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"Women computers", Astrophotography's history, and "Plate Solving"

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#1 t_image

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Posted 12 December 2018 - 04:13 AM

So,

often I see conversation about "plate solving" in AP forums

in reference to the an astrophotographer's acquisition phase of utilizing software to:

  • take an image
  • figure out where the image is located in reference to the universe
  • and automatically point the mount/sensor/optics towards where the user is intending to point.....

For precision's sake:
What I've been able to gather:

  1.  the term is much older than any software program.
  2.  it specifically refers to the process of coming up with a solution to the question:("where on a map of stars does the image refer?") [and maybe functionally annotate it for helpful current/later research]......
  3.  the "plate" is an old reference to the use of photographic plates in astrophotography that preceded the use of photographic film.*
  4.  In the olden days of plates the "solving" was NOT done with electronic computers and software.

--in fact, a short bit of research into "Pickering's Women" will point (pun intended) one towards stories of how women have significantly contributed to astronomy and astrophysics in the past.  https://siarchives.s...pickering-women

*also see:

https://www.pbs.org/...tronomy-plates/

 

IMO the short speak of "plate solving" to refer to using a software program for the result of accurately point a telescope mount/OTA,

instead of the term used to specifically refer to the complex operation of figuring out the solution to the image alone,

contributes to a loss of an important part of astrophotography's history....

 

It may be a small distinction, but sometimes small distinctions are important in the area of astronomy (what do we call Pluto?).....

 

I blame the software developers that are the major culprits, as the action should be labeled "Capture,Solve, and Point."

 

All are free to use the "new tech term" colloquially to signify the entire process of capture/solve/point as most amateur astrophotographers are only using the solving process for such an outcome,

[although many stacking software programs do it for the purpose of precise alignment of each image in the stack and not to point mount/scope]

but for the sake of the ancients,

at least remember that it is short speak!

smile.gif

**note the term "astrometric solving" is another current term to refer to the process (plate solving) for the immediate result of precise measurements (of where) given the image....

 

If anyone is able to give further historical light on the matter I'd be interested.....

 

Cheers!

plate solving in earlier.jpg

source image at:

https://en.wikipedia...d_computers.jpg



#2 freestar8n

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Posted 12 December 2018 - 04:39 AM

I use the term "plate solving" but it has nothing to do with pointing the telescope.  It is specific to using the pattern of stars in the image to determine the location and orientation of the image in the sky.

 

People use plate solves to align and orient the telescope - but that usage is no different from the original.  It is just one part of an overall system.

 

So - I use plate solving to point the telescope at specific locations in the sky.  I also use servo motors, software, etc.  But plate solving does not mean "pointing the telescope" any more than "servo motor" does.

 

The fact that we use the term "plate" does keep it in the historical (glass emulsion) context - and causes no confusion either.  So if you want to maintain a tie to the past - I think it's there.

 

I have written my own plate solver and I use it to point my telescope accurately.  This stuff has become common for amateur usage only in recent years - and it has been very beneficial.

 

Frank


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#3 beggarly

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Posted 12 December 2018 - 06:41 AM

... further historical light on the matter...
read about Photometry and Astrometry.
 
 
 


#4 ks__observer

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Posted 12 December 2018 - 07:22 AM

Great historical info.

I would favor keeping the historical ref in the naming the process.

I think it is a nice reminder of how far we have come.

Even my AP capture software,APT, still uses the term "bulb."

"Bug" for computer glitches is another that comes to mind.


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#5 APshooter

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Posted 12 December 2018 - 12:25 PM

The new Cosmos series (no longer on Youtube) had a great episode about Pickering's Women.



#6 John Miele

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Posted 12 December 2018 - 01:29 PM

So,

often I see conversation about "plate solving" in AP forums

in reference to the an astrophotographer's acquisition phase of utilizing software to:

  • take an image
  • figure out where the image is located in reference to the universe
  • and automatically point the mount/sensor/optics towards where the user is intending to point.....

For precision's sake:
What I've been able to gather:

  1.  the term is much older than any software program.
  2.  it specifically refers to the process of coming up with a solution to the question:("where on a map of stars does the image refer?") [and maybe functionally annotate it for helpful current/later research]......
  3.  the "plate" is an old reference to the use of photographic plates in astrophotography that preceded the use of photographic film.*
  4.  In the olden days of plates the "solving" was NOT done with electronic computers and software.

--in fact, a short bit of research into "Pickering's Women" will point (pun intended) one towards stories of how women have significantly contributed to astronomy and astrophysics in the past.  https://siarchives.s...pickering-women

*also see:

https://www.pbs.org/...tronomy-plates/

 

IMO the short speak of "plate solving" to refer to using a software program for the result of accurately point a telescope mount/OTA,

instead of the term used to specifically refer to the complex operation of figuring out the solution to the image alone,

contributes to a loss of an important part of astrophotography's history....

 

It may be a small distinction, but sometimes small distinctions are important in the area of astronomy (what do we call Pluto?).....

 

I blame the software developers that are the major culprits, as the action should be labeled "Capture,Solve, and Point."

 

All are free to use the "new tech term" colloquially to signify the entire process of capture/solve/point as most amateur astrophotographers are only using the solving process for such an outcome,

[although many stacking software programs do it for the purpose of precise alignment of each image in the stack and not to point mount/scope]

but for the sake of the ancients,

at least remember that it is short speak!

smile.gif

**note the term "astrometric solving" is another current term to refer to the process (plate solving) for the immediate result of precise measurements (of where) given the image....

 

If anyone is able to give further historical light on the matter I'd be interested.....

 

Cheers!

attachicon.gif plate solving in earlier.jpg

source image at:

https://en.wikipedia...d_computers.jpg

I thought these women were measuring variable stars (comparative brightness?). Not really "plate solving". But I could easily be wrong...John


Edited by John Miele, 12 December 2018 - 01:31 PM.

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#7 freestar8n

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Posted 13 December 2018 - 02:36 AM

I thought these women were measuring variable stars (comparative brightness?). Not really "plate solving". But I could easily be wrong...John

There are several levels to all this.  One is just to have an image, or plate, and know the ID of each star because you know where it is aimed - and you have an atlas of stars in the area.  If you are looking for variable stars or something - you don't need a "plate solve".  You can just be handed a plate and knowing it's approximate ra/dec in the center - and plate scale - you can know what patch of sky it is - and then visually do the star matching to make the measurements and assign them to the correct star ID.  I assume that is what is happening in the images above - and I don't think it's plate solving.

 

Plate solving would be more for mapping - and involve knowing the exact scale, center, and orientation of the image - so that *unknown* stars could be measured and assigned ra/dec values.  And back then I assume it would involve knowing the approx coordinates of the image - and the scale - and using known stars to figure out the plate orientation exactly.

 

Much more recently, with space missions and electronic imaging, there became a need to look at a pattern of stars and ask, "where the heck am I?" - because with a satellite in space the orientation isn't known a priori.  And the key to that is a form of star pattern recognition - that looks at patterns of stars and maps them to known patterns of stars.  And this was done early on by looking at triangle patterns of stars and creating a "hash" for them that was independent of scale, orientation, and mirror inversion.

 

More recently methods have become popular to use patterns of 4 stars in quads.  And if done properly it allows a completely blind solve - where given an image anywhere in the sky - at any scale and orientation - you can identify the patterns of stars in the image - and then as a secondary result - provide a "plate solve" for the image.

 

That's what's happening when people center a telescope accurately based on "plate solves" - either using pattern recognition given hints of location and scale - or completely blind not knowing anything.  But all that's really needed is the center RA/Dec value - which is only part of what a plate solve provides.  And the overall process of centering based on that RA/Dec value requires much more than what's involved in a plate solve.  It requires measuring the current RA/Dec, then making adjustments and trying again - etc.

 

Frank


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#8 t_image

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Posted 13 December 2018 - 09:56 AM

I thought these women were measuring variable stars (comparative brightness?). Not really "plate solving". But I could easily be wrong...John

Great question! As Frank points out plate solving is a particular foundational step.

This link describes a few named ladies at Harvard that did the observational/number crunching labors for a number of advancements in astronomy/astrophysics besides variable star identification/measurement.

Note Annie Jumper Cannon developed the Harvard Spectral Classification system, a result of efforts of other Harvard "Computers" and Pickering's Objective-Prism method, which he developed "to photograph the spectra of multiple stars simultaneously by putting a large prism in front of the photographic plate."

https://en.wikipedia...rvard_Computers

https://en.wikipedia...arles_Pickering

 

Enjoy this entertaining short video summary of Cannon's work from a young lady:

https://www.youtube....h?v=seyJFtW6z10

 

There are several levels to all this....

Quite helpful Frank.

Of course plate solving is just an initial step, not that the forerunner's of Astrophotographer stopped there.
Also, their goals were more of scientific discovery/evaluation than the objectives of a pretty picture that many amateurs pursue.

This leads to the realm of photogrammetry (making measurements from photos). And hence the creation of the term "astrometry."
Somewhere in the process of measurements for each image, there needs to be a correct identity found in order to catalog/classify, etc...

-----as this link with the associated photograph describes:

"The daily work was largely clerical: some women would reduce the photographs, taking into account things like atmospheric refraction, in order to render the image as clear and unadulterated as possible. Others would classify the stars through comparing the photographs to known catalogs. Others cataloged the photographs themselves, making careful notes of each image’s date of exposure and the region of the sky. The notes were then meticulously copied into tables, which included the star’s location in the sky and its magnitude."

https://www.smithson...espect-9287444/

 

One is just to have an image, or plate, and know the ID of each star because you know where it is aimed - and you have an atlas of stars in the area.  If you are looking for variable stars or something - you don't need a "plate solve".  You can just be handed a plate and knowing it's approximate ra/dec in the center - and plate scale - you can know what patch of sky it is - and then visually do the star matching to make the measurements and assign them to the correct star ID.  I assume that is what is happening in the images above - and I don't think it's plate solving.

To know a star's location necessarily implies it was gathered from measurements in the image.

I have seen elsewhere the term "plate solve" in reference to particular objects in an image : i.e. "this object is identified as xyz as a result of the plate solve."

There is a distinction between a "blind plate solve" and one where most conditions might be known, but there is an unknown, yes?

 

Plate solving would be more for mapping - and involve knowing the exact scale, center, and orientation of the image - so that *unknown* stars could be measured and assigned ra/dec values.  And back then I assume it would involve knowing the approx coordinates of the image - and the scale - and using known stars to figure out the plate orientation exactly.

Regardless, the process of astrometric solving was being done independent of the task (noticing variable stars, determining a stellar object's spectrum, etc.)...

Of course my posted MEME took liberty to illustrate my point about the term plate solving, regardless of whether the photo shows the ladies immediately doing such....

 

And of course some type of "plate solving" seems to have happened back then,

since the term "plate" was time specific......

 

Much more recently, with space missions and electronic imaging, there became a need to look at a pattern of stars and ask, "where the heck am I?" - because with a satellite in space the orientation isn't known a priori.  And the key to that is a form of star pattern recognition - that looks at patterns of stars and maps them to known patterns of stars.  And this was done early on by looking at triangle patterns of stars and creating a "hash" for them that was independent of scale, orientation, and mirror inversion.

It is interesting that you mention the use of star trackers on spacecraft and the process where they determine the craft's attitude. Funny enough, the term "plate solving" isn't commonly used at all in this arena. At most "solve" may be used.

I believe initially spacecraft used measurements from Sun detectors, measuring the Earth's magnetic field, and locking on and tracking available stars until they disappeared to gather data that was then sent to a ground station via telemetry and then the craft's position could be calculated with ground systems and then craft adjustments then could be relayed back to the craft.....

Of course as it became possible to add better computational electronics on-board, and with the innovation of better star detection capabilities in a small star tracker,

astrometric solving in order to determine attitude could be done onboard, quickly and adjustments could be made rapidly as well making things better in so many aspects!

 

More recently methods have become popular to use patterns of 4 stars in quads.  And if done properly it allows a completely blind solve - where given an image anywhere in the sky - at any scale and orientation - you can identify the patterns of stars in the image - and then as a secondary result - provide a "plate solve" for the image.

 

That's what's happening when people center a telescope accurately based on "plate solves" - either using pattern recognition given hints of location and scale - or completely blind not knowing anything.  But all that's really needed is the center RA/Dec value - which is only part of what a plate solve provides.  And the overall process of centering based on that RA/Dec value requires much more than what's involved in a plate solve.  It requires measuring the current RA/Dec, then making adjustments and trying again - etc.

 

Frank

Thanks for sharing an overview of the computational development of algorithms to identify a starfield!


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