<p>I don't know if the loss of an eye (mentioned in <a href="https://astronomy.stackexchange.com/a/11254/7982">this answer</a>) is related, but there is a one-eyed embodiment described in the 1909 patent <a href="https://www.google.com/patents/US941812" rel="nofollow noreferrer"> US941812, Telemeter for two successive observations</a>.</p>

<blockquote>
  <p>"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."</p>
</blockquote>

<p><a href="https://i.sstatic.net/WG9md.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/WG9md.png" alt="enter image description here"></a></p>

<p>Thus it seems the comment at the bottom of the the first page in <a href="http://www.math.harvard.edu/~knill/history/wolf/bea_proofs_wolf.pdf" rel="nofollow noreferrer">this article</a> might not be 100% correct. I don't know the date, but the one-eyed blink comparator in Wikipedia looks pretty darn old!</p>

<blockquote>
  <p>"Tragically, Pulfrich lost one eye in 1906,
  preventing him from using the stereographic tool from then on." </p>
</blockquote>

<p>The full quote can be found in the <a href="https://astronomy.stackexchange.com/a/11254/7982">other answer</a>.</p>

<p><a href="https://i.sstatic.net/oM7Ie.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/oM7Ie.jpg" alt="enter image description here"></a></p>

<p><strong>above:</strong> "English: Blink comparator in the Meridian hall of the Helsinki observatory. Made by Carl Zeiss in early 20th century." from <a href="https://commons.wikimedia.org/wiki/File:Blink_comparator_1.JPG" rel="nofollow noreferrer">here</a></p>

<p><a href="https://i.sstatic.net/14U0c.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/14U0c.jpg" alt="enter image description here"></a></p>

<p><strong>above:</strong> from <a href="https://airandspace.si.edu/stories/editorial/finding-pluto-blink-comparator" rel="nofollow noreferrer">Finding Pluto with a Blink Comparator</a></p>

CC BY-SA 3.0
2017-01-28T05:32:17.903Z
2017-01-28T05:51:23.007Z
2017-04-13T12:59:07.017Z
uhoh
<p>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</p>

CC BY-SA 3.0
2017-01-28T14:15:00.917Z
Thanks for your answer. However, I'm not sure what it adds to the existing answer from July '15.
James K
CC BY-SA 3.0
2017-01-28T02:25:49.960Z
2017-01-28T02:25:49.960Z
Ruth Mendoza
<p>It would appear to have been developed by <a href="http://www.city-of-light.com/en/topics/topics-detailpage/?tx_ttnews%5Btt_news%5D=275&amp;cHash=2e1a29de74aaa837a979293e8e926538">Carl Pulfrich working for Zeiss</a> in 1904.</p>

<p>Alternatively <a href="http://www.math.harvard.edu/~knill/history/wolf/bea_proofs_wolf.pdf">Max Wolf</a> in 1900 again working with the Zeiss company.</p>

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

<blockquote>
  <p>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.</p>
</blockquote>

CC BY-SA 3.0
2017-01-28T05:20:01.790Z
Maybe "tragically" is a bit of an overstatement as far as loss of blink comparison viewing. It sounds like Pulfrich could have invented a rotating mirror that could direct alternating paths to a single eyepiece, or even a small version of the [PROBLECOM](https://books.google.com.tw/books?id=khtT0QAXI9QC&lpg=PA142&ots=w1ATiJWz9D&dq=PROBLICOM%20%20projection%20blink%20comparator&pg=PA142#v=onepage&q=PROBLICOM%20%20projection%20blink%20comparator&f=false) projecting on to ground glass if he really wanted to look for variable or moving objects in plates.  https://i.sstatic.net/jUbrb.png
uhoh
CC BY-SA 3.0
2017-01-28T05:33:47.220Z
Wait - it seems he did! [US941812](https://www.google.com/patents/US941812) more detail in [this answer](http://astronomy.stackexchange.com/a/19874/7982).
uhoh
CC BY-SA 3.0
2015-07-11T14:30:34.547Z
2015-07-11T14:59:56.753Z
2015-07-11T14:59:56.753Z
Conrad Turner
<p>The Wikipedia page for the <a href="http://en.wikipedia.org/wiki/Blink_comparator" rel="nofollow">blink comparator</a> fails to mention who invented it. Many other pages extol the importance of the device, but we cannot find any mention of an inventor.</p>

<p>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.</p>

<telescope><history>
Who invented the blink comparator?
Happy Phantom
# Who invented the blink comparator?

(Asked by: username_0 on 2015-07-10)

The Wikipedia page for the [blink comparator](http://en.wikipedia.org/wiki/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.

**Tags:** telescope, history


---

## 3 answers

### Answer by username_4 on 2015-07-11. Score: 5 | Accepted answer

It would appear to have been developed by [Carl Pulfrich working for Zeiss](http://www.city-of-light.com/en/topics/topics-detailpage/?tx_ttnews%5Btt_news%5D=275&cHash=2e1a29de74aaa837a979293e8e926538) in 1904.

Alternatively [Max Wolf](http://www.math.harvard.edu/~knill/history/wolf/bea_proofs_wolf.pdf) 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.

> **Comments:**
> **username_1**: Maybe "tragically" is a bit of an overstatement as far as loss of blink comparison viewing. It sounds like Pulfrich could have invented a rotating mirror that could direct alternating paths to a single eyepiece, or even a small version of the [PROBLECOM](https://books.google.com.tw/books?id=khtT0QAXI9QC&lpg=PA142&ots=w1ATiJWz9D&dq=PROBLICOM%20%20projection%20blink%20comparator&pg=PA142#v=onepage&q=PROBLICOM%20%20projection%20blink%20comparator&f=false) projecting on to ground glass if he really wanted to look for variable or moving objects in plates.  https://i.sstatic.net/jUbrb.png  
> **username_1**: Wait - it seems he did! [US941812](https://www.google.com/patents/US941812) more detail in [this answer](http://astronomy.stackexchange.com/a/19874/7982).  

---

### Answer by username_1 on 2017-01-28. Score: 2

I don't know if the loss of an eye (mentioned in [this answer](https://astronomy.stackexchange.com/a/11254/7982)) is related, but there is a one-eyed embodiment described in the 1909 patent  [US941812, Telemeter for two successive observations](https://www.google.com/patents/US941812).

> "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."

[![enter image description here](https://i.sstatic.net/WG9md.png)](https://i.sstatic.net/WG9md.png)

Thus it seems the comment at the bottom of the the first page in [this article](http://www.math.harvard.edu/~knill/history/wolf/bea_proofs_wolf.pdf) 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](https://astronomy.stackexchange.com/a/11254/7982).

[![enter image description here](https://i.sstatic.net/oM7Ie.jpg)](https://i.sstatic.net/oM7Ie.jpg)

**above:** "English: Blink comparator in the Meridian hall of the Helsinki observatory. Made by Carl Zeiss in early 20th century." from [here](https://commons.wikimedia.org/wiki/File:Blink_comparator_1.JPG)

[![enter image description here](https://i.sstatic.net/14U0c.jpg)](https://i.sstatic.net/14U0c.jpg)

**above:** from [Finding Pluto with a Blink Comparator](https://airandspace.si.edu/stories/editorial/finding-pluto-blink-comparator)


---

### Answer by username_2 on 2017-01-28. Score: 1

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

> **Comments:**
> **username_3**: Thanks for your answer. However, I'm not sure what it adds to the existing answer from July '15.  

---

