Who invented the blink comparator?

Who invented the blink comparator?

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The Wikipedia page for the blink comparator fails to mention who invented it. Many other pages extol the importance of the device, but we cannot find any mention of an inventor.

Wikipedia does mention that Ben Mayer invented the The Projection Blink Comparator (PROBLICOM), which is a low-cost improvement on the blink comparator. However, he did not invent the original device.

It would appear to have been developed by Carl Pulfrich working for Zeiss in 1904.

Alternatively Max Wolf in 1900 again working with the Zeiss company.

Looks like the idea was Wolf's and the realisation Pulfrich's. From the second link we have:

Wolf was a codeveloper of the stereo comparator together with Carl Pulfrich from the Zeiss company. The stereo comparator consists of a pair of microscopes arranged so that one can see simultaneously two photographic plates of the same region taken at diff erent times. Wolf seems to have experimented with such techniques as early as 1892, but without success. When Pulfrich approached him to adapt the technique from geodesy to astronomy, Wolf was delighted. A steady exchange of letters followed. Wolf and Pulfrich then worked together to analyze the rapidly growing accumulation of photographic plates. Tragically, Pulfrich lost one eye in 1906, preventing him from using the stereographic tool from then on.

A blink comparator was a viewing apparatus used by astronomers to find differences between two photographs of the night sky. It permitted rapidly switching from viewing one photograph to viewing the other, "blinking" back and forth between the two taken of the same area of the sky at different times. This allowed the user to more easily spot objects in the night sky that changed position. It was also sometimes known as a blink microscope. It was invented by physicist Carl Pulfrich at Carl Zeiss AG, then constituted as Carl-Zeiss-Stiftung, in 1904

I don't know if the loss of an eye (mentioned in this answer) is related, but there is a one-eyed embodiment described in the 1909 patent US941812, Telemeter for two successive observations.

"Another arrangement of the telemeter, in which the two images are produced successively in a common image field filling the entire ocular field, seems to be still more advantageous."

Thus it seems the comment at the bottom of the the first page in this article might not be 100% correct. I don't know the date, but the one-eyed blink comparator in Wikipedia looks pretty darn old!

"Tragically, Pulfrich lost one eye in 1906, preventing him from using the stereographic tool from then on."

The full quote can be found in the other answer.

above: "English: Blink comparator in the Meridian hall of the Helsinki observatory. Made by Carl Zeiss in early 20th century." from here

above: from Finding Pluto with a Blink Comparator

The Discovery of a Planet, Part 6: From Pluto to Sedna

74 years after Clyde Tombaugh discovered Pluto as a faint dot on a pair of photographic plates, a modern group of astronomers made another remarkable discovery. On March 15, 2004, Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale announced the discovery of Sedna – the furthest object ever detected in the Solar System. With a diameter of 800 to1100 miles, it is also the largest Solar System object discovered since Pluto, which comes in at 1400 miles.

The Samuel Oschin Telescope at Mount Palomar This automated 48 inch telescope is used by Michael Brown's group in their search for giant Kuiper belt objects. Sedna was discovered with this telescope. Image: Mount Palomar Observatory

Like Tombaugh in 1930, Brown and his colleagues are conducting a telescopic survey of the outer reaches of the Solar System in search of planet-like objects. On the occasion of the 75th anniversary of the discovery of Pluto, we decided to find out how much things have changed and how much they have stayed the same.

“We have it easy” Brown said when asked to compare his search to Tombaugh’s 75 years ago. We have to agree, and here’s why:

    The modern search is almost completely automatic. The 48 inch Samuel Oschin telescope at the Mount Palomar Observatory near San Diego is operated robotically, without the presence or involvement of any of the researchers. In 1930 Tombaugh had to spend each observing night in the unheated dome operating the telescope.

Understandably, Brown considers Tombaugh’s achievement to be “one of the most remarkable personal feats in the history of astronomy.”

The Instrument that Discovered a Planet The blink comparator used by Clyde Tombaugh in the discovery of Pluto. Tombaugh went on to scan millions of stars with this comparator during the 1930s. Image: Pretzelpaws via Wikimedia Commons

In other ways, however, not much has changed since 1930. “Clyde Tombaugh was the first to do searches as we do them today” said Brown. Like Tombaugh, Sedna’s discoverers point their telescope at regions of the sky that are in opposition to the Sun, looking for objects that exhibit retrograde motion. Just like in 1930 the modern survey moves through the skies as the Earth moves along its orbit, always pointing away from the Sun. And just like Tombaugh, his modern day successors take several images of the same spot with a time lag in between, looking for an object that has shifted its position.

Even the questions raised by the discovery of Sedna are similar to the controversies that followed the discovery of Pluto 74 years earlier: How big is Pluto/Sedna? Does it have a Moon? Is it alone, or a member of a class of objects orbiting nearby? And, most poignantly, is Pluto/Sedna a true planet?

For Brown, the parallels between the discoveries of Pluto and Sedna are inescapable. “Pluto was the first object we found in a region of the Solar System that we now know is populated by thousands of objects” he said. “Sedna is the first object to be found in the next further region.” And Brown is convinced that it will not be the last .


Some of you might recall my little web tool Blink Microscope that I wrote about last year. If you don’t, please feel free to check it out, but my focus here is on the origin of the name of the web app: it derives from a device used in astronomy that allows the user to “blink” between images of the night sky and discover minor differences. The blink microscope, also known as a blink comparator, was even involved in the discovery of Pluto.

I was therefore excited to learn that (via Alan Jacobs’s wonderful newsletter) that this technology was also used in a domain far removed from astronomy. Specifically, a similar device, known as the Hinman Collator, was used in the humanities to find minor discrepancies between different editions of texts. Imagine a scholar blinking between different editions of Charles Darwin’s On the Origin of Species and watching the changes leap out:

Arthur M. Johnson, who would take over the commercial manufacture of the collator, wrote that Hinman developed the basic design of his machine after studying something called the “astronomer's microscope.” The device to which Johnson was referring is properly known as the blink comparator and was invented in 1904 by the German instrument-maker Carl Pulfrich. The basic principle behind the blink comparator is the same as that of the Hinman. Two objects, in this case photographs of the same star field taken on different dates, are set up in the machine, superimposed, and then viewed alternately. Any difference between the images calls attention to itself by appearing, just as on the Hinman, to dance or move about. The most famous use of the comparator was made by C. W. Tombaugh, who discovered the planet Pluto with it in 1930. [quotation from here]

This is an example of the import and export of ideas. It’s the ability to take scientific concepts, technologies, or theoretical frameworks from one domain and apply them to entirely different ones. And as the world has become more specialized, this ability has become that much more important. It helps reduce reinvention of ideas, and shows that there are certain fundamentally similar insights that stretch across fields.

This import and export of ideas is also a particular skill, and one that is often undervalued in our specialized world. It requires a broad knowledge, as well as a comfort in going deep into specific areas, to learn what is known already in that domain, as well as what the holes are in that knowledge. It’s essentially an analogy-making skill, recognizing that the concept of evolution can be useful in understanding technological change, or that certain mathematical processes can help us understand the growth of the World Wide Web. This ability to make analogies and import ideas from one field and export them to another is the kind of skill that is useful in everything from scientific research to the startup and venture world, and even in writing for general audiences. As described by the subtitle of a book coauthored by Douglas Hofstadter, analogies are “the fuel and fire of thinking.” And this ability to bring ideas from one field to another is a fundamental way that we innovate.

So go out and do some import/export of knowledge.

A few things worth checking out:

Several years ago, due to a new release of Mac OS X—and what appeared to be an off-center red button—I ended up learning the term chromatic aberration.

I’ve been watching episodes of Star Trek: The Next Generation with my children. So I was delighted to discover the Star Trek Design Project: “One mildly obsessive goal: The most accurate & complete Star Trek symbol database.” It is quite the rabbit hole to go down.

This one is a couple years old but still mind-expanding: Was there a civilization on Earth before humans?

And also related to Star Trek: I enjoyed learning that the Kzinti have now been confirmed to be part of the Star Trek universe, via Star Trek: Picard. I am a huge fan of Larry Niven’s Known Space stories, where the Kzinti are one of the many species in that realm. Though it must be noted that they are not my favorite species that designation is reserved for the Pierson’s Puppeteers.

Enjoy this issue? Please feel free it to share it with a friend, and even encourage them to subscribe. Or simply let me know my preferred social network is email.

Who invented the blink comparator? - Astronomy

> Anyone that uses FITSview knows it has a great blink comparator built
> into it. Does anyone know of another software program that will
> easily blink Jpegs or BMP files?

Let me add that it seems to be a very nice program too, in all respects.

Rod Mollise
Mobile Astronomical Society
The Home of _From City Lights to Deep Space_:
Rod's Guidebook for the _Urban_ Deep Sky NUT!!

> Let me add that it seems to be a very nice program too, in all respects.

> Ouch. $249.00. Pretty steep for someone just looking for a simple
> blinker -)
> Any other "cheaper" suggestions?
> But it does seem to be a very nice piece of software.

> > Let me add that it seems to be a very nice program too, in all respects.

I just bought it a few weeks ago and I really like it. It's a better
image acquisition program than CCDOPs and it has a lot of image
processing features.

You will have to convert the images to TIFF or FITS. JPEG and
BMPs are not generally considered too useful for astrometry JPEG
is lossy, and BMPs only provide eight bits of depth.

Elsewhere in this thread, someone recommended _Guide 7.0_ and
the _Charon_ astrometry software. As the author of both programs,
I naturally think highly of them unfortunately, _Charon_ expects
either a FITS or SBIG-formatted file. Converting JPEG or BMP to
TIFF and running it through _Astrometrica_ is, in your case,
more likely to work.

Blink comparator

A blink comparator is used in astronomy comparing two photographic plates to it, celestial objects to make visible that in the lying between the recording time have changed. In contrast to the stereo comparator, the two recordings to be compared are alternately made visible to the examining astronomer in the blink comparator in quick succession (comparable to a flip book ). Thus, asteroids and comets due to their movement under the stars by jumping back and forth recognizable, and the change of light of variable stars is manifested by pulsations, caused by the different light images of the star to the two recordings.

Many such objects have been discovered in this way since the introduction of astrophotography . In 1930, Clyde Tombaugh discovered the dwarf planet Pluto while comparing two photographic plates .

With the increasing use of electronic detectors (such as the CCD ) and corresponding software for the automatic comparison of sky images and for the detection of variable stars, asteroids and other objects, the blink comparator has largely lost its importance in modern astronomy.

New Horizons

On July 14, 2015, the New Horizons probe will make the first-ever close approach of Pluto. The spacecraft should provide an unprecedented view of the double dwarf planet system.

When New Horizons launched from Florida on Jan. 19, 2006, Pluto still reigned as a full-fledged planet. It took nine and a half years for the spacecraft to make the journey to the outer edges of the solar system. Along the way, New Horizons performed flyby observations of Jupiter and its moons in 2007, when the massive planet gave the spacecraft a gravity boost.

At the end of May 2015, New Horizons reached the range where its photos were as sharp as images taken by the Hubble telescope. Throughout June, images that surpassed those captured by the space telescope were released to the public almost daily, introducing people to the dwarf planet that had once been merely a blur of pixels.

Chief among the surprises was the strong difference in coloration between Pluto and its largest moon, Charon. While Pluto is reddish brown, Charon has shown itself to be quite gray. The craft has gathered images showing the changing faces of the two, including unusual poles and puzzling spots.

On July 4, the spacecraft suffered a heart-skipping anomaly that caused the craft to enter safe mode only 10 days before its closest approach. The problem turned out to be a timing flaw in the command sequence of the craft &mdash one that should not be repeated. While some science studies were lost, the team announced that the primary objectives of the mission were not affected. New Horizons returned to normal science operations on July 7.

The close approach images that New Horizons returns to Earth will be inspiring, but they will not represent the end of the mission. The spacecraft will continue beaming data home from the flyby for months, and planetary scientists will work to understand the significance of the data for years to come.

And New Horizons will continue to cruise the outer edges of the solar system. The mission team has proposed a mission extension that would &mdash if approved and funded by NASA &mdash send the probe to fly by a second Kuiper Belt object in 2019.

Robert Burnham and his Celestial Handbook

The appeal of astronomy is both intellectual and aesthetic it combines the thrill of exploration and discovery, the fun of sight-seeing, and the sheer pleasure of firsthand acquaintance with incredibly wonderful and beautiful things…

So wrote longtime Flagstaff resident Robert Burnham, Jr., the author of one of the most prized astronomy books of our time. Burnham’s story is one of passion, persistence, and, ultimately, tragedy.

Robert Burnham, Jr. was born in Chicago on June 16, 1931. His family moved to Arizona in 1940, settling in Prescott. At an early age Robert began a lifelong pursuit of studying the universe, collecting rare coins, amassing bookshelves full of rocks and minerals, and peering at the sky through telescopes—all while reading as much as he could on each subject.

He graduated from Prescott High School in 1949 and two years later enlisted in the Air Force. After his four-year-tour finished, he returned home to Prescott and eventually took a job as a shipping clerk, though he continued his passion of studying the universe. It was at about this time that he began thinking about compiling an astronomy book like no other, one that comprehensively covered the science and mythology of all 88 constellations.

And so went Burnham’s life for several years—uninspiring job during the day, probing the depths of nature from Earth to outer space at night. And then one night in 1957 his life took a decided turn when he spotted a fuzzy patch of light through his telescope. This was a comet, and up to this day no one else had ever seen it before. He was not alone in detecting it, as two other observers independently discovered this new celestial nomad. News traveled fast and Burnham soon became a celebrity of sorts, lauded as the self-trained amateur astronomer from Prescott. None other than Senator Barry Goldwater visited Burnham and even gave the young man a family telescope that dated back to the 1800s.

Burnham Joins Lowell’s Proper Motion Survey Team

Not long after, Burnham found himself in conversation with Astronomer Henry Giclas of Lowell Observatory. Giclas had begun a program to study the movement of stars over time, a so-called proper motion survey, and hired Burnham to work on it. Soon he also moved into a cabin onsite.

Robert Burnham, Jr. and Norm Thomas at the blink comparator they used for Lowell’s Proper Motion Survey, December 1964.

Burnham would spend the next 21 years living in that same cabin at Lowell Observatory, a short stroll from telescopes he could only dream of as a kid. No longer would he have to spend many of his waking hours at a hum drum job he could now devote virtually all his waking hours to studying the universe. When not fulfilling his regular job duties of photographing the night sky and examining the resulting images, he jumped headfirst into his long-planned “Celestial Handbook”.

With the patience of Job, Burnham marched through the constellations and self-published his magnum opus in loose-leaf folders that the kids of Lowell staffers helped assemble. Eventually, with the vision of substantial royalty payments in mind, Burnham sold the rights to Dover. Little did he know that his life had reached its apex and soon would begin to spiral downward..

Life After Lowell

The proper motion survey ended in 1979 and Burnham was out of a job. After 21 years, he no longer enjoyed regular access to research telescopes, no longer had a home, no longer had a regular income. To many people this would have been a challenge but one they could conquer. To Burnham, this was almost a death sentence. As eloquent as Burnham was on paper, he was equally awkward in person. Exceptionally introverted—former Lowell Observatory Director Bob Millis calls Burnham the most shy person he ever met—Burnham was not one to go out into the world and start over. Without the regularity of his beloved work and the stability of his adopted lifetsyle–as well as an apparent psychosis that would plague him for the rest of his life–he was lost.

Burnham lived with his sister for a short time and then disappeared, with neither family nor friends knowing his whereabouts. A few years later, the son of one of Burnham’s closest Lowell colleagues was walking through Balboa Park in San Diego when he noticed a skinny, bearded man. As he drew near, he realized the man was Burnham. He learned that Burnham lived in bleak housing nearby, having never seen the riches he expected from the handbook royalties and making a minimal living by selling paintings of cats in the park.

In 1993, at the age of 61 and after suffering from a heart attack and other health maladies, Burnham died. His remains went to Fort Rosecrans National Cemetery’s columbarium in San Diego. Burnham was a loner to the end: his name was misspelled on his grave marker and his family didn’t even find out he died until two years later.

Burnham’s Celestial Handbook is a staple in the library of astronomy enthusiasts around the world.

Celebrating Robert Burnham, Jr.

While Burnham’s tragic life ended in obscurity, his beloved handbook lives on and is a staple in the library of thousands of astronomers, professional and amateur alike. Burnham chronicler Tony Ortega has called Burnham’s 2138-page handbook a real-life Hitchhiker’s Guide – “part travel guide, part history text, part encyclopedia, it’s like a handheld natural-history museum of the universe.”

In recent years, efforts have been made to honor Robert Burnham. Amateur astronomers in Phoenix led an effort to create a plaque honoring Burnham, and Lowell Observatory is now developing a new display highlighting his life and work.

Next week, as part of National Astronomy Day, Lowell Observatory is hosting a virtual discussion about the triumph and tragedy of Burnham. Ortega, Burnham’s niece Donna Courtney, and renowned sky expert Brian Skiff of Lowell will participate and take questions from the virtual audience. The event begins at 6:30 pm on September 26, via Lowell Observatory’s YouTube page.

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Secrets of Lowell: The Slipher Building

Due north of the Steele Visitor Center, a venerable stone building rises three stories above the ground and one story below. Perhaps its most distinctive feature is the domed structure at its center, and the set of large (yet almost whimsically inviting) wooden doors that guard the treasures inside. On either side of the dome lie the offices of some of Lowell’s most vital and tenured staff members including astronomers, researchers, historians, and Lowell’s current director.

The construction of the Slipher Building’s library, known today as the Rotunda Museum | Lowell Observatory Archives

Built in 1916, the Slipher Building was created to meet a growing need for office and darkroom space. The land that the Slipher Building occupies today is near where the Baronial Mansion once stood, a dwelling that was home to Percival Lowell, his wife Constance, his assistant Wrexie Leonard, his personal secretary, and two household servants. It was the last building to be constructed on Mars Hill during observatory founder Percival Lowell’s lifetime, completed shortly before his death in November of 1916. A second story and extensive attic were added in 1923, after leaks in the original single-story building’s temporary flat roof caused significant damage to the interior.

The Slipher Building’s expansive basement houses more offices and the photographic plate vault that stores the historic Pluto Discovery Plates, along with other vital images taken with the 13” astrograph used to discover Pluto. Pluto discoverer Clyde Tombaugh lived and worked in the Slipher Building when he discovered the fabled ninth planet on February 18, 1930. His apartment was located on the second floor, and is still used today as lodging for special observatory guests. Tombaugh’s office was located on the first floor, right next door to the room that housed the blink comparator.

The interior stairs of the Slipher Building library leading up to another area for books. These stairs can be seen today inside the Rotunda Museum | Lowell Observatory Archives

The interior of the Slipher Building’s dome, now called the Rotunda Museum, still contains a pair of spiral staircases that lead to a small mezzanine lined with bookshelves. These shelves hold the personal library of Dr. Carl O. Lampland, a former astronomer. During his time at Lowell, Lampland designed cameras for telescopes, measured temperatures of the planets in our solar system, and captured more than 10,000 images of planets, comets, variable stars, nebulae, and star clusters in our galaxy. Suspended from the ceiling of the dome is the Saturn Lamp, a stained-glass light fixture crafted by the Los Angeles Light Company in 1918. Other noteworthy items displayed in the Rotunda Museum are Percival Lowell’s first telescope, the blink comparator Clyde Tombaugh used to discover Pluto, and an interactive projector globe.

The Slipher Building continues to be a nexus of discovery at Lowell even today. Astronomer Nick Moskovitz and his team are currently conducting research from the building’s roof, scanning the sky for meteors each night using a LO-CAMS (Lowell Observatory Cameras for All-Sky Meteor Surveillance) station. The Slipher has also been the site of some particularly special events in the lives of Lowell staff: observatory historian Kevin Schindler’s wedding was held in the Rotunda Museum!

The Instrument that Discovered a Planet

The Instrument that Discovered a Planet The blink comparator used by Clyde Tombaugh in the discovery of Pluto. Tombaugh went on to scan millions of stars with this comparator during the 1930s. Pretzelpaws via Wikimedia Commons

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. For uses not allowed by that license, contact us to request publication permission from the copyright holder.

Original image data dated on or about 10 August 2005

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