Author Topic: More Information for Hubble Zoo (beta)  (Read 34617 times)

oswego9050

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Re: More Information for Hubble Zoo (beta)
« Reply #15 on: June 08, 2010, 09:27:39 pm »
This is going to be great!  Merci beaucoup!!!  ;D ;D ;D 
"Absence of evidence is not evidence of absence." - Carl Sagan

lpspieler

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Re: More Information for Hubble Zoo (beta)
« Reply #16 on: June 08, 2010, 10:11:05 pm »
Now I know what the linked wavelength indications are for  ;D

You might want to add a short explanatory text below the user interface. Some people might fail to notice that magnitude and Kron/Petro-radius change when clicking the wavelength indications. It's also not clear whether the picture was taken in the wavelengths available on the info page or if these wavelengths were just used in determining radius and magnitude.

cheers

Bruno

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Re: More Information for Hubble Zoo (beta)
« Reply #17 on: June 09, 2010, 09:00:44 am »
My wishes come true...thanks Mike.... :) ;) :D ;D
Ciao
Bruno

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Stellae in caelo sunt radiosae

JeanTate

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Re: More Information for Hubble Zoo (beta)
« Reply #18 on: June 09, 2010, 02:13:58 pm »
This is a very, very welcome development!  ;D

The redshift values need some sort of caveat, especially for those which are merely photo-z.

For example, AHZ100039o lists the redshift as 0.570593, which apparently comes from the DEEP2 work, specifically the DR3, and that lists its observed z ("utilizing the DEIMOS  spectrograph on the Keck  II telescope") as 0.570610 +/- 0.000028 (not quite the same, but close enough).

On the other hand, AHZ30001im lists the redshift as 0.940300, which is apparently a photo-z, and so has a much larger uncertainty than its six significant figures suggests.

paulrogers

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Re: More Information for Hubble Zoo (beta)
« Reply #19 on: June 09, 2010, 06:24:55 pm »
What?? I can't seem to get my head around how this redshift thing works! u, g, r, i, z? If those are shortest to longest wavelength, is u blue and z red? What do the numbers actually tell me? I clearly have no idea what I'm talking about. Can anyone point me to an idiot's guide to redshift?  ???

Two different things here.  CCD-like devices, whether in your digital camera or HST, are fundamentally "monochrome" light detectors.  When photons hit the photoelectric material, electrons are "bounced loose".  Measure the charge and you know the light intensity.  Colored "filters" are deposited over individual detector pixels, making each sensitive to a certain range of nearby wavelengths.  That's because the colorant has a certain narrow absorption band, in the broad range of the total spectrum.  Imagine if they were precise to one wavelength.  Emissions of that precise wavelength would get through, "light", and every other wavelength would be "dark".  Not very useful, for general purposes.  But that's what the ugriz thing means.  Different ranges of the spectrum the detectors can see, filtered into different "narrow" but not precise "bands".  Think for a minute how your monitor and TV give the impression of full color
with just red, green, and blue sub-pixels.

When it comes to measuring red-shift you need something different.  Now there exists one precise wavelength produced by an electron jumping from a higher energy state in an atom to a lower energy.  The photon carries off the difference.  We know where it should be, for a given set of local conditions.  We can create those in a lab.  In a Hubble expanding universe the Doppler, i.e. "red", shift will make that wavelength appear longer.  For this we use Newton's prism, or a diffraction grating, to spread out the light of different wavelengths, so we can, in effect, slide our detector along, measuring the intensity at different wavelengths.  The difference between where we measure it to be, from where we know it should be, gives us our red-shift.

Make sense now?  :)
« Last Edit: June 10, 2010, 03:55:02 pm by paulrogers »

paulrogers

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Re: More Information for Hubble Zoo (beta)
« Reply #20 on: June 09, 2010, 06:53:11 pm »
Some people might fail to notice that magnitude and Kron/Petro-radius change when clicking the wavelength indications. It's also not clear whether the picture was taken in the wavelengths available on the info page or if these wavelengths were just used in determining radius and magnitude.

I'm still not clear on why I particularly care about the radius.  What's the use of it?

Michael Parrish

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Re: More Information for Hubble Zoo (beta)
« Reply #21 on: June 09, 2010, 07:56:01 pm »
Just a quick poll, is anybody having any javascript or java problems with the new pages?

paulrogers

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Re: More Information for Hubble Zoo (beta)
« Reply #22 on: June 09, 2010, 08:00:56 pm »
Just a quick poll, is anybody having any javascript or java problems with the new pages?
Aye, but then you knew that. ;)

lpspieler

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Re: More Information for Hubble Zoo (beta)
« Reply #23 on: June 09, 2010, 08:02:07 pm »
all working fine for me :)

JeanTate

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Re: More Information for Hubble Zoo (beta)
« Reply #24 on: June 09, 2010, 08:05:25 pm »
Some people might fail to notice that magnitude and Kron/Petro-radius change when clicking the wavelength indications. It's also not clear whether the picture was taken in the wavelengths available on the info page or if these wavelengths were just used in determining radius and magnitude.

I'm still not clear on why I particularly care about the radius.  What's the use of it?
You don't need it; but it is interesting information.

For example, it may tell you (or suggest) that the object is, in fact, an extended source (a.k.a. galaxy), even though it appears to be a point source (a.k.a. star, quasar).

swengineer

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Re: More Information for Hubble Zoo (beta)
« Reply #25 on: June 10, 2010, 06:38:01 am »
Is there anyway to translate the "old" object IDs into the new ones? 

For example, I'm interested in learning more about the object below. 
But I only know about it by someone else having posted it in one of the forums. 
It is not in my favorites or my history of classifications.

Thanks much. 

-Mark


http://zoo-hst.s3.amazonaws.com/90023363.jpg

 

Budgieye

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Re: More Information for Hubble Zoo (beta)
« Reply #26 on: June 10, 2010, 08:39:51 am »
Some people might fail to notice that magnitude and Kron/Petro-radius change when clicking the wavelength indications. It's also not clear whether the picture was taken in the wavelengths available on the info page or if these wavelengths were just used in determining radius and magnitude.

I'm still not clear on why I particularly care about the radius.  What's the use of it?
You don't need it; but it is interesting information.

For example, it may tell you (or suggest) that the object is, in fact, an extended source (a.k.a. galaxy), even though it appears to be a point source (a.k.a. star, quasar).

galaxies with a lens closely wrapped around them will have an unexpectedly large radius.

Michael Parrish

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Re: More Information for Hubble Zoo (beta)
« Reply #27 on: June 10, 2010, 03:18:23 pm »
Is there anyway to translate the "old" object IDs into the new ones?

For the sake of all of the information shared using the old ids, I've set it up to also accept those in the url.
For instance, 90023363 can be accessed at http://www.galaxyzoo.org/examine/90023363 which serves up AHZ40003tz.

I'll admit we were hesitant to do this, since we don't really want people feel it's necessary to use extra information for classification.  So just check up on the galaxy after you classify it.  :)

Rick Nowell

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Re: More Information for Hubble Zoo (beta)
« Reply #28 on: June 10, 2010, 03:32:38 pm »

JeanTate

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Re: More Information for Hubble Zoo (beta)
« Reply #29 on: June 10, 2010, 09:35:03 pm »
Is there anyway to translate the "old" object IDs into the new ones?

For the sake of all of the information shared using the old ids, I've set it up to also accept those in the url.
For instance, 90023363 can be accessed at http://www.galaxyzoo.org/examine/90023363 which serves up AHZ40003tz.

I'll admit we were hesitant to do this, since we don't really want people feel it's necessary to use extra information for classification.  So just check up on the galaxy after you classify it.  :)
Thanks!

I rather doubt that many zooites will 'read up on' a galaxy before classifying it (but I could be wrong); is there any way you could tell?

For me, the best thing about this is the ability to find out more about an object that someone else has posted, in one of the many Hubble threads.