Colour in Nebulas?

[Bongo]

Hi,

I was very happy to be able to observe the Orion Nebular through my new(ish) telescope recently.

I'm very aware that through my modest 'scope, I'm not going to get Hubble-like images. I'm embarrassingly excited to see some 'white wispy stuff' and that's what I'd expected to see.

What I don't understand is why the pics I see online are coloured, whereas the Orion nebular I see is 'wispy white'. Do folks use filters? Or is it 'false' colour? Or would a bigger telescope show colour? Or is it the result of a photographic technique, as opposed to the human eye?

Like I say, I'm more than happy with the wispy stuff - I just don't understand why its different.

[Cornelius Varley]

2 minutes ago, Bongo said:

Hi,

I was very happy to be able to observe the Orion Nebular through my new(ish) telescope recently.

I'm very aware that through my modest 'scope, I'm not going to get Hubble-like images. I'm embarrassingly excited to see some 'white wispy stuff' and that's what I'd expected to see.

What I don't understand is why the pics I see online are coloured, whereas the Orion nebular I see is 'wispy white'. Do folks use filters? Or is it 'false' colour? Or would a bigger telescope show colour? Or is it the result of a photographic technique, as opposed to the human eye?

Like I say, I'm more than happy with the wispy stuff - I just don't understand why its different.

The human eye is far less sensitive to the spectrum than a camera (we don't see the infra red spectrum that digital cameras can) and much of the colour in the photographs you see online is invisible to the naked eye through a telescope. To us, those colourful nebulae are just faint pale fuzzies.

[Pixies]

I'm sure someone will come up with the proper technical description, but basically, the parts of your retina that are very sensitive to low light, do not detect colour. In order to be able to see colour in an object, it must be bright enough.

Children / young adults can detect colour in DSOs that we oldies can't see, either!

[Bongo]

Ah! Unfortunately, getting younger isn't an option for me. If only... 😉

Would I be right in thinking that if I had a telescope with a much larger aperture, or the means to take a longer exposure photo then there would be some chance of colour?

Thanks for the info - much appreciated!

[Jiggy 67]

The pictures you see are the result of multiple long exposure pictures stacked together in software to produce a final result, unfortunately the human eye isn’t capable of that 

[orions_boot]

I have not seen many DSO but the only one I have seen that isn't pale grey and white is 

https://en.wikipedia.org/wiki/Eskimo_Nebula

See if you can find that perhaps?  It is dark green unfiltered, and blue through a oiii filter for me.

[John]

I can see faint tints of colour in some nebulae with my 12 inch aperture dobsonian. Some of the planetary nebulae show a distinct tint (eg: the Blue Snowball NGC 7662) and touches of green in the Orion nebula. But these are few and far between. Most nebulosity is in shades of grey to my 60 year old eye.

 

 

 

[Ships and Stars]

Yes as I understand it, dark adapted eyes only use the B&W portion or region (?) of the rods and cones as they're more sensitive to low light, so everything will be shades of grey when fully dark adapted.

One trick I found from really dark sites that only works momentarily, and somewhat questionably, is to get my eyes partially dark adapted, but not fully, and quickly look into the eyepiece (20" dob) before I dark adapt any more. It's a matter of finding the right balance point. For a fleeting second, I'll catch what I perceive as strong hints of colour. M57 and M42 are the obvious best candidates that spring to mind. M42 definitely showed colour, and M57 appeared a brilliant iridescent blue for a fleeting second. I've had that happen a few times, and it was unexpected but remarkable. This usually happens after subconsciously checking my phone and momentarily losing some dark adaptation. 

So unlike these awesome astrophotos, everything visual observers see will basically be shades of grey unless you have an absolute monster of a telescope (I've heard a 40" dob on up will start to show persistent colour in some nebula) or freakishly good eyesight in the 'rods and cones' department, probably linked more to a youthful age as mentioned above.

 

[vlaiv]

12 minutes ago, Ships and Stars said:

Yes as I understand it, dark adapted eyes only use the B&W portion or region (?) of the rods and cones as they're more sensitive to low light, so everything will be shades of grey when fully dark adapted.

One trick I found from really dark sites that only works momentarily, and somewhat questionably, is to get my eyes partially dark adapted, but not fully, and quickly look into the eyepiece (20" dob) before I dark adapt any more. It's a matter of finding the right balance point. For a fleeting second, I'll catch what I perceive as strong hints of colour. M57 and M42 are the obvious best candidates that spring to mind. M42 definitely showed colour, and M57 appeared a brilliant iridescent blue for a fleeting second. I've had that happen a few times, and it was unexpected but remarkable. This usually happens after subconsciously checking my phone and momentarily losing some dark adaptation. 

So unlike these awesome astrophotos, everything visual observers see will basically be shades of grey unless you have an absolute monster of a telescope (I've heard a 40" dob on up will start to show persistent colour in some nebula) or freakishly good eyesight in the 'rods and cones' department, probably linked more to a youthful age as mentioned above.

 

I think that not being dark adapted is the key more than telescope size - or rather having balance - not being dark adapted so that night vision fully kicks in and being enough dark adapted to see the object.

I think I saw color in M57 with 5" telescope - but it was more "am I really seeing color or just remembering how it is supposed to look like?"

[Ships and Stars]

7 minutes ago, vlaiv said:

I think that not being dark adapted is the key more than telescope size - or rather having balance - not being dark adapted so that night vision fully kicks in and being enough dark adapted to see the object.

I think I saw color in M57 with 5" telescope - but it was more "am I really seeing color or just remembering how it is supposed to look like?"

Agree, there's a balance point somewhere between light and dark adapted where colour is still perceivable, but it must be a very narrow range. I think on CN they were talking about this, and some observers who had the luck to view through truly massive telescopes upwards of 40" had remarked the colour of some nebulae can be reliably maintained and observed if there was enough aperture. I'd guess if a really bright PN like M57 was magnified enough to almost fill the FOV in a giant telescope, your eyes wouldn't fully dark adapt anyway, a lot like a good look at M42 will knock dark adaptation back. Colour in nebulae is an interesting topic! 

Edited January 14, 2021 by Ships and Stars

[Ships and Stars]

@vlaiv I'll selflessly take time out of my busy schedule 🤣 to chase down a willing owner of a 40"+dob, probably somewhere in the American SW or Western Australia, and put this matter to rest! Colour or no colour! 👍

Actually there was the guy who built a 70" dob from a US military spy satellite mirror that was rejected for use because it had a small chip on one edge. I'll phone him up  

[Andy R]

I’ve seen colour when observing the blue snowball planetary nebula (NGc 7662) with a 6” SCT. I think it’s in the constellation of Andromeda so it’s still visible in the early evening sky. It was one of the first DSO’s I observed and was blown away by it. 

[Jiggy 67]

12 minutes ago, Andy R said:

I’ve seen colour when observing the blue snowball planetary nebula (NGc 7662) with a 6” SCT. I think it’s in the constellation of Andromeda so it’s still visible in the early evening sky. It was one of the first DSO’s I observed and was blown away by it. 

I've seen a lot of planetary nebula display colour but maybe that's because, to us, they appear as small points of light (generally) like a star or planet rather than large regions of nebulosity with low surface brightness like other types of nebula

[Bongo]

Wow! Some great info and tips there. Thanks to all!

[saac]

I think you got some great answers there too Bongo.  Some people think they see some very faint colour; my teenage daughter thinks she can detect faint colour in the Orion nebula. Sadly my eyes will only ever see the whisphy ghost like structure you have also seen.  But that alone is amazing so keep enjoying it . Regrettably , no matter what aperture you have you will not see the deep sky objects as they are presented in astrophotography.  Our eyes just don't work that way - they cannot take long exposures.  Are the colours real - well yes they are , remember a colour is a particular frequency of light and the cameras are capable of detecting those frequencies (wavelengths) over a certain range.  As for how representative the colours are in all astrophotographs well that get's very technical very quickly - check out the excellent and thorough contribution vlaiv made in the the post about "authenticity of images". It is a very technical thread but very informative especially if you looking to get into the  higher end of image processing.

Jim  

[faulksy]

from a dark site orion will show green. ring nebula will show colours as john says blue snowball as well. to name just a few. veil in the summer will show maroon as well

[John]

The thought of those lucky enough to be able to observe with a 20 inch scope under really dark skies makes me go a tinge of green as well 

[Ships and Stars]

18 minutes ago, John said:

The thought of those lucky enough to be able to observe with a 20 inch scope under really dark skies makes me go a tinge of green as well 

Haha, you're welcome to visit when all this covid stuff blows over! Hopefully I'll have a semi-permanent home for it on a rural farm or estate by then, and I won't have to lug it around everywhere. If another 500p turns up at the right price and work picks back up, I'm seriously considering making a 500p binoscope.  A lot of 'ifs' I know...

[saac]

20 minutes ago, John said:

The thought of those lucky enough to be able to observe with a 20 inch scope under really dark skies makes me go a tinge of green as well 

To mis quote William    "those few, those happy few , those band of brothers with large aperture dobs "   

Jim 

[faulksy]

@John you can make your own like i did for around 9k

sell some of your finders, sorry i mean apo,s and you will be laughing 🤣

seriously, if you can transport a big dob or have a dark garden it is worth it

[niallk]

The Cat's Eye is another good one for bluey green colour.

I had a funny experience with my old 10" dob: I used to have a 15mm 70° super wide field cheap EP from TS.  M42 was always shades of grey.  Then I purchased a TV N13T6 - wow 1st night M42 was strongly green - and always since.  Only once have I seen pink in M42 in my 15".

[Louis D]

Try shining a bright flashlight (torch) onto a piece of white paper and stare at it to force your rods into the active state then quickly look in the eyepiece at the Orion nebula.  I've managed to catch a brief glimpse of green coloration using this technique with an 8" Dob.

[John]

10 minutes ago, Louis D said:

Try shining a bright flashlight (torch) onto a piece of white paper and stare at it to force your rods into the active state then quickly look in the eyepiece at the Orion nebula.  I've managed to catch a brief glimpse of green coloration using this technique with an 8" Dob.

I believe some planetary observers use a similar technique to help discern subtle planetary detail and tones.

 

 

[Pixies]

Checked out the Eskimo nebula this evening and I do see it as green, but I wonder if that's my expectations playing tricks with me.

M57 (Ring) sometimes appears blue/green, too. Again, I think that's the same thing.

[Bongo]

13 hours ago, Louis D said:

Try shining a bright flashlight (torch) onto a piece of white paper and stare at it to force your rods into the active state then quickly look in the eyepiece at the Orion nebula.  I've managed to catch a brief glimpse of green coloration using this technique with an 8" Dob.

Wow! That seems counter-intuitive initially. but I'll give it a go as soon as these pesky clouds clear.

Sounds like, to summarise, to see colours in a nebula requires one or more of the following:

• Good/young eyes
• Massive aperture
• Fancy photo techniques
• Good dark site

I hasten to re-state that I don't particularly mind that I don't see the colours, and probably never will with my existing scope, site and eyes. I think my question about why that is, though, has been well answered. Thanks folks!