Red color and night vision

[Bertrand Laville]

Hi All,

I know the official position is to consider that human eye does not see the red color at night.

Unfortunately, or rather fortunately for me, as soon as I have a look at an emission nebula, this one becomes pink, then red, if:
- the nebula is sufficiently bright,
- I watch through the eyepiece for a long time, sometimes half an hour,
- and of course, with a filter which let pass the H aplha.

I'm sure, some of you won't believe me, but what can I do ? Here are two recent examples.

First, the Rosette nebula, through my 25" dobson, with the new filter Duo Narrowband, from Clycops Optics. I saw it in pink, because I was in a hurry. The nebula was much after the transit, and was falling down towards the horizon. So, I didn't stay a long time at the eyepiece, but I'm sure the pink would become more pregnant if I had spent more time at the eyepiece.
Secondly, Barnard's Loop, through a 4" refractor, at weak power. The filter I used is a Lumicon UHC fromm de last century, which let pass all the red.

Here are the sketches I did from these two observations, and the corresponding reports.
http://www.deepsky-drawings.com/ngc-2237/dsdlang/fr
http://www.deepsky-drawings.com/ngc-2237/dsdlang/fr

Can you tell me if some of you, guys, percieve these colors ?

Clear skies
Bertrand
http://www.deepsky-drawings.com/

NGC-2237-T635-BL-2019-03-1.jpg

Sh2-276-LC100-BL-2019-01-03-1.jpg

[wvreeven]

Occasionally I have seen a red hue in the Orion Nebula, with the central part green. Apart from that I have only seen red in stars and Mars. But that doesn't mean that it isn't possible to see red or pink in nebluae. How about the Lagoon, Eagle and Omega nebulae?

[Jimi Lowrey]

Like Wvreeven I see a pink hue in the Orion Nebula. I see lots of pink in PN but not much in emission nebula. One thing I have learned with the 48” telescope is that people see colors very differently some see lots some not so much.

[Hakann]

Like Wvreeven I see a pink hue in the Orion Nebula. I see lots of pink in PN but not much in emission nebula. One thing I have learned with the 48” telescope is that people see colors very differently some see lots some not so much.

I has a question.
When I look at M57 I see sparklining yellow.
Mel Bartels drawed it from his new 25’ and green/red.
Everyone I observed whit has never said M57 is yellow.
Issue on eye ?

[Paul Alsing]

I've seen pink in M 42 on several occasions, but the strangest red observation was while observing IC 418 while using the 82" at MacDonald Observatory in Texas in 2006. My notes read as follows...

IC 418, Lepus

This smallish PNe is said to have a red rim. When I first put eye to eyepiece this red rim was obvious, but after just a few seconds the red almost completely disappeared! If I closed my eye for several seconds, it came back for a moment or 2. Anyone have an explanation? Otherwise, this is a bright planetary with a bright CS. The interior was not exactly smooth, but not exactly detailed, either, very hard to describe. I guess that the word "mottled" works here. It seemed to me to have an overall color, but it was difficult to tell exactly what that color was... hmmm... a very curious object.

[kisspeter]

I've seen red in the Orion Nebula (the "Bar" at the edge of the Huygens Region, 16", low magnification), the nebula around Campbell's Hydrogen Star (deep red if I remember correctly, 24"), the Homunculus (orange, 24") and maybe 1-2 more small and bright deep-sky objects. But no color in larger and fainter nebulae.

I think it shouldn't be that difficult to decide if the percieved red color of the emission nebulae comes from H alpha, or something else (e.g. slightly shifted white balace in the eyes/brain). If the nebula is visible through an H-alpha filter (and no electronic enhancement and OIII and H-beta cut off) then you clearly see it. But I don't know, I've never tried to mount an H-alpha filter in ny eyepieces.

[Jason Julian]

Bertrand, you mentioned using filters in both your observations.
Do you find that filters give you better red vision than having no filter?

[Bertrand Laville]

Hi Paul,

the strangest red observation was while observing IC 418 while using the 82" at MacDonald Observatory in Texas in 2006.

You can have some explanations regarding the colors of IC 418 at:
http://www.deepsky-drawings.com/ic-0418-2017/dsdlang/fr

Bertrand
http://www.deepsky-drawings.com

[Bertrand Laville]

Hi Jason,

Bertrand, you mentioned using filters in both your observations.
Do you find that filters give you better red vision than having no filter?

Yes, obviously.
Without filter, I don't perceive any color. Of course, also, the filter must let the H alpha band pass through: if I observe the Rosette with an Astrodon OIII 5 nm, which cuts all wavelengths except 500.1 nm, I don't see any red !
See: http://www.deepsky-drawings.com/ngc-2237/dsdlang/fr

[Howard B]

Hi Bertrand,

Although there are those who refuse to acknowledge that the red color many observer's see in some of the brighter emission nebulae is real, I don't know that any of them are on this forum - but we should soon find out! I almost always see subtle shades of red in M42 and M20 without using a nebula filter.

I also think there's a difference in what people perceive between an unfiltered and filtered view of bright emission and planetary nebula. A filter that only passes red wavelengths by definition only leaves red light to see, while an unfiltered image is a combination of many wavelengths and probably dilutes the colors that are available to detect. The observer still has to have eyesight that can detect faint color, which not everyone can do. I think most observers, including myself, don't use filters to detect colors in nebulae, but it's certainly a direct and valid way to go about it.

Although I think the observers on this forum are too experienced to be unaware of the potential of seeing what they expect to see, there is a bias created by the color images we see everywhere that we have to account for when observing colors in these nebulae, and is always worth mentioning to those with less experience. On the other hand, young children almost always see lots of color in M57 without being familiar of its photographic appearance, while the best I can do is see a warm hue around its circumference!

[Hakann]

The only color I seen is the yellowish in homunuculus and the pink/yellow in Tuc 47.
M42 its more the normal deep sky, maye to tiny green at the best.
But how do people see the M57, all I observe whit said its not yellow inside, but for me it is. Strange.

[Bruce Sokol]

I've seen reddish or pale pink in M 42 many times as well as green in the brighter areas with an 18' Dob with no filter. M20 has looked pinkish on some nights as well. I'll have to see if my old Lumicon UHC brings out more color, I usually don't use a filter on M42.

Last winter I saw the Rosette Neb. with a 6" F4.8 Mak-Newt at 24x with a 3 degree field using the NBP filter, and it looked very slightly pale pinkish.

[PeterN]

From a dark site, I can see a warm pinkish tone in NGC 40. Not too many PN's that exhibit a warm coloration. My past 24" Dob showed it well.

NGC40_Mandel_Block_NOAO.jpg