Astronomy question

[Evariste Euler Gauss]

Anyone on here expert enough (or able to ask any sufficiently expert friend) to answer this general query?

So, those amazing images that Hubble has produced of all kinds of stunning phenomena in deep space - the kind of things you see if you do a Google Images search for "Hubble images of space".

They're so exotic, with a hugely diverse colour palette and wacky stuff like clouds and so on, that they bear no resemblance whatever to stuff we can see ourselves through telescopes.

I understand that the technology which generates the images involves collecting light from very long "exposure", if that's the right term here, as well as all sorts of cleverness to get the magnification of things that are so far away that it's beyond imagination, in remote galaxies. But what I want to know is: do the things in the images actually look like the images? In other words, if a hypothetical human observer were sufficiently close to the things in question, galaxies or whatever, would that observer be able to look into the void and see things that shape and colour with his or her human eyes? Or are the images just some kind of "notional" representations, translations of data about light waves into some easily digestible image which could never actually be seen like that?

[hobbes]

Astronomy question

From the Hubble team themselves...

Taking color pictures with the Hubble Space Telescope is much more complex than taking color pictures with a traditional camera. For one thing, Hubble doesn't use color film — in fact, it doesn't use film at all. Rather, its cameras record light from the universe with special electronic detectors. These detectors produce images of the cosmos not in color, but in shades of black and white.
Finished color images are actually combinations of two or more black-and-white exposures to which color has been added during image processing.
The colors in Hubble images, which are assigned for various reasons, aren't always what we'd see if we were able to visit the imaged objects in a spacecraft. We often use color as a tool, whether it is to enhance an object's detail or to visualize what ordinarily could never be seen by the human eye.

[Evariste Euler Gauss]

Astronomy question

Thanks Hobbes! That final paragraph you've quoted seems to mean that the answer to my question is, a lot of the time, "no they don't"!

[hobbes]

Astronomy question

With regards to more traditional astrophotography, it's a more nuanced question.
Short answer, yes that's what you'd see. To an extent. The reason we see grey smudges is that the amount of light our eyes can collect is rather small. And has no "memory" as it were. Astrophotography uses extremely long exposures onto a CCD chip that does remember each photon.
So it can see and record all of the light that hits it over the exposure length.
However, astrophotographers tend to want to draw out certain features or bandwidths of light to accentuate what they're shooting. So they'll usually (for deep sky) use a black and white camera and take multiple long exposure using colour filters (RGB to start then specific filters like Hydrogen Alpha or Oxygen 3) which give the colour. These exposures are then stacked onto each other for the final image.

[hobbes]

Astronomy question

Incidentally, astrophotography is an outrageously expensive pastime.
Not only do you need a rock solid mount, perfectly polar aligned that can track the target. You also need a guide scope with a camera fixed on a point that can communicate with the mount to make tiny changes so you don't get elongated stars or field rotation.
You need a computer to "train" the mount for cyclical errors in the gears to again avoid distortions.
You need a decent scope with great optics and probably a field flattener to flatten the image to the CCD.
You need a decent camera (anywhere from £200 - £10k) preferably cooled so for long exposures you don't get infrared bleed onto the CCD. Or if it's a DSLR then you need it adapted for IR cutout.
You need a series of filters to filter what you get. And you need the patience of a saint to run the exposures and to process the images afterwards and to not kill everyone in a 5 mile radius if it clouds over half way through your imaging run.
You could in theory do it for a £700 or £800 quid if you bought all the stuff used and weren't overly fussy.
But the guy who took the pics I linked to above had 2 rigs, one of which the mount ALONE cost £7k.
It's not for me. I'll stick to looking, myself.

[Rogin the Armchair fan]

Astronomy question

There seems to be no real consensus - from people I've met who've seen them, or even from photographs - on whether glaciers are white, or sky blue.

[hobbes]

Astronomy question

Well, blue, obviously.

[Patrick Thistle]

Astronomy question

As you get older you see more bluely (as it were) due to changes in the eye. So it might depend how old your glacier spotters are.

[Patrick Thistle]

Astronomy question

Regarding the OP, things like 'clouds' or 'pillars' of gas would be very hard to see 'close up' because if you were close to them they would be so vast you would be in them and not notice. A bit like how we can't take pictures of our own galaxy.

[hobbes]

Astronomy question

Patrick Thistle wrote: Regarding the OP, things like 'clouds' or 'pillars' of gas would be very hard to see 'close up' because if you were close to them they would be so vast you would be in them and not notice. A bit like how we can't take pictures of our own galaxy.

True dat. The Pillars of Creation are billions of mile long.

[San Bernardhinault]

Astronomy question

As Hobbes has already answered - basically, the answer is probably not. The people at Hubble are generally assigning colours to wavelengths or to emission spectra.

The pillars of creation composite pic was broken down like this:
green for hydrogen, red for singly ionized sulfur and blue for double-ionized oxygen atoms

[Gangster Octopus]

Astronomy question

San Bernardhinault wrote: sulfur

You've gone native...

[San Bernardhinault]

Astronomy question

I have, yes. But that was just a C&P.