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  #1  
Old 12-04-2012, 02:21 AM
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From which aperture colors in nebulas ?

Many observers say that from 40cm aperture, colors are visible in (bright) emission nebulas like M42 or NGC 3372.
But some claim a 20cm shows colors in the Orion nebula. I see no more than pale bluish with my 25cm Dob.
I see the Carina Nebula with a 10cm just monochrome as the aperture is too small I think.

Planetaries are a different story, I can see a clear blue color in the Cat Eye nebula NGC6543 with a 10cm but it looks more like a blue star more blue than an O or B star. In a 25cm Dob I see a small bluish ball. This one has a high surface density.

What are your experiences ?
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  #2  
Old 12-04-2012, 08:07 AM
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jjjnettie (Jeanette)
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Just a couple of nights ago I was showing my 2 eldest boys M42 through my 10"Dob. I asked them what colours did they see. Jack who is 14, saw shades of pink and Jim who is 26, saw shades of green.
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  #3  
Old 12-04-2012, 08:46 AM
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astroron (Ron)
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Quote:
Originally Posted by skysurfer View Post
Many observers say that from 40cm aperture, colors are visible in (bright) emission nebulas like M42 or NGC 3372.
But some claim a 20cm shows colors in the Orion nebula. I see no more than pale bluish with my 25cm Dob.
I see the Carina Nebula with a 10cm just monochrome as the aperture is too small I think.

Planetaries are a different story, I can see a clear blue color in the Cat Eye nebula NGC6543 with a 10cm but it looks more like a blue star more blue than an O or B star. In a 25cm Dob I see a small bluish ball. This one has a high surface density.

What are your experiences ?

Seeing Colours in deep sky objects is more down to your own colour perception under very low light conditions.
I see Pink in the Orion Nebula, Red in PN IC 418, and only Grey/white in the Eta Carina nebula.
Also I think you have to train your eye to see colours, as they are very subtle.
Cheers
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  #4  
Old 12-04-2012, 11:34 AM
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CosMos (Rich)
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have seen red in M42 in a 20cm.
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  #5  
Old 12-04-2012, 07:12 PM
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I can imagine a slightly greenish tinge to M42 in my 16". It hasn't seemed more pronounced when I've viewed it through 22". Other emission nebulae only ever appear grey. PN - now that's a different story.
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  #6  
Old 14-04-2012, 05:40 PM
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My experience is that from about 10-12 inches I am able to see fairly distinct colour in M42. I see it as a greenish hue. As the aperture increases, the green becomes more emerald to my eyes. In both 18 and 20 inch scopes, whilst the heart of M42 remains green to my eyes, I begin to see pinks/peaches in the outer reaches. For some reason, this effect seems more pronounced when M42 is lower on the horizon. Go figure??!!

I have only seen colour in other bright nebulae from 18 inches and above. M8 is distinctly pink in my 20 inch dob. I sense a hint of pink also in Eta Carinae.

Unfortunately, most other bright nebulae remain grey to my eyes. I am yet to see colour in the Tarantula, for example.
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  #7  
Old 17-04-2012, 07:25 PM
David Niven (David Niven)
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Shade of grey on my 20cm sct

No perception of color,just greyish hue.
At times,can be disappointing compared to those beautiful color photos that you see all to often in magazine or on the net.
After a while,reality sets in and you know that there is mo way, you are going to see the same as those photos being branded about.
I mean,when you put your eye to the eyepiece,you are not going to see much color,more likely just grey tones.
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  #8  
Old 18-04-2012, 01:02 PM
ausastronomer (John Bambury)
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Hi all,

I have seen M42 show both a greenish tinge and pink and peach tones. This is often aperture, exit pupil, observing condition and most importantly, observer dependent.

In my 18" Obsession I usually get very delicate pinks under dark skies. In my 10" and 14" scopes I usually get a slightly greenish tinge.

If you observe M42 at dusk, before full dark, it takes on a very green tinge, in all apertures over about 8". This colour perception will diminish as full darkness sets in.

In the 25" Obsessions and the 30" SDM you certainly get a perception of colour in a greater number of objects than you do in sub 20" apertures, but it is still very subtle.

Cheers,
John B
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  #9  
Old 28-04-2012, 06:48 AM
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mental4astro (Alexander)
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Here's a question along the lines of colour. Would perceived colour through a filter count? I imagine it would.

Last weekend I sent a couple of hours on M20, the Trifid Nebula, at a dark site. Using an Omega Optical OIII/Hb filter with my 17.5" dob, M20 had a definate purple colour to it. Very surprising considering purple is a colour that our eyes are not very sensitive to, and in a DSO I would have thought impossible to see. It wasn't the typical pale greenish tint seen in many bright nebulae. Very beautiful.
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  #10  
Old 28-04-2012, 07:20 PM
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Planetary nebula like NGC 3918 in Carina are great for seeing color (Herschel's Blue Planetary) . Looks intensely turquoise in a 22" at SPSP.

I believe I have seen rusty or ruddy red/pink in M42 wings with a 10" under very dark sky at zenith . To have the best chance of seeing colour you need to get the exit pupil up to 6 or 7 mm so the cones on the retina have the strongest light intensity. I agree that sunset is the best time to see the emerald colour of the trap in M42.
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  #11  
Old 28-04-2012, 07:23 PM
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Quote:
Originally Posted by mental4astro View Post
Here's a question along the lines of colour. Would perceived colour through a filter count? I imagine it would.

Last weekend I sent a couple of hours on M20, the Trifid Nebula, at a dark site. Using an Omega Optical OIII/Hb filter with my 17.5" dob, M20 had a definate purple colour to it. Very surprising considering purple is a colour that our eyes are not very sensitive to, and in a DSO I would have thought impossible to see. It wasn't the typical pale greenish tint seen in many bright nebulae. Very beautiful.
Interesting question , though I'm not sure M20 is bright enough to really see colour , let alone with a filter which will dim it a lot to a narrow band . I used to think I could see the pink half but when I looked at a photo I realised that the pink half was actually the blue in real life. So much for accurate colour perception !
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  #12  
Old 28-04-2012, 07:55 PM
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Apart from Obvious and easy to see colour in Planetaries like the Blue Planetary, the only DSO I see colour in is M42.

I see M42 as Pink and Green. I've never seen any blue in it.
To my eyes the green and pink are very obvious in my 12" Dob, and although the green is still visible in an 8" Dob the pink is really hard to see.
Dark skies really help. Any Moon light and I lose the colour in M42.

I see all other DSO's like Carina, Tarantula, etc in shades of Grey.
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  #13  
Old 29-04-2012, 10:29 AM
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I normally see the green shades in M42, and sometimes pink under dark skies when it's high. PN's do show colour reasonably well. normally NGC 3132 shows up as blue to me. As Alex mentioned, A filter really helps. just recently, I was at Bilpin, the weather was great, and the skies were dark. M57 got up, and it showed up as grey, but when I screwed on the OIII filter, it came up as blueish green with hints of red on the outside. Its a shame M57 doesn't get up very high.
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  #14  
Old 29-04-2012, 01:39 PM
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AG Hybrid (Adrian)
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The Ghost of Jupiter is bright blue, even in an 8 inch SCT
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  #15  
Old 29-04-2012, 02:10 PM
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I'm wondering if age has an effect here too. JJJ's comment might be indicative.
The first time I saw Orion's nebula was when I was 12/13yrs and using a 70mm refractor. It was very distinctly green. It continues to be green in an 8" dob and 6" refractor, though not as strong.
At the primary school star party I attended last winter I asked 5-6 people what colour they saw in Orion. The older ones said none the younger ones said green. One said blue.
It's an interesting subject.
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  #16  
Old 30-04-2012, 04:26 PM
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Sounds like my brother, he's a few years younger than me and can see blue on M42, while it only appears green to me. At a dark sky site, he sees pink and blue, while to mee it's just green with pink.
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  #17  
Old 01-05-2012, 06:26 PM
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Colors seem easier if you can compare to stars

My experience is similar to many others here. Something I noticed that seemed obvious AFTER I sorted it out is if I use my 18" and am way zoomed in on Orion I see gray. If I use a much wider field of an 8" short scope I then easily see green in Orion nebula.

Planetaries are easy to see color in generally.

So my thoughts are if you are zoomed in a very faint green is 'white balance' corrected by your brain to 'gray'. If you have a very wide field and some white stars are in the field THEN the really big nebulae look green (if a ton of OIII is present) or pink if much more Ha (really strong Ha) is present.

The surface brightness of a bright PN being maybe hotter than the faint nebula make it easier to see the OIII and thus the green or sometimes Blue.

So I try to find a few stars just outside the nebula and get my brain 'color balanced' to that color THEN swing back in over a wider field of a big nebula and maybe if your 'color correction' is slow you may see the color better.

Sometimes our brain gets in the way of seeing faint colors is the point.
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  #18  
Old 04-05-2012, 03:22 PM
ausastronomer (John Bambury)
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Quote:
Originally Posted by mental4astro View Post
Here's a question along the lines of colour. Would perceived colour through a filter count? I imagine it would.
IMO once you attach a filter, all bets re colour perception are off. The filter will impart its own unnatural colours. eg. My Astronomiks OIII filter makes just about everything look green.

Cheers,
John B
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  #19  
Old 04-05-2012, 03:59 PM
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Yes, I can see that point. One would need to qualify any colour perception according to the filter being used.

Yet, it is not like those "filtered" colours are not there in the first place. These filters transmit the very colours at which nebulae glow at, be they reflection or emission. Hb filters in the red, OIII in blue, NPB in both red & blue. The nebulae are being shown in there true state, particularly considering that at such dim levels of light our eyes see things in black and white! I'd disagree then that filters give an artificial colouration to nebulae.

For this I would then say that "bets are still ON" .

Age, individual colour sensitivity, even sex (yes, girls see colours better than boys, and colourblindness is less common in shielas too!), all weigh in too. Aperture, eyepiece coatings, seeing, all play a roll too.

I would say that whatever colour is seen, be it neat or via a filter, it is all legitimate as it is entirely at the eyepiece. Otherwise we would need to say that the colour rendition of all computer processed images are valid, when each image there is truly artificial 100%, as it wholly relies on the person behind the keyboard. I dare to have anyone disagree there!
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  #20  
Old 04-01-2014, 07:21 PM
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On a Dutch forum there is an ongoing discussion on this.

Click!

Some people even claim to see colors with 7x50 binos from downtown Antwerp which is obviously not true.
Others even claim to see red / purplish colors. I think that exit pupil is the most important factor as that determines surface brightness. A set of 7x50 binos have a better surface brightness (50/7=7.1mm) than a 75x eyepiece on a 40cm Dobson (400/75=5.3mm), but, obviously, the Dobson show much more detail as it is zoomed in more than 10 times with only slightly lower surface brightness. But the higher surface brightness would allow to see colors in bright nebulas like the Orion nebula, but also eta Carinae or the Tarantula, even with a small scope (10cm or less). But a pitch dark location is an absolute requirement so, Sydneysiders, Melbournians, sorry. I never tried it, did somebody try this with a small aperture ?
During my upcoming South Africa trip I will try it definitely.
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