Can you see DSOs in colour just with your eyes?

[Carbon Brush]

12 hours ago, John said:

When I've been doing outreach sessions with my 12 inch dobsonian I've noticed that younger eyes seem generally more sensative to seeing colour in astro targets than mine are. Some older observers struggle to see even the colour different in the binary Albireo for example wheras the youngsters shout out the colour difference between the stars often without prompting.

 

Yes John. A decline in night vision generally with age is well known and documented.

I should have got more into visual astronomy years ago - sigh.

[Ben the Ignorant]

Almost all the brighter globulars look bluish to me, with varying degrees of greyishness depending on the telescope and conditions. Sometimes they appear so bright they border on white but I don't know if that qualifies as color.

The most popular planetaries all have a clear bluish or greenish tint (without filter) to my eyes, also in various shades depending on the scope and conditions. The mighty Lagoon Nebula seems to have a very pale bluish look in large binoculars but only when transparency is great. And galaxies with strong surface brightness look either whitish grey or definitely blue, the most striking memory of this is the NGC 4485/4490 close pair in Canes. 

Through the rural astroclub's Celestron 11 they had an unquestionable blue tint, but from the city or through a smaller scope they were just grey smudges.

[JOC]

It might be worth taking a look at all the pictures on page one of this thread.

 

[MarsG76]

I agree with the posts... red is simply a color to which our eyes are not sensitive enough... I did read about some amateurs that reported seeing pale pink hues in the Orion Nebula when using 30" mirrors... 

 

[Stub Mandrel]

I have read, and subsequently prooved to myself, that it's possible to see colour in the moon IF your eyes are totally non-dark adapted, forcing you to view it only with the colour receptors. You can make out just very faint tones to the seas.

[Ben the Ignorant]

1 hour ago, Stub Mandrel said:

it's possible to see colour in the moon IF your eyes are totally non-dark adapted, forcing you to view it only with the colour receptors. You can make out just very faint tones to the seas.

With very large exit pupils, in the 4mm to 5mm range, they are not that hard to see.

[JOC]

Mars is not a DSO, but if you want some colour variety it def. Has a pinkish hue in a large enough scope.  There are also a number of stars that a def different colours too to enjoy, I think the double star Alberio is a good one to start with as they are different colours iirc.  FWIW the so called 'blue snowball' does always seem def blue rather than white/grey to me.

Edited July 3, 2019 by JOC

[MKHACHFE]

So, reading the replies, is it safe to say that, yes, some colour towards the blue end of the spectrum can possibly be seen with (maybe) younger eyes? I mean, I'm 43 and would bet cash i saw blue in the Cat's Eye Nebula (NGC 6543 in Draco) two nights ago.

Is the general consensus a yes? It's an interesting question to be sure. I told my wife the other night that the colour in the beautiful astrophotography images we see is fake, so she asked what the REAL colour of these DSO's are...and i had no answer. Is there even an answer? I know most of the detail in the images comes from wavelengths shorter and/or wider than visible light. 

 

Cheers

[michael.h.f.wilkinson]

I have seen hints of green and purple in M42 and M57, and the Blue Snowball is indeed a bit blue, but the clearest colour I have seen is with Olly Penrice's 20" Dob under brilliantly clears skies was in the Saturn Nebula: It was a really vivid blue-green. No O-III filter needed. I saw the Ring nebula on the same night with the same scope, and it too showed colour, but nothing like the Saturn Nebula 

[Alexandros]

First of all, WOW so many posts, thank you all for the insightful replies! I am delighted to find out that it is possible to see faint hues and more, when it comes to DSOs. My initial expectations were that it was not at all possible, so this is a very pleasant surprise. I managed to get a glimpse of the Omega Nebula, it was an uncontainable thrill to see the internal bright triangular portion of it. Sadly, it sits at the skies right above Piraeus and Athens, so the light pollution is literally something that depresses me (I sometimes look at the hills around me and see the skyglow, it's like the sky is gray and not black). I am sure the reason it appeared orangey was because of that and not its actual colour. I was unable to see the lagoon and eagle nebula because of this.

I am gonna try my hand at planetary nebulae, but I am unsure if my 130mm newtonian would be able to see them. I hope in the future I will be able to upgrade my gear and get the observations flowing much more easily. Thank you all for the tutorials and links, I will be sure to read them. 

Seeing michael's observation summary, a new question has arisen. What about supernovae? Can you see colour in them? What is the most colourful/ contrasty object you've ever seen?

[John]

From Greece, your 130mm newtonian should show the planets somewhat better than we are getting the here in the UK. You will be able to see all 7 planets with that scope when they are in good positions in the sky. With good seeing you should see some detail on Jupiter, Saturn and Mars at opposition. 4 moons at Jupiter, maybe 5 at Saturn on a good night. The phases of Venus and Mercury will be visible and Uranus and Neptune as distinct but very small disks rather than pin points as stars are.

Supernovae have never appeared as more than faint point sources to me even with my 12 inch scope - like a faint star that was not visible before and does not tend to stay visible for long. All the ones we have seen recently have been in other galaxies so far, far away. The last to be observed in our galaxy was in 1604 I believe. I was not around then !

 

[Stub Mandrel]

10 hours ago, MKHACHFE said:

Is the general consensus a yes? It's an interesting question to be sure. I told my wife the other night that the colour in the beautiful astrophotography images we see is fake, so she asked what the REAL colour of these DSO's are...and i had no answer. Is there even an answer? I know most of the detail in the images comes from wavelengths shorter and/or wider than visible light.

The colour in RGB images is 'real' just typically with the saturation turned up so pale colours become stronger. Like redoing a subtle watercolour in poster paint 🙂

The odd thing is that in general they would look the same if you were closer to them as although closer the light would come from a much more spread out source.

[Ricochet]

10 hours ago, MKHACHFE said:

Is the general consensus a yes? It's an interesting question to be sure. I told my wife the other night that the colour in the beautiful astrophotography images we see is fake, so she asked what the REAL colour of these DSO's are...and i had no answer. Is there even an answer? I know most of the detail in the images comes from wavelengths shorter and/or wider than visible light. 

Not necessarily true. Most of the matter in the universe is hydrogen so much of the emission is Ha emission. As an example here is is the visible spectrum for the Orion nebula:

http://stars.astro.illinois.edu/sow/ori-neb-p.html#spec

You can clearly see the Ha, OI and SIII lines in the spectrum as well as the Hb and OIII lines. When you look at the nebula through a telescope you might see it as green, but in photos it is mainly red and the reason for the difference is the difference between your night and day vision. The graph below shows the sensitivity of the three different colour cone cells used during the day and the rod cells used at night (dotted line):

So you can see that if the nebula was bright enough all of the red emission would be seen by the red cone cells, but because it is dim, they aren't triggered when we view it through a telescope. We can however, detect some green, because the green cells and rods are much more sensitive at the Hb and OIII wavelengths. For dimmer nebulae only the rods are stimulated and hence we only see them in black and white.

 

[Ben the Ignorant]

4 hours ago, Alexandros said:

I am gonna try my hand at planetary nebulae, but I am unsure if my 130mm newtonian would be able to see them

Start with NGC 7662 in Andromeda, it's so intensely bright blue you can't miss it. Just use enough magnification, but that reduces the hunting field, or be prepared to watch for anything that's not as tight as a star, averted vision helps. I've observed it with my 127mm from my city a couple months ago, and though I know it well, the ease with which it pierced light pollution stunned me again.

[MKHACHFE]

10 hours ago, Stub Mandrel said:

The colour in RGB images is 'real' just typically with the saturation turned up so pale colours become stronger. Like redoing a subtle watercolour in poster paint 🙂

The odd thing is that in general they would look the same if you were closer to them as although closer the light would come from a much more spread out source.

I have to say, I'm surprised by that. I was under the impression my whole life that the colour in the imagery was faked....No doubting you, in fact, I'm going to read more about it after reading your reply.  Cheers!

[MKHACHFE]

9 hours ago, Ricochet said:

Not necessarily true. Most of the matter in the universe is hydrogen so much of the emission is Ha emission. As an example here is is the visible spectrum for the Orion nebula:

 

 

I'm only replying to this line, but the rest of your post was very informative, thank you. 👍

Regarding what I wrote, I suspect that  i was thinking of radio and xray astronomy where the detail really comes out with other wavelengths. I seem to remember an image of what a certain galaxy looked like in visible light and then in xray/gamma and there was so much more to see...Because of that, i just assumed that the same applied to all stellar objects. 

Thank again for your informative post. 

 

Cheers

[rwilkey]

On 01/07/2019 at 20:08, John said:

Some older observers struggle to see even the colour different in the binary Albireo

Hi John, one of the reasons I got into double stars is because you can see colour, I love looking at Albireo and the Easter-egg double in CAS (Ʃ 60) for example, and I think I am a bit older than you!

[John]

10 minutes ago, rwilkey said:

Hi John, one of the reasons I got into double stars is because you can see colour, I love looking at Albireo and the Easter-egg double in CAS (Ʃ 60) for example, and I think I am a bit older than you!

I seem to be quite good at detecting relatively small brightness differences but I'm not so good at spotting subtle tints. Maybe I ought to get into variable star observing ?

[rwilkey]

12 minutes ago, John said:

I seem to be quite good at detecting relatively small brightness difference

I am amazed that I can still separate Mizar & Alcor with the naked eye, when my kids and many others struggle. 

[niallk]

I saw M42 as strong green in my 10" - but only when i got my N13T6 - never with my GSO 15mm 70 deg EP! In my 15" I've seen tinges of pink on the edges of the 'wings' too.  The Blue Snowball does indeed appear blue, and the Cat's Eye strongly blue-green.  I think I recall the Omega neb looking light green to me (with an O-III), and the Emerald neb too.

[Sunshine]

11 hours ago, rwilkey said:

I am amazed that I can still separate Mizar & Alcor with the naked eye, when my kids and many others struggle.

Great to hear you have eyes like a falcon, good thing to have.

[Mike JW]

Hi All,

Some Planetary Nebula will be seen as blue and greenish in colour with scope upwards of 8". In my 20 the colours were just brighter. DSOs are never bright enough for our eyes to pick up colour. Some times we convince ourselves we are seeing colour. Star colour is an interesting lark. Folk will see the colour of stars differently - just read through any definitive guide about viewing coloured stars/doubles and you will realise just how subjective colour is. So called red stars for me normally appear more orange than red.  Also when looking at coloured doubles the colour and brightness of the main star will influence how we see the colour of its companion. So called hot blue stars I see as white but the more I look then I pick up the blue in the flaring. I find the Great Red Spot on Jupiter another good example of "exactly what the colour is" - I do see it as "red" but more like reddy brown.  Uranus is blue but more a greeny blue. Hubble/images in general give a misleading picture of what can be seen in the night sky.

"Ships and Stars" - don't expect a blaze of colour from PNs even in a dark sky - just enjoy the brightness of everything through a 20" A mate of mine when he first looked at M42 through his 24 lost his dark adaption!!!!

Mike (E. Anglia)

[Erling G-P]

On ‎01‎/‎07‎/‎2019 at 21:08, John said:

When I've been doing outreach sessions with my 12 inch dobsonian I've noticed that younger eyes seem generally more sensative to seeing colour in astro targets than mine are. Some older observers struggle to see even the colour different in the binary Albireo for example wheras the youngsters shout out the colour difference between the stars often without prompting.

 

This might explain something that's been puzzling me.  When I turned 14, I was given a modest refractor; 60mm  and f=1000mm.  Used it a lot back then, but have had active observing on the backburner for many years.  Last August I finally got a bigger telescope which I've coveted all the way since then: A SW 200PDS; with the main purpose of getting into imaging.  Have observed a little with it though, and have wondered why all stars appear virtually colourless white - I recall the colours being much more vivid in the old refractor; Albireo for example.  In the new scope, I can perceive a difference between the two stars, but it's just a subtle blue and orangeish toning, more than a stand out spectacle.  Based on John's comment, it's probably the 40 years of wear my eyeballs have accumulated, more than the scope, which is to blame.. (If only you could be refurbished like an old house or car...)

Regards,

Erling

[Mike JW]

Erling - you are absolutely right about eyes getting old and diminishing ability to discern colour. I am much further down the path than yourself ........... Mike

[Ags]

1 hour ago, Erling G-P said:

If only you could be refurbished like an old house or car..

Cataract surgery. Gets rid of cataracts obviously, but also gets rid of the dark yellow filter all old eyes have.