APOD: The Hubble Ultra-Deep Field in Light... (2018 Mar 05)

[Chris Peterson]

So with something like the Hubble Deep Field, does someone or software go around to each little blob and let only that light through a prism to get the elemental spectrum?

This image (product? presentation?) was apparently produced from older data, acquired using multiple bandpass filters. There are much better data available now, released last year, in the form of a full visible light spectrum for every pixel in the HUDF. It would be interesting to see this redone with that data.

[rstevenson]

Would be so nice if the sound could be turned on on my browswer. No such luck. Any suggestions?

I also hear no sound, though I get the magnifying glass thingy, and the sound is definitely on in my browser

You need to use Chrome or Firefox (not Safari), and make sure that you don't have anything blocking autoplay (which many people do, because normally that last thing anybody wants is videos or sound clips that start playing by themselves when you land on a page).

Oh well. Last year I switched from my former best browser, Firefox, to Safari because FF was just getting too buggy and sluggish. I won't bother switching back just to hear this. (I presume Safari won't do it because the code that runs the sound is Java, and Apple and Java just don't get along.)

Rob

[Chris Peterson]

I also hear no sound, though I get the magnifying glass thingy, and the sound is definitely on in my browser

You need to use Chrome or Firefox (not Safari), and make sure that you don't have anything blocking autoplay (which many people do, because normally that last thing anybody wants is videos or sound clips that start playing by themselves when you land on a page).

Oh well. Last year I switched from my former best browser, Firefox, to Safari because FF was just getting too buggy and sluggish. I won't bother switching back just to hear this. (I presume Safari won't do it because the code that runs the sound is Java, and Apple and Java just don't get along.)

Well, it's not like you can only have one browser installed.

[rstevenson]

You need to use Chrome or Firefox (not Safari), and make sure that you don't have anything blocking autoplay (which many people do, because normally that last thing anybody wants is videos or sound clips that start playing by themselves when you land on a page).

Oh well. Last year I switched from my former best browser, Firefox, to Safari because FF was just getting too buggy and sluggish. I won't bother switching back just to hear this. (I presume Safari won't do it because the code that runs the sound is Java, and Apple and Java just don't get along.)

Well, it's not like you can only have one browser installed.

I have five browsers installed. What I meant was I can't be bothered switching to see (or hear, in this case) something that should have been offered in a universal format, and well tested, in the first place. This is the web, not a proprietary walled garden.

Rob

[Chris Peterson]

I have five browsers installed. What I meant was I can't be bothered switching to see (or hear, in this case) something that should have been offered in a universal format, and well tested, in the first place. This is the web, not a proprietary walled garden.

Unfortunately, there isn't always a universal format, especially for something peculiar like this APOD.

[geckzilla]

Rob. ...Rob. It takes 5 seconds to copy and paste the URL and look at it in another browser. And I'm sorry to say but web developers stopped caring much about Safari a long time ago.

I will note that I recently borrowed a little MacBook, looked at the latest updates to the OS, and very prominently displayed in one of the slides was the fact that Safari will now, like Chrome, block sounds that play automatically. I had to switch to Firefox, too.

And it's javascript. Not java. Big difference.

[rstevenson]

Rob's Internet Forum Rule: any mention of universal web standards in relation to any product ever made by Apple will result, with a likelihood approaching 100%, in a putdown of said product from another forum member.

Rob

[geckzilla]

Apple's great, Rob. It's just that this is a Safari issue (and also apparently a Chrome issue) and not something anyone can do much about. I'm sorry it seemed like I was personally attacking you or your use of Apple products, though. I often feel like a second-class citizen with my Windows machine because almost none of the astronomy software works with Windows. Feels bad.

[geckzilla]

And, just to explain a bit more why developers stopped "caring" about Safari... it stopped being supported by Apple for non-Apple OS'es a long time ago. So for web developers who don't actually own a Mac, this erected a serious barrier to testing it.

[Cousin Ricky]

Oh well. Last year I switched from my former best browser, Firefox, to Safari because FF was just getting too buggy and sluggish. I won't bother switching back just to hear this. (I presume Safari won't do it because the code that runs the sound is Java, and Apple and Java just don't get along.)

I’m using Firefox (on openSUSE GNU/Linux), but I disabled Java years ago. I still get beautiful piano music.

[Cousin Ricky]

(Our own retina cone cells only run from 430 nm to 572 nm and are unable to distinguish
a broad green black body star like the sun as actually being green as opposed to white.)

This can’t be right. We can easily see wavelengths from 400 nm to 700 nm, and published cone sensitivity data run from 380 nm to well above 700 nm.

The reason the Sun appears white instead of green is a matter of interpretation of the differentials of the signals from our 3 types of cone cells. The Sun’s spectrum is rather broad in the visible range, and the amount of green isn’t all that much higher than that of other wavelengths. More generally, to say that the Sun is “actually” green is meaningless; color literally does not exist until your brain creates it.

Solar spectrum

Cone sensitivities (normalized)

[Chris Peterson]

(Our own retina cone cells only run from 430 nm to 572 nm and are unable to distinguish
a broad green black body star like the sun as actually being green as opposed to white.)

This can’t be right. We can easily see wavelengths from 400 nm to 700 nm, and published cone sensitivity data run from 380 nm to well above 700 nm.

Indeed. The numbers given represent the approximate peak sensitivity for the short and long wavelength cone cells, not their actual sensitivity range.

[rstevenson]

And, just to explain a bit more why developers stopped "caring" about Safari... it stopped being supported by Apple for non-Apple OS'es a long time ago. So for web developers who don't actually own a Mac, this erected a serious barrier to testing it.

True, but any developer who willfully ignores the #3 most used browser on the desktop and the #2 browser on tablets* is really not doing their job properly. Also, WebKit is the underlying engine for Safari, and a fork of WebKit is used by Chrome and Opera among others, which makes not caring about Safari perilous indeed.

Okay, I'll stop. Back to our regular programming.

Rob

[neufer]

(Our own retina cone cells only run from 430 nm to 572 nm and are unable to distinguish
a broad green black body star like the sun as actually being green as opposed to white.)

This can’t be right. We can easily see wavelengths from 400 nm to 700 nm, and published cone sensitivity data run from 380 nm to well above 700 nm.

And the HUDF filters that run from 435 nm to 1600 nm are also somewhat sensitive outside this range.

However, my point is that individual black body temperature spectra are:

1) close to being monochromatic when using 7 filters spanning 1.88 octaves
2) but far from being monochromatic when using 3 filters spanning 0.41 octaves.

The HUDF is colorful because the spectral range of observation has expanded from 0.41 to 1.88 octaves.

[Ann]

(Our own retina cone cells only run from 430 nm to 572 nm and are unable to distinguish
a broad green black body star like the sun as actually being green as opposed to white.)

This can’t be right. We can easily see wavelengths from 400 nm to 700 nm, and published cone sensitivity data run from 380 nm to well above 700 nm.

The reason the Sun appears white instead of green is a matter of interpretation of the differentials of the signals from our 3 types of cone cells. The Sun’s spectrum is rather broad in the visible range, and the amount of green isn’t all that much higher than that of other wavelengths. More generally, to say that the Sun is “actually” green is meaningless; color literally does not exist until your brain creates it.

Solar spectrum

Cone sensitivities (normalized)

I agree with you, Cousin Ricky.

But I also think that the cones in our eyes have evolved into seeing the Sun as white. It makes sense to "interpret" sunlight as white, because it contains all colors (except for the absorption lines, but you know what I mean), so sunlight allows us to see the "combined color" of the reflected light of any object that reflects light between 400 and 700 nm. Objects that preferentially reflect green light (505-570 nm, such as grass) never look white to us, unless they reflect the other optical wavelengths too in such a way that they mimic the solar blackbody curve.

But the fact that the Sun looks white to us, even though it is "technically" green, is also the reason why no other stars ever look green to us. For us to see an object as green, it must reflect or emit strongly in the green part of the spectrum, and be quite dark otherwise.

Ann

[geckzilla]

And, just to explain a bit more why developers stopped "caring" about Safari... it stopped being supported by Apple for non-Apple OS'es a long time ago. So for web developers who don't actually own a Mac, this erected a serious barrier to testing it.

True, but any developer who willfully ignores the #3 most used browser on the desktop and the #2 browser on tablets* is really not doing their job properly. Also, WebKit is the underlying engine for Safari, and a fork of WebKit is used by Chrome and Opera among others, which makes not caring about Safari perilous indeed.

Okay, I'll stop. Back to our regular programming.

Keep in mind that "not caring" about it also comes about because it is so standards compliant. Things rarely go awry. I think, however, that you are completely missing the point I was trying to make, because my tone was not respectful enough for you. I think I may have found a solution for you anyway, given a few more moments to look into it. The problem may be caused by the iframe. Viewing the content of the iframe on its own seems to get the sound to play. https://apod.nasa.gov/apod/image/1803/A ... /hudf.html

Edit: You also have to go to Safari Preferences => Websites => Auto play and allow apod.nasa.gov to play sounds. See? It's not a coding issue. It's a Safari issue.

Edit 2: Ahah, you don't even have to view the iframe separately in Safari. It works just fine on the APOD page itself once the exception is added. Chrome has one added issue, apparently.

[rstevenson]

Thanks for that. I was aware of that option. If APOD gets in the habit of posting this kind of music video, I may try it, but then I'd have to turn the sound off every time someone adds an innocuous (they think) sound track to their night-sky time-lapse vid.

There is, however, one thing someone -- whether the content creator or the host website, I'm not sure -- can do. They can provide a widget so users don't have to be even that minimally knowledgeable. When I view a video on Youtube, for example, I see in the top-left corner a clickable Unmute button. Not sure how that's implemented, but it's one of the things some developer does to make their content truly universally accessible, to all browsers on all OSes, including iOS and the many flavours of Android. As the web fractures into smaller and smaller user groups, the task of universality of content becomes harder and harder.

Rob

[geckzilla]

content truly universally accessible, to all browsers on all OSes, including iOS and the many flavours of Android

This has long been the goal of web development, and many, many hours of tweaking, and rewriting entire scripts to get it to happen, but there's always something that keeps it from being universal... Something that didn't get tested... Either a browser setting, or an addon, or old code, or a novel device, whatever... This muting of autoplay is a relatively new thing, too. The important thing is that we are humans, and we are far more adaptable than any software, and we can find a way around minor inconveniences or contact developers directly if feeling ambitious. I hope anyone who encountered the same problems we did was able to find a way to enjoy it, because it was a very enjoyable APOD.

[MarkBour]

I found lots of 28.8, and a couple of 13.1,s. What I foun interesting is that some of the older ones seemed to be intertwined with much closer objects. Could we be looking we be looking 'down' the length of 'filaments' of a big-bang stream of matter that only looks like a group from our perspective? There seems to he a lot of them.

What? Lots of 28.8 ? That's going to be a few octaves down ...