How come images are gray when you look through an amature telescope?

Question

Why aren't the images of stars in color (blue or orange)? Is it because of the telescope? Or are most telescopes unable to show color images?

Answer 1

Stars can be quite colorful when viewed through an amateur scope. Colorful double stars (e.g. Albireo) show up with beautiful colors in an 11 inch aperture Schmidt Cassegrain. Your eyes would see similar colors if they were 11 inches in diameter. These same stars are seen as only white when viewed with the naked eye (normal sized naked eye) or through a scope with much smaller aperture. The more photons you collect, the more your eyes can see colors. ADDED: Some red giant stars, like Antares , are clearly orange in color even with the naked eye.

In the same sense, nebulae and galaxies can only be seen as gray light patches in an 11 inch, but may reveal traces of color in a 24 or 40 inch scope. Distant objects generally require photographic exposure times in order to collect enough photons to show the brilliant shades that you see in the advertisements and magazines - these can be deceiving.

Answer 2

The human eye is not particularly sensitive to the broad range of colors that celestial objects radiate. It takes special filters to enhance and bring those colors out, like you see in the spectacular images done by the Hubble Space Telescope.

Answer 3

Hi. It is a limitation of your eyes. Can you see red in the dark? Blue? There you go. A camera can store photons over time, or a filter will only allow certain wavelengths to pass. Stacking these images yields a true color image (if done correctly).

Answer 4

Stars appear white for a few reasons.By the time the light reaches us it has very low intensity,so low that our color vision is unresponsive.The color sensitive cells in our eyes (cones) require a bright light source for activation. Even the brightest stars emit barely enough light to stimulate our (cones),so we see stars with our much more sensitive rod cells, but they are colorblind,so our brain interprets this light as white or shades or grey. A larger aperture telescope assists us in collecting more light,that is why observers w/ those big light buckets can pick up color in the orion nebula.
Don't get me wrong, I can see color in double star systems w/ my 60mm refractor,but I prefer the view my 10" dob gives me, which is much, much brighter. This is why most observers have more than one type of telescope beacause there is no one perfect telescope system. Some just do a better job than others at a particular task. I like to think of refractors as being "sharper" and reflectors/cats as being "brighter".
In astronomy, aperture is king.
Another factor in star color perception is that our eyes do not respond to all colors equally. Our eyes contain 3 types of color sensitive cones which in turn are sensitive to different overlapping ranges of colors. The red,blue and green cones are actually more sensitive to voilet,cyan and green so by combining the relative intensities of light absorbed by 2 or 3 types of cones the brain generates our perception of color.
So after the brain processes the combined inputs from the red,green cones we perceive the colors orange and yellow.
The combined response of all 3 types of cones to different colors is called the eye's luminous efficiency. The difference in our visual sensitivity to varying colors influences our perception of star colors. The peak where our eyes perceive the most light of any color is in the yellow/green part of the spectrum and are less sensitive to blue/orange and least to voilet/red. So, light from stars w/peak intensities at short wavelengths will appear to us as more green/yellow than violet/blue.
Another reason is that different stars have different surface temperatures,therefore different peak colors, the hotter the star,the bluer the wavelength of it's peak and the cooler the star, the redder the wavelength of it's peak color but as light travels through any gas (our atmosphere) some of the photons at each wavelength get scattered,the degree of scattering is dependent on wavelength (Rayleigh Scattering). Around 1871 it was soon determined that the shorter a photon's wavelength the more it gets scattered by gas,violet gets scattered most followed by blue green yellow orange red,so stars appear more ruddy than they would w/o the influence of interstellar gas clouds or our atmosphere.
This scattering in our planets atmosphere washes out Arcturus's peak intensity yellow light causing the star to appear reddish orange instead of how it appears on film and to the trained eye when viewed high overhead as a distinctly yellowish hue. So we can see how all these things such as a star's surface temperature/ gas clouds/earth's atmosphere/and our own visual systems come into play as the star light comes from the stars surface to our eyes.

Answer 5

We only see in black and white at very low light levels.

Some stars show colour, and Albireo is a particularly striking contrast.

If emission nebulae show any colour at all they have a greenish cast, partly because they have an important spectral line around 500 nm, and partly because our colour vision is most sensitive to green.