Chris Peterson wrote: ↑Mon Jul 12, 2021 9:34 pm
stefanz wrote: ↑Mon Jul 12, 2021 9:14 pm
Chris Peterson wrote: ↑Mon Jul 12, 2021 4:02 pm
I meant it just as I stated it. No telescope of any size can make an object brighter. If it allows you to see a hint of color,
it is only because it covers more retinal cells, which provides more signal. A matter of biology, not optics.
Of course, an object does not emit more photons if we increase the optics (which seems to be what you mean).
Whether we can see colors (that was the question) depends on whether we receive enough photons for the cone cells (responsible for color vision and less sensitive than the rod cells which are responsible for monochromatic vision at low light levels). How much photons we receive depends from the aperture of the optics. Otherwise astronomers could save a lot of money by purchasing the smallest telescopes they find on Ebay.
The number of photons a rod or cone receives does not increase with aperture.
The number of photons one's own pupil receives does, in fact, increase with aperture.
(Duo-pupil binoculars doubles this.)
However, the greater the ratio between a telescope's primary objective diameter
to the diameter of one's own pupil the more those photons get spread out over ones retina such
that: "
The number of photons any single rod or cone receives does not increase with aperture."
http://www.seasky.org/astronomy/astronomy-messier.html wrote:
<<Although many deep sky objects can display a wide array of colors in long exposure photographs,
the human eye is not sensitive enough to see most of these colors through a small telescope. The[se] photos are presented in black and white to
best represent the view that would be seen through a telescope.>>
https://astronomy.stackexchange.com/questions/28837/can-we-see-the-color-of-nebulae wrote:
Can we see the color of nebulae?
sanaris wrote:
<<YES and NO.
YES, you will get "color" of nebulae. Reason of this is that because of very low luminosity for small diameter telescope, your eye is using "grey vision". When luminosity will reach certain level, your eye will start adopt color receptors. Good luminosity levels begin from diameters above 200mm.
NO, that "color" which you may observe does NOT have anything in common with colors which you see everywhere. Because most nebulae emitting in near-infrared and ultra-blue regions, which when mixing, give "greenish" light. But this color is result of your brain mixing different wavelengths, not actual green wave. Some people see it green, others see "pink" etc...>>
adarsha joisa wrote:
<<I have been able to see color in the Orion nebula (M42) with my 16 inch dobsonian from a heavily light polluted city. This is only in the center ([apparent magnitude: 4.0] trapezium area), where I can see a reddish color. Interestingly, it's much more difficult to see this red color from a dark location. Several other people in my astronomy club have also noticed this, and one explanation that I got was that the cone cells are still active in a light polluted city, so I'm able to notice the red color ( I don't know whether it's true). From a good dark location, I've seen color on many planetary nebulae such as the Ghost of Jupiter. You usually see these are greenish in color, if you have a suitably large scope. With my 16 inch, I've seen color in a small number of bright objects (almost always limited to greens), but most objects don't show color. Having observed in instruments ranging from 2 inch to 18 inches, it certainly seems like a larger aperture allows you to see color in a larger number of objects. In my personal experience, I've only been able to notice color in the brighter objects in scopes 16 inches and above.>>
[quote="Chris Peterson" post_id=314908 time=1626125658 user_id=117706]
[quote=stefanz post_id=314907 time=1626124492 user_id=145318]
[quote="Chris Peterson" post_id=314900 time=1626105745 user_id=117706]
I meant it just as I stated it. No telescope of any size can make an object brighter. If it allows you to see a hint of color,
it is only because it covers more retinal cells, which provides more signal. A matter of biology, not optics.[/quote]
Of course, an object does not emit more photons if we increase the optics (which seems to be what you mean).
Whether we can see colors (that was the question) depends on whether we receive enough photons for the cone cells (responsible for color vision and less sensitive than the rod cells which are responsible for monochromatic vision at low light levels). How much photons we receive depends from the aperture of the optics. Otherwise astronomers could save a lot of money by purchasing the smallest telescopes they find on Ebay.[/quote]
The number of photons a rod or cone receives does not increase with aperture.[/quote]
The number of photons one's own pupil receives does, in fact, increase with aperture.
(Duo-pupil binoculars doubles this.)
[b][u]However[/u][/b], the greater the ratio between a telescope's primary objective diameter
to the diameter of one's own pupil the more those photons get spread out over ones retina such
that: "[i][color=#0000FF]The number of photons any single rod or cone receives does not increase with aperture[/color][/i]."
[quote=http://www.seasky.org/astronomy/astronomy-messier.html]
<<Although many deep sky objects can display a wide array of colors in long exposure photographs, [b][u][color=#0000FF]the human eye is not sensitive enough to see most of these colors through a small telescope[/color][/u][/b]. The[se] photos are presented in black and white to [b][u]best[/u][/b] represent the view that would be seen through a telescope.>>[/quote][quote=https://astronomy.stackexchange.com/questions/28837/can-we-see-the-color-of-nebulae]
[c][size=150][color=#0000FF]Can we see the color of nebulae?[/color][/size][/c]
[quote=sanaris]
<<YES and NO.
YES, you will get "color" of nebulae. Reason of this is that because of very low luminosity for small diameter telescope, your eye is using "grey vision". When luminosity will reach certain level, your eye will start adopt color receptors. Good luminosity levels begin from diameters above 200mm.
NO, that "color" which you may observe does NOT have anything in common with colors which you see everywhere. Because most nebulae emitting in near-infrared and ultra-blue regions, which when mixing, give "greenish" light. But this color is result of your brain mixing different wavelengths, not actual green wave. Some people see it green, others see "pink" etc...>>[/quote][quote=adarsha joisa]
<<I have been able to see color in the Orion nebula (M42) with my 16 inch dobsonian from a heavily light polluted city. This is only in the center ([apparent magnitude: 4.0] trapezium area), where I can see a reddish color. Interestingly, it's much more difficult to see this red color from a dark location. Several other people in my astronomy club have also noticed this, and one explanation that I got was that the cone cells are still active in a light polluted city, so I'm able to notice the red color ( I don't know whether it's true). From a good dark location, I've seen color on many planetary nebulae such as the Ghost of Jupiter. You usually see these are greenish in color, if you have a suitably large scope. With my 16 inch, I've seen color in a small number of bright objects (almost always limited to greens), but most objects don't show color. Having observed in instruments ranging from 2 inch to 18 inches, it certainly seems like a larger aperture allows you to see color in a larger number of objects. In my personal experience, I've only been able to notice color in the brighter objects in scopes 16 inches and above.>>[/quote][/quote]