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Can't see any DSOs in colour


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Under really dark skies and good seeing you will just start to pick out colours in the brighter DSO's with a scope of 8" and above, maybe a good ED frac.

The reason that we cannot define colour at night is nothing to do with the scope for the main part, but our eyes.

The human eye has 2 types of optic cells in them, namely Cones and Rods. We have far more rod photoreceptor cells in our eyes which allow us to see at night but they are less sensitive to colour than the cone cells.

This is why we have trouble descerning colour at night. therefor the larger the aperture of a telescope, the more light it gathers and the brighter the image so the cone cells start picking out the colour of bright DSO's.

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My 8-year-old son, on looking at M42 through the telescope for the first time, and with no prior knowledge of the object, said 'It's bright green!'. So, I think it's an age thing too.

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My 8-year-old son, on looking at M42 through the telescope for the first time, and with no prior knowledge of the object, said 'It's bright green!'. So, I think it's an age thing too.

True Luke, your eyes do deteriorate with age. The best way to preserve them is to sleep a lot during the day and only come out after dark, avoid all bright light sources too ;):D:D

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My 8-year-old son, on looking at M42 through the telescope for the first time, and with no prior knowledge of the object, said 'It's bright green!'. So, I think it's an age thing too.

Thats brilliant!

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I too have heard that colour becomes visible in these mega-scopes.

To the OP: you may want to try taking a trip to dark skies. Your skies may not have direct light pollution and are good for the SE, but in absolute terms they are pretty light polluted. Try to get to the north norfolk coast or better yet to Wales. You won't see colour but the views will make you **** yourself. :icon_salut:

I would love to get out to really dark skies - but not much room in the boot for the scope on holidays with the dog & the kids' bikes in there! Have seen unbelievably dark & clear skies in Suffolk, so I know what I am missing :D

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My eyes are now suffering with age but only my close up vision, I still have very good long range vision and usually surprise the optician, which is good because I'm diabetic and take quite a few pills for my illness. Do short sighted people see as good as long sighted people when using a telescope? Sounds a dumb question but I had to ask lol

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I'm pretty short-sighted but I can at least see as far as the eyepiece :icon_salut:

I don't think eyesight prescription makes much difference to observing except possibly astigmatism (because it says so on the Televue website), but quite how this manefests I am not sure. You just twidle the focus knob until the image looks sharp.

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Keep in mind that for some of these brighter DSO's that may display some color (M27, M42, M57), being dark-adapted actually HURTS your ability to perceive color. Certainly, age and your own eyes' color perception make a difference. But your eyes have three stages of vision: photopic (color/dattime), scotopic (black and white/dark) and mesopic, which is kind of a "halfway in between the two". This is where you want your eyes to be when looking at these DSO's. Try having a light intentionally on, or look at a white light 30 seconds before looking into the eyepiece at these objects.

You want your eye to be in a chemical state where it CAN perceive color and the cones (not rods) are the ones doing the light detection. I've done this and seen a decent amount of color in M42, even seeing blue in a scope as small as 70mm.

Transparencey matters too; skies just after a rain has come through a best. This won't work for everyone, but it will increase your odds, I should think.

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Well, I should clarify. For the very brightest ones in which you might spot some color with enough aperture and transparency (M27, M42, M57), it may help to have some extraneous light nearby to you. Light pollution itself doesn't help.

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The only time I have ever seen colour in a DSO was on the Blinking Planetary nebula in Cygnus I believe. I was viewing with a 15" dob and it was quite distinctly green to my eyes. Even in my 8" on the same night it showed some colour.

Outside this, I don't think I see any colour at all in DSO'S, and not really on planets either. Many people talk of salmon pinks and browns on Jupiter, I just see shades of grey. Plenty of detail, but still grey!

With the naked eye, I obviously do see star colours, plus Mars is very obviously orange/red. With a Neodymium filter it shows a pale pink colour, without it, very pale or no colour.

As has been said, it varies alot with your vision and brain's perception of colour.

Stu

Stu

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when i look at orion through the 16 i can see turquoise color in the center with a bit green pretty. with he ring neb it looks bluey smoke ring that's about all i have seen any sort of color in

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I find that planetary colours show noticably more strongly with my refractors than they do with my newtonian even though the latter has more aperture. I guess this is because of the contrast that an unobstructed optical system can deliver.

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Just proved an interesting point about cones and rods etc. I put the scope out early, when it was still light and had a peak at mars. As I said earlier, I normally don't see much colour at all through the scope on mars, but in the daylight it was a distinctly pink colour.

Stu

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My eyes are now suffering with age but only my close up vision, I still have very good long range vision and usually surprise the optician, which is good because I'm diabetic and take quite a few pills for my illness. Do short sighted people see as good as long sighted people when using a telescope? Sounds a dumb question but I had to ask lol

The answer is yes. Because you adjust the focus of the scope and eyepiece to suit your eyesight.

I have looked through other peoples scopes and had to adjust the focus because they could see it clearly for their eyesight but it was blurred for me until I adjusted it slightly.

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John, the contrast shouldn't be worse in your reflectors due to the obstruction so probably some other reason is underlying the difference. e.g. It may be that one combination of exit pupil and magnification is more conducive to seeing certain details than is another combination.

The secondary obstruction results in an insignificant decrease in contrast when it's under 20% by diameter. i.e. the telescope will perform as though unobstructed. Even for obstructions larger than that, the effect is a reduction in contrast compared to an unobstructed telescope of the same aperture. The obstruction will have to be very large indeed for a big telescope to have worse contrast than a smaller unobstructed scope. Mirror quality, such as roughness, will have more of an effect on contrast than the obstruction.

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Alberio is clearly seen as a blue and gold double star - and the Ring has a blue tinge to it (as per Mikes avatar). These are the only two dso's in which I've seen colour. Betlegeuse has a reddish tinge but for the rest of it planets are the only things I've seen in colour. I've heard the larger scopes like 20" plus allow limited colour to be detected in some brighter nebulae. But it's all black and white really - pun intended lol :)

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My feeling is that the planetary colours are more washed out through my 10" Newtonian than my 5" refractor (both 1200mm FL) because the view is just so much brighter.

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Stu: me too. The most green I've ever seen in M42 was at around dusk. When I'm very dark adapted I don't see those green shades. Then again, the thing is red so the green is an artifact.

It's not so much that it's only "red" or "green" - it gives off electromagnetic waves across a wide spectrum (including ones we can't see). A camera is more likely to pick up red for a variety of reasons; one, it doesn't chemically change due to darker conditions like our eye does! Also, different types of film or chips pick up red (and other colors) differently. The important thing to remember for humans is that under dark sky conditions, the spectrum of light you are least sensitive to is... red! So unsurprisingly, we use red flashlights to see our star charts.

Any wonder then that we don't see much red in M42?

Conversely, the wavelengths where our eyes peak in darker conditions is green. Again, not terribly surprising that among the brightest DSO's we see through telescopes, the colors our eyes perceive most readily are... green (and sometimes blue).

So the green in M42 is not an artifact. It is actual light in that spectrum. In fact, M42 gives off a lot of light in the Oxygen III spectral lines - right in the "green" portion of the spectrum. It's just your eyes are much less likely to perceive red than green in darker conditions (and M42 does also emit in hydrogen alpha, in red, which photos pick up), so the red spectrum doesn't get picked up by the cones in our eyes, but the green does (for some of us, and the younger we are, the more likely we are to see it).

This link gives a pretty close representation of what I see on a really transparent night with my 10" reflector (though I see more orange and pink than red). It also explains a bit about the spectral lines better than I do:

The Trapezium in M42

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