A 5 x 36 binocular from 1919 and by Dollond is unusual because it is without 
erecting system.  It is a military glass, probably used for signaling.  In 
the days of uncoated optics, every glass-air surface would reduce the 
transmitted light by about 5 percent.  In a complex instrument like a 
binocular, transmitted light could be reduced by half.  By eliminating the 4 
glass-air surfaces in a prism erecting system, or the up to 8 surfaces in a 
lens erecting system, this Dollond binocular could give a noticeably sharper 
image that was also free of the ghost images that reflections can produce.  
Steinheil of Munich made a similar 5 x 34 binocular circa 1902, and Zeiss 
sold a similar 10 x 50 in 1928.  These are not astronomical instruments, but 
they use optical systems identical to a refracting telescope with a Keplerian 
ocular.

The history of the telescope is intertwined with such elevating subjects as 
the development of astronomy, but the major improvements to the binocular 
have generally been motivated by the forces of war.  World War II in 
particular saw some enormous improvements to the binocular, from the Germans, 
the Americans, and the Japanese alike.  A Zeiss 50 x 130 is a picturesque 
instrument that would make a wonderful astronomical tool.  The largest German 
binocular was the 20 or 40 x 200, significant for its size and weight and 
also for the extremely complex mechanical system built into the prism housing 
to correct for image rotation caused by revolution of the prism.

The largest Japanese binocular was the 50 or 83 power, by 250 mm objective, 
300 pound instrument.  The original twin ocular was replaced with this single 
40 power eyepiece.  Two of these were made by Nikko, and were used at the 
Russian-Japanese front.  One was destroyed, but one survives in Tokyo at the 
National Science Museum.

A binocular was designed by Albert Bouwers in the early 1940s in Hollond.  It 
is a 20 x 60 that uses what he calls his improved Cassegrain optical system, 
which has become known as the Maksutov.  Bouwers also designed a 12 x 35 
Gregorian Maksutov binocular.  These two very innovative instruments are 
shown in Bouwers’ 1946 volume, Achievements in Optics, which is full of other 
varieties of optical inventiveness.

A binocular viewer was made during the 1950s by Gerard Kuiper, for use on the 
Yerkes 40 inch refractor, and the McDonald 82 inch reflector.  I don’t know 
of other instruments by Kuiper, but I hope they are safe from harm.

The famous Amateur Telescope Making trilogy from Scientific American saw its 
first volume in 1935.  By the 1967 edition of this volume, it included this 6 
inch binocular Newtonian by Hilmer Hanson of Holdredge, Nebraska.  This 
project seems to have been deleted from the recent reprint of the ATM series.  

However, there is a renaissance of binocular construction among amateur 
telescope makers.  The largest I am aware of is this 20 inch twin Newtonian, 
but there are at least a few dozen amateur made twin telescopes to be found 
at gatherings of stargazers.  These can be refracting, Cassegrain, or 
Newtonian; and there is at least one off axis Gregorian binocular.  The views 
these instruments give are spectacular, for they truly allow the observer to 
forget there is an instrument between the eyes and the heavens. 
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BIBLIOGRAPHY

Bedini, Silvio; The Instruments of Galileo Galilei.  Chapter 13 of Galileo, 
Man of Science, Ernan McMullin, ed.  Princeton Junction, The Scholar’s 
Bookshelf, 1988 (1967).  pp279-280.

Bell, Louis; The Telescope.  N.Y., McGraw Hill, 1922.  pp2-3.

Edgecomb , Daniel W. On the Performance of a 6 1/4 inch Binocular Telescope. 
Popular Astronomy, vol. 10, pp523-31, 1902.

Favoro, Antonio.  Sulla Invenzione dei Cannocchiali Binoculari.  Atti della 
Reale Accademia delle Scienze di Torino.  16 (1881).

Goltzsch, H..  Astronomisches Doppel-Fernrohr.  Zeitschrift fuer 
Instrumentenkunde.  1881.

Govi, Gilberto.  Nuovo Documento Relativo alla Invenzione dei Cannocchiali 
Binocoli.  Bulletino di Bibliografia e di Storia delle Scienze Matematiche e 
Fisiche. Vol. XIII, 1880, pp. 471-477.

Helden, Albert Van.  The Invention of theTelescope.  Philadelphia, The 
American Philosophical Society, 1977.  Transactions of the APA, vol. 67, part 
4.  pp.20-21.

Herschel, John.  The Telescope.  Edinburgh, Adam & Charles Black, 1861.  
pp116-122.

King, Henry.  The History of the Telescope.  London, Charles Griffin, 1955.  
p31.

Lafleur and Roulot.  Un systeme de lunette biprismatique. 1873.

Lualdi, Alberto. Pietro Patroni, an 18th century Milanese Optician.  Bulletin 
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Marly, P.  Spectacles and Spyglasses.  Paris.  1988

Nelli, Giovanbattista de.  Saggio di storia letteraria fiorentina del secolo 
XVII.  Lucca.  1759. 

Nelli, Giovanbattista de.  Vita e commercio letterario di Galileo Galilei.  
Lausanne.  1793.  (collections of Galileo’s letters and other works)

d’Orleans, Pere Cherubin.  La Diotrique oculaire, ou la Theorique, la 
positive, et la mechanique, de l’Oculaire dioptrique en toutes ses especes.  
Paris. 1671.  pp210-213.

d’Orleans, Pere Cherubin.  La vision parfaite.  Paris.  1677-1681. 2 vols. 
Tome I, p. 102.

Rheita, Antonius Maria Schyrlaeus de.  Oculus Enoch et Eliae sive radius 
sidero-mysticus.  Antwerp. 1645.

Rohr, Moritz von.  Die Binokularen Instrumente.  Berlin, 1920.

Schyrlaeus, Antonius Maria (de Rheita).  Oculus Enoch et Eliae sive radius 
sidero-mysticus.  Antwerp.  1645

Seeger, Hans; Feldstecher: Fernglaser im Wandel der Zeit.  Borken, Bresser 
Optik, 1989.  pp29-31.

Thornwaite W.H..  Description of an improved altazimuth stand for reflecting 
telescopes, with a new form of binocular eyepiece. Monthly Notices of the 
RAS, 87.  pp3-4.  1877.

Vallack.  MNRAS  8 (1848) 139

Warner, Deborah Jean and Robert Ariail.  Alvan Clark & Sons, Artists in 
Optics. Richmond: Willman Bell, 1995.

Zahn, Johannes.  Oculus Artificialis Teledioptricum sive Telescopium. 
Nuremberg, 1685

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