Minimum apperture for colors

[Nova2000]

What is the minimum apperture required to observe colors of Dso In a very dark sky? 

Rajesh 

[Stu]

A lot depends upon eyes and conditions, but I've seen greenish tones in M42 in a 4" scope.

[John]

Similarly to Stu, I can see very slight tints of colour in a couple of deep sky objects with my 4" scope and these are a little more pronounced when I use my 12" scope. Younger eyes seem to perceive colour slightly better (I'm in my 50's now) but visually we never seem to be able to compete with imaging. The majority of my observing seems to be in shades of grey. I have observed occasionally with a 20" scope under reasonably dark skies and largely objects remained colourless to my eyes.

[Chris]

Generally speaking most DSO's are so faint that it is difficult to see colour whatever the aperture. The human eye isn't very quantum efficient compared to a camera sensor. If you want to see colour then you can maybe look into video assisted astronomy, or plain old astrophotography. There are sections for both on stargazers lounge with lots of info  

Like stu, I can see green in M42 with a modest scope owing to it being a very bright DSO, and a touch of colour in M57 with an 8" scope.  

[Paul73]

Good question. I was wondering about that too.

DSO are generally white whatever the scope. For the Nebulea, I guess that the colour receptors in our eyes don't fire up until things get bright.

Ignoring chromatic abrasion (looks like an enthusiastic disco), sky certainly seems more colourful in bigger scopes. Agreed, a green tinge creeps into M42 at 5" (nothing for me at or below 4"), at 10" there can be hints of purple as well. At 16" it gets more pronounced but I'm not sure that I have seen colour in any other DSO. The Veil can look Red, but I think that this is down to the filter.

Paul

[Nova2000]

So filters such as O3 and UHC show color? 

[Nyctimene]

You can find some distinct green/blue-green/turquoise colours when you observe some planetary nebulae, e.g. the Saturn nebula NGC 7009 in Aquarius, the Cat's Eye nebula NGC 6543 in Draco , or the Blue Snowball nebula NGC 7662 in Andromeda. The colours can be seen best when using a UHC or O III filter. Carbon stars, as R Leporis (Hind's Crimson Star), or W Orionis show a vivid orange or red colour. Otherwise, not much colour can be found when observing DSO's.

Stephan

[Moonshane]

Bear in mind that when people refer to seeing colour they are in most cases talking about subtle hints of tinge rather than bright colours. e.g. you might get something a bit like this with a big scope

you will never see anything like this visually no matter what you use

[ollypenrice]

I use a 20 inch at a dark site and only see colour in the small bright planetaries. I see none in M42 though I do see a lot of faint nebulosity.

An OIII filter is likely to make everything look slightly (or very) green because OIII lies on the blue-green border. Look through an OIII in the daylight and you can see it's a green filter.

Star colour can be seen naked eye, though, very easily.

Olly

[Paul73]

The Blue Snowball does look blue!

Re Filters - they only let through certain wavelengths, so it is not the real colour that one might see with super vision. I.e. Using a Solar Continuum filter, m With Transmition Reducing tools, the sun looks bright green.?

Paul

[Moonshane]

It's part of the real colour though . The reason it looks green is that the wave length it lets though is green 

The reason Oiii filters makes things look turquoise.......and Ha red........etc 

[LukeSkywatcher]

Apparently women can see colours better than men. This would explain why more female astronomers say they can see hints of colours in DSO such as M42 etc. IIRC, it is also only men who suffer from colour blindness. 

I have no hard evidence or links to back this up. Its just a couple of things i have read or seen on tv over the yrs.

[ollypenrice]

11 minutes ago, LukeSkywatcher said:

Apparently women can see colours better than men. This would explain why more female astronomers say they can see hints of colours in DSO such as M42 etc. IIRC, it is also only men who suffer from colour blindness. 

I have no hard evidence or links to back this up. Its just a couple of things i have read or seen on tv over the yrs.

There are, exceptionally, colour-blind women. I was married to one! (I'm a terrible colour... but she didn't mind. )

Olly

[spaceboy]

For me atmospheric seeing and transparency has always been the deciding factor not necessarily the size of the scope. I really struggle to see any colour 80% of the time but then there are some OK nights where I see a hint of colour. In the 10 years I have been observing I have only seen obvious colour once but I tell you what that night is engraved in my memory. I just wish it would happen again as it really does make it all worth while.

[LukeSkywatcher]

6 minutes ago, ollypenrice said:

There are, exceptionally, colour-blind women. I was married to one! (I'm a terrible colour... but she didn't mind. )

Olly

She obviously did mind, because you said you were married to her.

 

[Dave In Vermont]

Under pretty dark skies, I used to regularily see reds and blues in M42 with a 3" F15 Achromatic Refractor. However I was between 12 and 14 years old at the times.

Best wishes,

Dave

[N3ptune]

For me with 200mm aperture: The cat's eye nebula is green, the blue snowball is bluish, Orion's great nebula is green. Omega nebula I see it green also. Plus many blue, white, beige, yellow and orange stars, that's not exactly boring, there are many colors available.

[JOC]

So far for me M42 is err.....grey!  Jupiter is nicely striped and pink! Betelgeuse is a rather snazzy golden orange, and the best most flashy object in the sky is still the monster raving party star - Sirius - green, blue, red, white flashing and scintillating for all its worth!

[Moonshane]

I do agree about the blue snowball. It's surprisingly blue. I seem to recall NGC6210 in Hercules being noticably green too. Planetaries are certainly the most likely candidates for colour other than planets of course.

[JOC]

Warning - thick newbie moment here - Q.  What is a 'Planetary' as opposed to a 'planet' as per Moonshane's post above please?

[Moonshane]

sorry I should have said planetary nebula (sometimes referred to as PNs). They are smaller stars like our sun that have popped and turned into small bright nebulae like the ring, the dumbbell etc.

[Moonshane]

I think they are so called as they are usually small and round like planets but have nothing to do with them really.

[JOC]

Many thanks Moonshane!  :-D

[Moonshane]

ps when I said like our sun, I was referring to smaller not popped 

[Stu]

The Blinking Planetary (NGC6826) is another good one, looks green to me. In a smaller scope the Nebula shows well with averted vision, then if you look at the central star directly it disappears, hence the 'Blinking' tag