Starship Asterisk*

by **Anthony Barreiro** » Wed Feb 26, 2014 11:30 pm

After an informative discussion with Margarita, I've realized that this image makes a lot more sense to me as a picture of Gould's Belt, with the Pleiades providing backlighting, rather than as a picture of the Pleiades per se.

by **Nitpicker** » Wed Feb 26, 2014 6:13 am

Hats off to you Mr Lane. I've seen many images of The Pleiades, but none anywhere near as deep and dusty. An heroic effort.

by **Chris Peterson** » Wed Feb 26, 2014 12:45 am

Boomer12k wrote:Please excuse my interruption...but what is Gegenschein again???

In such a system...would there not be a more noticeable effect?

No, because the gegenschein is backscatter off of interplanetary dust particles. The solar wind would largely keep a large bubble around a star moving through such a cloud free of interstellar dust. The particles responsible for the gegenschein and for the zodiacal light are quite large- on the order of a millimeter. Interstellar dust is more on the order of a micrometer, or even smaller, so it is much more affected by solar wind and radiation pressure.

by **Boomer12k** » Tue Feb 25, 2014 11:39 pm

Please excuse my interruption...but what is Gegenschein again???

In such a system...would there not be a more noticeable effect?

:---[===] *

by **Anthony Barreiro** » Tue Feb 25, 2014 10:34 pm

geckzilla wrote:Thanks for coming here and answering those questions for us, Dave.

Yes, thank you!

by **MargaritaMc** » Tue Feb 25, 2014 9:53 pm

geckzilla wrote:Thanks for coming here and answering those questions for us, Dave.

Yes, thank you very much, Dave. As you know, I think the image is exquisite.
Margarita

This is the submission thread info for this image, which I didn't think to look for earlier:
http://asterisk.apod.com/viewtopic.php? ... 50#p220680

by **geckzilla** » Tue Feb 25, 2014 9:10 pm

Thanks for coming here and answering those questions for us, Dave.

by **drlane** » Tue Feb 25, 2014 8:57 pm

Hi everyone. Thanks for all the kind words. Ill give you more of the details. This was actually shot with a QHY 12 which is a OSC camera. There is just over 45 hours of exposure. Since this is a OSC camera its really the equivalent of 135 hours of RBG data. There were about 10 hours of 20 minute exposures and 10 hours of 15 minute exposures I think that really helped with the dust. The rest were 5 and 10 minutes subs. I gathered them from mid November till early January. The telescope was a Williams Optics GTF refractor of 81mm aperture.

I just happen to love M45 and really wanted to get as much detail as was humanly possible from down here on earth. The imaging was taken about 80 miles south of Kansas City in a pretty remote area. No towns over 100 population for 20 miles. It has very favorable skies.

I'm glad you all enjoyed it and I do feel very honored to have it chosen. Thank you all and a big thanks to APOD and all NASA does.

Dave

by **kcstars** » Tue Feb 25, 2014 8:19 pm

On a local site he says:

"Its 45 hours of exposure, 10 hours of 20 minutes exposures and 10 hours of 15 minutes exposures. The rest is split 5 and 10 minute exposures. It was shot with a QHY12 OSC camera at my farm site." . . . and "Oh and a Williams Optics GTF 81 refractor for the scope."

Dave is a wonderful photographer who has taken to his new hobby with great passion (and he does fine outreach for his local astronomy society). I am happy to have a couple of his milky way shots over National Park scenes.

HOpe he can come online and give better more detailed answers.

by **MargaritaMc** » Tue Feb 25, 2014 6:48 pm

Anthony Barreiro wrote:My, that is awfully dusty! I wonder why the Pleiades don't look like that to the naked eye or through binoculars. I guess another way of asking the same question is, what was done to make this photograph show the dust so clearly. Chris already suggested there would be a long exposure. I'm guessing that the brightness of the stars is greatly suppressed and the brightness of the dust is greatly enhanced. Please forgive my uninformed speculations, but this is a remarkably curious image.

I've emailed the photographer (his email address is on the Apod)and he said that he would try to drop into the forum to answer these questions. He mentioned what sounded to me (a non photographer) like very long exposure times. But hopefully David will be able to explain himself.
M

by **Chris Peterson** » Tue Feb 25, 2014 6:45 pm

Anthony Barreiro wrote:My, that is awfully dusty! I wonder why the Pleiades don't look like that to the naked eye or through binoculars. I guess another way of asking the same question is, what was done to make this photograph show the dust so clearly. Chris already suggested there would be a long exposure. I'm guessing that the brightness of the stars is greatly suppressed and the brightness of the dust is greatly enhanced. Please forgive my uninformed speculations, but this is a remarkably curious image.

Getting the dust into the data is simply a matter of collecting enough photons, which is determined by aperture and exposure time. Actually displaying this very large dynamic range data on a limited dynamic range display is a matter of creating the appropriate intensity transfer function (called "curves" in Photoshop and many other image processing programs). You can't tell how bright the brighter stars are in this image, because they're completely saturated. They'd look the same if they were 1000 times brighter (well... not exactly, because they'd show more bloat, but that's how it would be in a perfect world). You can't make a photometric comparison between a saturated pixel and an unsaturated one.

by **Anthony Barreiro** » Tue Feb 25, 2014 6:18 pm

My, that is awfully dusty! I wonder why the Pleiades don't look like that to the naked eye or through binoculars. I guess another way of asking the same question is, what was done to make this photograph show the dust so clearly. Chris already suggested there would be a long exposure. I'm guessing that the brightness of the stars is greatly suppressed and the brightness of the dust is greatly enhanced. Please forgive my uninformed speculations, but this is a remarkably curious image.

by **Chris Peterson** » Tue Feb 25, 2014 5:04 pm

jsanchezjr wrote:Now that you mention it, what can do a cloud of dust if pass near ours Solar System or our Sun? I don't know. I have no idea but one thing that I'm sure is that we are privileged of living in a quiet neighborhood like the one we are living.

It wouldn't do a thing. In our many orbits around the galaxy, the Solar System has certainly passed through areas of dense dust. The densest dust clouds are still hard vacuums, and no match for the wind streaming fron the Sun (not that it would matter, though, even if it made it to the inner system).

Quiet is good, but it isn't determined by dust, rather by not lingering too long near regions of active star formation.

by **geckzilla** » Tue Feb 25, 2014 4:59 pm

If our eyes evolved to see green light up to UV light instead of red light up to blue light, blue would be in the middle of our visual spectrum and look greenish while UV would be our blue and green would be our red. Well, red is very important so I can't imagine a situation where red light would be omitted by a visual organ. Then again, a lot of animals on Earth see UV light. Do their eyes reject longer wavelengths such as red light because UV is more important to them or do they usually perceive a broader spectrum than we do? The most astonishingly complex and precise eyes known in the animal kingdom are mantis shrimp's. We are all colorblind compared to the mantis shrimp.

by **Boomer12k** » Tue Feb 25, 2014 4:53 pm

Whew.....got to get out the broom again....

:---[===] *

by **jsanchezjr** » Tue Feb 25, 2014 4:48 pm

JohnD wrote:I presume that a planet around one of the Pleiades would be unaffected by that dust cloud.

But what would their night sky look like? Fantastical, surely?
John

Now that you mention it, what can do a cloud of dust if pass near ours Solar System or our Sun? I don't know. I have no idea but one thing that I'm sure is that we are privileged of living in a quiet neighborhood like the one we are living.

José

by **Ann** » Tue Feb 25, 2014 4:19 pm

Chris wrote:
There's no getting away from the fact that color is perceptual, not physical.

That's certainly true. Electromagnetic radiation, photons and different wavelengths all exist "out there", but the colors that some of them trigger in our perception exist only in our brains.

And how our brains interpret these wavelengths has everything to do with what the "electromagnetic landscape" has been like where we have come into existence through evolution.

Ann

by **Chris Peterson** » Tue Feb 25, 2014 4:03 pm

gazedandamused wrote:Does anyone know which telescope this image was taken with or a link to a bigger image of it. I've never seen this view of the pleiades and with all the extra detail and dust visible in this image I'm assuming it is from one of our newer ground based telescopes.

A small refractor (Williams Optical GTF81), 81mm aperture, 535mm focal length. Full image resolution is 2 arcsec/pixel, which is right around the theoretical resolution of the optics (slightly degraded because of the color sensor). I'd guess the exposure length was at least a couple of hours, required by the small aperture.

by **Chris Peterson** » Tue Feb 25, 2014 3:52 pm

JohnD wrote:But what would their night sky look like? Fantastical, surely?

It's easy to see. Take a look at the Pleiades some evening with a pair of binoculars. That's what the night sky would look like from there. Almost exactly like it looks here, with the addition of a handful of bright bluish-white stars.

by **Boomer12k** » Tue Feb 25, 2014 3:50 pm

Wow, that is allot of detail. just great!!! A show of light and dust. So simple, yet so Amazing!

:---[===] *

by **Chris Peterson** » Tue Feb 25, 2014 3:50 pm

Ann wrote:And even if we couldn't spot the softly glowing bluish dust, we would be able to see, if we orbited one of the B-type Pleiads, that our skies looked very blue, and the sunlight didn't look yellow at all.

Except if we evolved there, we'd probably see the light illuminating the ground as neutral, thus "white", and the direct sunlight as shifted away from neutral towards red, thus "yellow". There's no getting away from the fact that color is perceptual, not physical.

by **Ann** » Tue Feb 25, 2014 2:38 pm

This is a truly, truly lovely APOD.

The picture really demonstrates how there is dust everywhere in the vicinity of this most famous of star clusters, and how the hot blue stars just light up (and compress and stratify) the dust they happen to encounter.

Like Rob said, the dust is nevertheless very tenuous, and we wouldn't see it at all with our naked eyes if we happened to reside on a planet in orbit around a star belonging to the Pleiades cluster. But I have to wonder if we might not have been able to see the brightest knot of the Merope Nebula, brilliantly visible here in a photo by Volker Wendel, Josef Pöpsel and Stefan Binnewies. At least we should have been able to spot it during a "Merope eclipse"!

And even if we couldn't spot the softly glowing bluish dust, we would be able to see, if we orbited one of the B-type Pleiads, that our skies looked very blue, and the sunlight didn't look yellow at all.

At least until our eyes adjusted.

Ann

by **rstevenson** » Tue Feb 25, 2014 2:02 pm

JohnD wrote:I presume that a planet around one of the Pleiades would be unaffected by that dust cloud.
But what would their night sky look like? Fantastical, surely?

I think only if they had eyes that were quite different from ours. Reflection nebulas like this do reflect light in the visible spectrum, but it's a very thin nebula, hence any local part of it relects only a tiny amount of light. We can photograph it because we're so far away that we are looking at all of it, all the way through -- and, of course, because we're making extended exposures. But from a planet around one of M45's stars, you'd be looking at a fair approximation of a hard vacuum. Photography would help you deduce that your stellar system is passing through some gas and dust, but with the naked eye? Nada.

Rob

by **BDanielMayfield** » Tue Feb 25, 2014 1:56 pm

The links about Gould's Belt (particularly the first) were amazing! I had never heard of this before.

Bruce

by **JohnD** » Tue Feb 25, 2014 1:05 pm

I presume that a planet around one of the Pleiades would be unaffected by that dust cloud.

But what would their night sky look like? Fantastical, surely?
John

Starship Asterisk*

APOD: The Pleiades Deep and Dusty (2014 Feb 25)

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