<p>A while ago I saw a report on TV, where an astronomer described a device that was used for detecting movement of stellar objects (mainly asteroids, I think) before the age of computers. In order to detect such a movement, two photos of the region of interest were made, through a telescope, with a certain delay between these photos. </p>

<p>Afterwards, the photos have been placed into that device. The device had some sort of "peephole" through which one could see one of the photos, and some sort of lever/switch to quickly toggle between the photos - either by flipping them, or by tilting a mirror to show either of the photos. </p>

<p>Objects that had moved between the photos (relative to the other, "fixed" objects) could thus quickly and easily be identified with the naked eye, because they appeared as dots jumping forth and back when toggling between the photos.</p>

<p>Does anybody know the name of this device, or a more detailed technical description?</p>

CC BY-SA 3.0
2017-12-19T01:42:30.117Z
A [blink comparator](https://en.wikipedia.org/wiki/Blink_comparator).
Mick
CC BY-SA 3.0
2017-12-19T01:46:35.557Z
@Mick Thanks, that basically could be an answer. (And it's somewhat embarassing that I didn't find it myself - all the keywords have been there, but google only led me to completely unrelated sites... :-/ )
Marco13
CC BY-SA 3.0
2017-12-19T01:49:18.123Z
It's a bit short for an answer. Maybe someone else can expand on it.
Mick
CC BY-SA 3.0
2017-12-19T09:54:11.177Z
@Mick see several answers to [Who invented the blink comparator?](https://astronomy.stackexchange.com/q/11242/7982)
uhoh
CC BY-SA 3.0
2017-12-19T10:02:26.907Z
@uhoh Thanks. I flagged it as a duplicate. It's a bit of a cop-out, I know, but anyone who comes looking will be directed to useful information.
Mick
CC BY-SA 3.0
2017-12-19T14:17:28.807Z
@Mick I think in this case it's the right thing to do. I don't see anything in the question that isn't answered there. If there's a need for even further detail, the OP can edit the question or even ask a new one.
uhoh
CC BY-SA 3.0
2017-12-19T20:50:18.793Z
Indeed, the linked answer contains many more details - if and only if you know that this thingy is called "blink comparator" in the first place ;-)
Marco13
<telescope><observational-astronomy><movement>
What is the name of a device for detecting moving objects?
Marco13
# What is the name of a device for detecting moving objects?

(Asked by: username_0 on 2017-12-19)

A while ago I saw a report on TV, where an astronomer described a device that was used for detecting movement of stellar objects (mainly asteroids, I think) before the age of computers. In order to detect such a movement, two photos of the region of interest were made, through a telescope, with a certain delay between these photos.

Afterwards, the photos have been placed into that device. The device had some sort of "peephole" through which one could see one of the photos, and some sort of lever/switch to quickly toggle between the photos - either by flipping them, or by tilting a mirror to show either of the photos.

Objects that had moved between the photos (relative to the other, "fixed" objects) could thus quickly and easily be identified with the naked eye, because they appeared as dots jumping forth and back when toggling between the photos.

Does anybody know the name of this device, or a more detailed technical description?

**Tags:** telescope, observational-astronomy, movement
> **Comments:**
> **username_1**: A [blink comparator](https://en.wikipedia.org/wiki/Blink_comparator).  
> **username_0**: @Mick Thanks, that basically could be an answer. (And it's somewhat embarassing that I didn't find it myself - all the keywords have been there, but google only led me to completely unrelated sites... :-/ )  
> **username_1**: It's a bit short for an answer. Maybe someone else can expand on it.  
> **username_2**: @Mick see several answers to [Who invented the blink comparator?](https://astronomy.stackexchange.com/q/11242/7982)  
> **username_1**: @uhoh Thanks. I flagged it as a duplicate. It's a bit of a cop-out, I know, but anyone who comes looking will be directed to useful information.  
> **username_2**: @Mick I think in this case it's the right thing to do. I don't see anything in the question that isn't answered there. If there's a need for even further detail, the OP can edit the question or even ask a new one.  
> **username_0**: Indeed, the linked answer contains many more details - if and only if you know that this thingy is called "blink comparator" in the first place ;-)  

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