Starship Asterisk*

a 'photograph' is an image recorded on a light-sensitive film or plate

The word, coined by Hershel, comes from the Greek Phos and Graphis, which reduces basically to "drawing with light" - if you research the terms you can see how it is derived.

Thus a "photograph" is an image made by light upon a light sensitive surface. Photographic film/plates represent just one technology of light sensitive surface. A CCD or CMOS chip is equally a light sensitive surface. By masking a leaf on a plant you can make "photographs" using the reaction of the light sensitive pigments in the leaves as such a surface - these are, by literal definition, also photographs, (although other media often require shorter exposure times).

As the term 'photography' is used by amateur astronomers, there is some, shall we say, wobbliness ... at least if Sky&Telescope is a reliable guide to usage.

For example, under HOW TO there is a section called astrophotography: while '(astro)photographer' seems unique and consistent (the person doing the photography/imaging), the process is called 'imaging' more often than 'photography' (ditto the verbs, 'to image/imaging' vs 'to photograph/photographing'). For the end result - 'image' or 'photograph' - usage is quite a mixture! However, when a camera is involved, 'photograph' is most often used, whether it's 'film or digital'; but when it's 'an imaging system', then it seems 'photograph' is not what the astrophotographer ends up with.

Turning to the professional astronomy community, a search of papers (etc) in ADS with the word 'photography' in their titles, in 2007 and 2008, returned 118 hits. Many of these were false positives ('photo-polarimetry' for example), and some purely social (e.g. "Conference photograph"). Many uses were clearly limited to plates (or film) (e.g. "A Census of North American Astronomical Photographic Plates"), some agnostic (e.g. "Reduction of photographic observations of asteroids to the reference frame of a single catalog"), and a few with the broad definition adrianxw gave (e.g. "Book review: Introduction to Webcam Photography").

However, within the same timeframe, "imaging" returned 2419 hits, with fewer false positives (so it seems to me). Of course, some 'imaging' involves wavebands other than 'light' (UV, visible, near-IR) - e.g. "High-Resolution X-Ray Imaging of the Center of IC 342" - but perhaps most indicative of the trend towards 'imaging' for the meaning in adrianxw's post are these two: "Visualising Astronomy: The Astronomical Image, Part Two" and "Blind Date: Using Proper Motions to Determine the Ages of Historical Images" ... in the latter, the 'historical images' are photographic plates!

adrianxw wrote:This galaxy look deformed to me. The centre section seems tilted relative to the outer lying blue spiral arms.

[...]

It could be some kind of optical illusion.

To readers who are not professional astronomers: what sorts of things do you think one could do to go about finding out whether NGC 7331 is, in fact, 'deformed' in some way, in its centre section?

In particular, how could one demonstrate - objectively - that there is some deformation, and, if so, measure the degree of deformation in some quantitative fashion?

Sputnick wrote:I guess then, Psyched, you'd enjoy hearing "the music of the spheres" spoken of in the bible.

I don't know about the bible, haven't listened to it. Can't seem to get it in my CD player. However, Music of the Spheres by Mike Oldfield is quite good. And then there is Kepler's Music of the Spheres.

Kepler's, First Law states that the planets move in ellipses and that the Sun is not at the exact centre of their orbits. Each planet moves between a 'perihelion' point nearest the Sun and an 'aphelion' point furthest away. The Second Law states that the planets move faster at perihelion than at aphelion. Kepler measured their angular velocities at these extremes (i.e. how far they travel in 24 hours in minutes and seconds of arc as viewed from the Sun) and expressed this ratio as a musical interval. ... Kepler found that the angular velocities of all the planets closely correspond to musical intervals. When he compared the extremes for combined pairs of planets the results were even more marvellous, yielding the intervals of a complete scale. Thus, the ratio between Jupiter's maximum and Mars' minimum speed corresponds, to a minor third; the interval between Earth and Venus to a minor sixth. Rather than the fixed-tone planetary scales of earlier schemes, Kepler's measurements revealed ever-changing polyphonic chords and harmonies as the planets move between perihelion and aphelion. Furthermore, he had shifted the focus of celestial harmony from the Earth to the Sun: "Henceforth it is no longer a harmony made for the benefit of our planet, but the song which the cosmos sings to its lord and centre, the Solar Logos".

Bystander and Nereid - "Fascinating" - thanks.

When I was about 12 years of age I tuned my old time radio between stations and listened to pulses, hums, lovely static .. fantastically musical and reminding me of Oldfield, Pink Floyd, Moody Blues at later time. When young and listening to the signals between stations I lived out in the country distant from large electrical sources, and I have always wondered how much of that stuff was from the stars? Do radio astronomers tune in and 'listen'?

I just wish a photograph was a photograph instead of an artist's conception, which this one obviously is.

It's easy to veer off from discussing things to discussing names of things. What does it matter if the thing in question is called a photograph or a simulacrumgraph or something else? Well, I suppose it can matter when names of things are applied precisely. One would want to distinguish between a photograph and a painting because they were produced differently. These days the term "image" is used more and more frequently, I guess because there are more different ways of producing images than there were in the past. "Image" is a broader term than photograph or painting, for example, and a less precise one in denoting the means of creating the image. "Image" seems to refer more to the impression on the retina of the observer than to the means of creation of the image.

A rose by any other name would smell as sweet.

bystander wrote:

emc wrote:http://en.wikipedia.org/wiki/Barred_spi ... y#The_bars

So the prominent bar tell us that the distant "alligator" galaxy is younger than the one in the foreground?

Alternatively, since the foreground galaxy is closer, it must be younger. To add to the confusion, the next paragraph in the wiki article you quoted begins with:

Recent studies have confirmed the idea that bars are a sign of galaxies reaching full maturity as the "formative years" end.

Anyway, what I originally thought could be a dwarf is obviously an even more distant spiral. However, there are two smudges to the top left of NGC 7331 (one left of your "alligator", the other below that) that could be companions, as well as what looks like could be star streams.

Thanks bystander... always helpful!

I wondered about the distant/age thing but figured that galaxies must be different ages??? So I thought a 10X distant one could still be younger.

vperis wrote:Hello all,

after reading this thread, I think I must write a short note here about the image.

Sputnick, this photo is as real as your face. The data is real: the telescope has been acquiring real photons during several hours. And I apply processes that can be applied to daylight photos. The only difference from daylight photography is that, being documental photography, if you want to show all the features of the objects being photographed, you must push up a bit more the processes you apply.

Said this, this photograh is NOT a painting. Please, be sure you are able to make a statement before making it.

Best regards,
Vicent.

Just extending my welcome and letting you know your forum contributions are well received also. It is a pleasure and it adds greater dimension to have an APOD author speak here. 8) Thanks!

psyched wrote:

I just wish a photograph was a photograph instead of an artist's conception, which this one obviously is.

It's easy to veer off from discussing things to discussing names of things. What does it matter if the thing in question is called a photograph or a simulacrumgraph or something else? Well, I suppose it can matter when names of things are applied precisely. One would want to distinguish between a photograph and a painting because they were produced differently. These days the term "image" is used more and more frequently, I guess because there are more different ways of producing images than there were in the past. "Image" is a broader term than photograph or painting, for example, and a less precise one in denoting the means of creating the image. "Image" seems to refer more to the impression on the retina of the observer than to the means of creation of the image.

A rose by any other name would smell as sweet.

Our senses don't normally see in the infrared or UV, and if they did perhaps the image in question would look to us somewhat like it appears on apod .. and art of course can imitate reality .. but I prefer to see things as they are to our normal senses. If we begin to alter colours, what stops us from altering squares to circles. If someone wants to present an image on apod which has been digitally altered, then they should at least present it as such. Perhaps your 'rose' quotation is a good example, because with humans altering roses the sweet scent has gone out of most of them.

Nereid wrote:

adrianxw wrote:This galaxy look deformed to me. The centre section seems tilted relative to the outer lying blue spiral arms.

[...]

It could be some kind of optical illusion.

To readers who are not professional astronomers: what sorts of things do you think one could do to go about finding out whether NGC 7331 is, in fact, 'deformed' in some way, in its centre section?

In particular, how could one demonstrate - objectively - that there is some deformation, and, if so, measure the degree of deformation in some quantitative fashion?

It would be nice to be able to do a "flyby" on my way home for supper this evening... but that is not possible ... my tank only holds 14 gallons.

Could the deformation or illusion be demonstrated by measuring each star's position and creating a 3D computer model?

Sputnick wrote:

psyched wrote:

I just wish a photograph was a photograph instead of an artist's conception, which this one obviously is.

It's easy to veer off from discussing things to discussing names of things. What does it matter if the thing in question is called a photograph or a simulacrumgraph or something else? Well, I suppose it can matter when names of things are applied precisely. One would want to distinguish between a photograph and a painting because they were produced differently. These days the term "image" is used more and more frequently, I guess because there are more different ways of producing images than there were in the past. "Image" is a broader term than photograph or painting, for example, and a less precise one in denoting the means of creating the image. "Image" seems to refer more to the impression on the retina of the observer than to the means of creation of the image.

A rose by any other name would smell as sweet.

Our senses don't normally see in the infrared or UV, and if they did perhaps the image in question would look to us somewhat like it appears on apod .. and art of course can imitate reality .. but I prefer to see things as they are to our normal senses. If we begin to alter colours, what stops us from altering squares to circles. If someone wants to present an image on apod which has been digitally altered, then they should at least present it as such. Perhaps your 'rose' quotation is a good example, because with humans altering roses the sweet scent has gone out of most of them.

Hi Sputnick,

Your points are well taken. There is merit in imaging objects only as they appear to the normal human eye. But you might also allow the scientists and artists to display their work as they see fit… artistic/scientific expression. Artists may wish to communicate something extraordinary and the scientists commonly wish to communicate information out of our normal visual bandwidth because it provides insight into physical makeup.

It’s all cool and necessary for intended communication to be realized.

Hi Sputnick,

Your points are well taken. There is merit in imaging objects only as they appear to the normal human eye. But you might also allow the scientists and artists to display their work as they see fit… artistic/scientific expression. Artists may wish to communicate something extraordinary and the scientists commonly wish to communicate information out of our normal visual bandwidth because it provides insight into physical makeup.

It’s all cool and necessary for intended communication to be realized.[/quote]

True .. and I don't object to it, except that they should clearly indentify their images as altered .. and perhaps include an explanation as to how and why?

Again, excellent point... but we are all human... even scientists.

emc wrote:I wondered about the distant/age thing but figured that galaxies must be different ages??? So I thought a 10X distant one could still be younger.

Hey, Ed, don't give up so easily. I felt the article you quoted contradicted itself, but that doesn't mean you're wrong. I'm fairly certain that distance implies age, but the visual age of an object is entirely different.

If we had an image of an object 13.5 billion ly away, that object would actually be very old, (as old as the universe), but visually it would be very young, a veritable new born. Getting back to the galaxies in question, even though the background galaxy is further away and therfore physically older, its appearance can be that of a younger galaxy.

To think of it another way, images of progressively more distant objects is like plotting a history of the universe and the universe will appear progressively younger.

emc wrote:
It would be nice to be able to do a "flyby" on my way home for supper this evening... but that is not possible ... my tank only holds 14 gallons.

(snip)

Unfortunately 14 gallons would likely, only get you to the space station.

bystander wrote:

emc wrote:I wondered about the distant/age thing but figured that galaxies must be different ages??? So I thought a 10X distant one could still be younger.

Hey, Ed, don't give up so easily. I felt the article you quoted contradicted itself, but that doesn't mean you're wrong. I'm fairly certain that distance implies age, but the visual age of an object is entirely different.

If we had an image of an object 13.5 billion ly away, that object would actually be very old, (as old as the universe), but visually it would be very young, a veritable new born. Getting back to the galaxies in question, even though the background galaxy is further away and therfore physically older, its appearance can be that of a younger galaxy.

To think of it another way, images of progressively more distant objects is like plotting a history of the universe and the universe will appear progressively younger.

I knew that... Chris explained that to me... I just don't know what to think of me sometimes

I reckon I need an astronomy hat to wear or something... to help keep things in.

BMAONE23 wrote:

emc wrote:
It would be nice to be able to do a "flyby" on my way home for supper this evening... but that is not possible ... my tank only holds 14 gallons.

(snip)

Unfortunately 14 gallons would likely, only get you to the space station.

Yeah... and with my navigational skills I would likely wind up trying to dock with Tiros 2

BMAONE23 wrote:Unfortunately 14 gallons would likely, only get you to the space station.

emc wrote:Yeah... and with my navigational skills I would likely wind up trying to dock with Tiros 2

If you can get to the space station on 14 gal, NASA needs you. They can handle the nav.

emc wrote:There is merit in imaging objects only as they appear to the normal human eye.

Not really. To begin with, by imaging at all you are going beyond what the human eye can see. For example, we cannot really see color in galaxies or nebulas. That is true regardless of the size of telescope we use, or how close we could travel towards an object. So is it somehow cheating to provide an image that does show color? Also, images are capable of showing much more contrast on deep sky objects than our eyes are capable of detecting. Another cheat? And images can integrate much longer than our eyes, so the possible S/N is arbitrarily and significantly greater.

In short, we make images of astronomical objects because our eyes cannot see them at all, or can only detect a tiny fraction of the available information.

Arguing for imaging astronomical objects as they appear to the human eye is like arguing for imaging microscopic objects as they appear to the eye. The idea is meaningless.

What is important with a scientific image isn't how it appears with respect to some mythical unaided perception, but what physical truths the image can provide. In what way does this image of the Deer Lick Group misrepresent reality? Well, it isn't photometrically accurate. But that is almost always true of images intended to show physical structure, and that fact is stated in the image description. The intent of the image is to resolve the maximum possible detail, and to represent approximately accurate color (what our eyes would see if the objects were brighter). It succeeds in both respects.

Chris Peterson wrote:

emc wrote:There is merit in imaging objects only as they appear to the normal human eye.

Not really. To begin with, by imaging at all you are going beyond what the human eye can see. For example, we cannot really see color in galaxies or nebulas. That is true regardless of the size of telescope we use, or how close we could travel towards an object. So is it somehow cheating to provide an image that does show color? Also, images are capable of showing much more contrast on deep sky objects than our eyes are capable of detecting. Another cheat? And images can integrate much longer than our eyes, so the possible S/N is arbitrarily and significantly greater.

In short, we make images of astronomical objects because our eyes cannot see them at all, or can only detect a tiny fraction of the available information.

Arguing for imaging astronomical objects as they appear to the human eye is like arguing for imaging microscopic objects as they appear to the eye. The idea is meaningless.

What is important with a scientific image isn't how it appears with respect to some mythical unaided perception, but what physical truths the image can provide. In what way does this image of the Deer Lick Group misrepresent reality? Well, it isn't photometrically accurate. But that is almost always true of images intended to show physical structure, and that fact is stated in the image description. The intent of the image is to resolve the maximum possible detail, and to represent approximately accurate color (what our eyes would see if the objects were brighter). It succeeds in both respects.

Hi Chris,

Your points are well received. I'm glad you're adding to the discussion!

In this APOD forum, all things are typically presented as and are expected to be scientific (except for the occasional musing and the visitors that are skimming the surface… like me). Why not post an APOD now and then of an “imitation” of what the human eye would see if it were capable of zooming in on space objects? You’ve pointed out that it is stark compared to the beauty of the typical [artistic]/scientific enhancement, but I think it would be cool to implement an overlay of an enhanced version or vice-versa to kind of illustrate how science/art can communicate more than what we "normally" see. Food for more thought, if you will.

... but I prefer to see things as they are to our normal senses ...

Adding visual enhancements to an image is a tool used to better observe the structure of an object of interest much in the same way a telescope is used as a tool to make an object appear larger and more detailed. Visible light is a small fraction of the information these objects are sending to us, transposing non-visible energies to the visible is a wonderful and necessary learning tool.

Now if someone were added extra stars to a photo ...

And to answer an earlier question, yes we listen to "space radio" all the time with radio telescopes, the SETI project for one example.

Dr. Skeptic wrote:Adding visual enhancements to an image is a tool used to better observe the structure of an object of interest much in the same way a telescope is used as a tool to make an object appear larger and more detailed. Visible light is a small fraction of the information these objects are sending to us, transposing non-visible energies to the visible is a wonderful and necessary learning tool.

Just for the record, I very much appreciate and enjoy the enhancements that instruments bring out of space objects in the art of presenting science. I'm also blown away by what astronomers are able to decipher!

Dr. Skeptic wrote:Now if someone were added extra stars to a photo ...[snipped]

One of the most attractive things impressing me about astronomy/science is the reputation for presenting factual data perceived in the public sector. (For example, I love how Professor Nemiroff in his lectures readily admits things astronomers/scientists don’t understand... there seems to be lots of theories in astronomy)

Your comment is a good example of how esteemed this pursuit of truth is held. I expect a lot of people are attracted to science for this reason. Thanks for bringing this beautiful paradigm up!

Sputnick wrote:

psyched wrote:

I just wish a photograph was a photograph instead of an artist's conception, which this one obviously is.

It's easy to veer off from discussing things to discussing names of things. What does it matter if the thing in question is called a photograph or a simulacrumgraph or something else? Well, I suppose it can matter when names of things are applied precisely. One would want to distinguish between a photograph and a painting because they were produced differently. These days the term "image" is used more and more frequently, I guess because there are more different ways of producing images than there were in the past. "Image" is a broader term than photograph or painting, for example, and a less precise one in denoting the means of creating the image. "Image" seems to refer more to the impression on the retina of the observer than to the means of creation of the image.

A rose by any other name would smell as sweet.

Our senses don't normally see in the infrared or UV, and if they did perhaps the image in question would look to us somewhat like it appears on apod .. and art of course can imitate reality .. but I prefer to see things as they are to our normal senses. If we begin to alter colours, what stops us from altering squares to circles. If someone wants to present an image on apod which has been digitally altered, then they should at least present it as such. Perhaps your 'rose' quotation is a good example, because with humans altering roses the sweet scent has gone out of most of them.

There are several posts in this thread about the relationship between 'things as they are to our normal senses' (and similar) and (most of) the APOD images; I'm choosing this one to quote pretty much at random.

Let's remind ourselves that even ordinary film photography does not reproduce things as they are to our normal sight ... careful, quantitative analysis of the response curves of human rods and cones+how the brain interprets the signals from them compared with the imaging system that is a typical colour film camera+commercial developer will show, objectively, that there are many differences. Some are subtle, some imperceptible, and some obvious ... for example, colours are more saturated in normal colour film photography. Then there's the 'red eye' in flash photography, especially in photographs from older cameras that worked with just one bright flash - my guess is that Sputnick's album of family snaps includes some (flash) photos that have people with 'red eye' and some that don't.

"If someone wants to present an image on apod which has been digitally altered, then they should at least present it as such". It's worth taking some time to think about this a bit.

For starters, as far as I know, every APOD is a .jpg file, and every image that has been 'JPEG processed' has been digitally altered.

Second, 'digitally altered' in respect of images from instruments (cameras, detectors, etc) aboard spacecraft, such as the HST or MESSENGER, is kinda meaningless, because the images are digital from the get-go and getting them to a ground station necessarily involves alteration.

Third, HST images all have a kind of 'red eye' effect: cosmic ray hits. When a cosmic ray hits a CCD pixel, it causes the well to saturate; if you present the image without digitally altering it to remove these, you'll see lots of annoying white points all over it at random (not just HST images of course, almost all detectors on spacecraft have to deal with this kind of noise).

No doubt Sputnick (and emc?) does not count these three kinds of digital alteration, but why not?

A great many APOD images are from instruments on spacecraft (example, example, example) or contain a component therefrom (example); some are taken by ground-based telescopes that record parts of the electromagnetic (EM) spectrum we humans cannot detect (example). In these the APODs may be accurately described as visual representations of data.

One more thing, composites. Take two APOD examples, NGC 1132 and Cen A. Both deep sky objects can be detected in far more parts of the EM spectrum than just the few wavebands represented in these images - gamma, UV, IR, microwave, ... so these images are visual representations of just a small part of the whole, awesome picture. And just as we need to get above the Earth's atmosphere to 'see' in the x-ray band (and gamma rays, and UV, and (most of the) IR, and ...), there is emission from these objects that we cannot see from our vantage point in this part of the Milky Way galaxy, because it's blocked by the interstellar medium (UV blueward of the Lyman limit, radio redward of the local plasma frequency).

OK, two more things; composites part 2: APOD 7 Oct 2008. It's certainly taken in the visual waveband, but is nothing like what you would see with your own eyes if only they had the resolution, integration time, and contrast of the HST. Why? Because this composite has been created from data taken using several narrow-band filters - it samples only a tiny part of visual waveband that your eyes are sensitive to.

emc wrote:

Nereid wrote:

adrianxw wrote:This galaxy look deformed to me. The centre section seems tilted relative to the outer lying blue spiral arms.

[...]

It could be some kind of optical illusion.

To readers who are not professional astronomers: what sorts of things do you think one could do to go about finding out whether NGC 7331 is, in fact, 'deformed' in some way, in its centre section?

In particular, how could one demonstrate - objectively - that there is some deformation, and, if so, measure the degree of deformation in some quantitative fashion?

It would be nice to be able to do a "flyby" on my way home for supper this evening... but that is not possible ... my tank only holds 14 gallons.

Could the deformation or illusion be demonstrated by measuring each star's position and creating a 3D computer model?

Anyone else like to take a shot at suggesting how one could go about finding out whether NGC 7331 is, in fact, 'deformed' in some way, in its centre section?

emc wrote:Why not post an APOD now and then of an “imitation” of what the human eye would see if it were capable of zooming in on space objects?

Mainly because they're not very interesting to most people. If you want to know what objects look like to the eye, a good source is the sketches many amateur astronomers produce. Have a look at these for example. You can invert them in Photoshop or the like to get a better idea of the actual appearance. They appear quite accurate to me. A telescopic view is exactly the same as what you would see if you got closer. Here's his sketch of NGC7331, and I can tell you from experience that this is quite close to how it actually appears, except that the galaxy itself is a little too bright here.