Low-light colour blindness?

[Mr Spock]

46 minutes ago, Stu said:

This is the full test, I think the one above is mean to show nothing if you are not colour blind…

https://www.challengetb.org/publications/tools/country/Ishihara_Tests.pdf

Passed that test easily enough.

I can see star colours well enough. To me Arcturus, Aldebaran and Betelgeuse are all orangey red, much like Mars. Blue stars are more difficult and appear a 'cleaner white' if that makes sense.

I've not seen colour in nebulae, even with large scopes.

[Carbon Brush]

@JOC This brings to mind two events.

The first was a story from my mother.
As a child (1930s with far less light pollution) she travelled in a car at night, which was of course a novelty.
When the headlights showed the verges, they were green. Until then all of her night vision away from buildings had been monochrome.

My observation when first trying out a DSLR for astrophotography. I took a time exposure on the back lawn.
Green to the camera, but monochrome to me.

Of course a really good illustration of the variety star colours is a wide angle photo. Exposure seconds to tens of scends. Whether tracked or the onset of star trails.

David.

 

[PeterW]

The colour disc arrangement test, like this one or larger ones are more detailed in their diagnosis…. https://www.color-blindness.com/color-arrangement-test/
 

peter

[Kon]

@JOC gave a very good explanation and in addition, Retina with age declines and colour perception decreases especially at low light.

I similarly see Aldebaran and Betelgeuse dark orange/ reddish. The double cluster in Persei show some dark yellows/orange. Regarding M42 I have seen reds,pinks and teal green when transparency is extremely good. Very subtle no AP colours. It mostly appears greenish/grey in so-so nights. Light pollution and transparency will affect colours.

 

[ScouseSpaceCadet]

Strange... Despite being red/green colour blind, massively reducing career choices when younger, I can see the colour in stars. The wide field of binoculars spectacularly enhances the effect. The colours may not be correct colours but I can definitely see them! 

The familiar red giants look orangey-red. Blue stars are more white with a pale blue hue. When behind the telescope splitting coloured doubles, I can see the colour difference but as above, occasionally I'm not sure if the identified colour is correct.

Regarding M42; when I owned an 8" dob I did on at least a couple of occasions observe a green hue.

 

[Stu]

I used to think I didn’t see much colour through a scope, particularly on Jupiter. I notice colour in stars with the naked eye, and Mars for instance, but when I first started observing Jupiter I just didn’t register the colours.

Over the years I’ve obviously trained myself to see them, because now I do see a full range of colours from pastel shades to the orange or brick red in GRS. This is helped actually by not being too well dark adapted so that your cones are still triggering, same for the planets too. It’s a good idea to look at a bright light every now and then to keep your eyes unadapted.

I also now see greenish tints to the Orion nebulae in scopes as small as 4”, again helped by a lack of dark adaptation. For dimmer objects you definitely need darker skies and a big aperture to be seeing colours.

[cajen2]

Reminds me irresistibly of a book called "The Art of Coarse Cruising." When the author was sailing across the Channel, he saw a ship. He called to his colourblind friend, "What colour light is that ship showing?"

His friend thought a while.... "Brown."

Edited January 23, 2022 by cajen2

[wulfrun]

Actually, most people who believe they are colour-blind are mistaken. Colour blindness is extremely rare...but colour *deficiency* is not, it's relatively common. Red-green deficiency is the more common variant. To be colour-blind you need to have either 2 or all 3 of the cone-cell types missing.

In low light, the cones in the eye may not be triggered. Cones provide detail and colour information, so in poor light we lack visual acuity and colour perception.

The Ishihara colour test isn't usually used where critical colour vision is needed, it produces too many false positive and false negative results. The more critical test is the Farnsworth-Munsell 100-hue test. I used to be a colour-matcher and had to do it every 6 months or so.

With stars, I see the colours easily enough in a telescope but without optical aid I struggle to tell blue from white unless they're very bright. The redder end of things can also look white if they're lower brightness too. I've never seen colour in nebulae but I've never looked through a huge-aperture scope either.

[Carbon Brush]

Ref @ScouseSpaceCadet.
I work with someone who describes himself as red/green colourblind.
In summer, poppies in the hedgrows near work are all but invisible. As is a 'proper' red phone box against a privet hedge.
Mixing traffic lights and orange (low pressure sodium) street lights was a problem when driving.
But when the army hide something under camouflage netting in the bushes, he can see it and I can't!

[PeterW]

I have relatives who are green sensor blind, so not anomalous red-green. 
 

peter

[Pixies]

I remember my teenage son coming out from the kitchen one night, with no dark adaption - looking through my dob at M42 and saying, "Cool! Pink and green!".

I had been observing it as grey for over an hour!

 

Also, with Neowise last year, he could spot it straight-off in a summer night sky, when I needed to scan with binos to find it.

 

[F15Rules]

I'm not colour blind at all, but I could well believe that as I get older my all round visual acuity is lessening gradually.

With visual astronomy, I've always found most star colour differences to be very subtle..with the exception of reddish stars such as Betelgeuse, Arcturus, Aldebaran etc which have always been very clearly reddish/orange.

When I read my "Double Stars for Small Telescopes" by Sissy Haas, a book I genuinely really like, I do find that the description of colours and hues in the notes/comments sections, often made by historical observers from the 19th century, are, frankly, ridiculous and fanciful, especially when for example they might describe a faint companion, which is several magnitudes dimmer than it's much brighter primary, as being "emerald green" or "topaz"..I do think that Victorian observers in particular took real license in their extravagant "coloured stars" descriptions!😇😋...perhaps they were colour blind?

Dave

[Sunshine]

My neighbor says he’s color blind and can’t see the red or green, he can tell when they’re lit up and knows to stop or go based on which light is lit in the pattern lol. When he was explaining this it took restraint not to ask if the ministry of motor vehicles knows this lol.
 
What would happen if he found himself driving where the street light pattern isn’t the same as is common here? Does anyone else have this same issue? it must have been difficult when first driving a car but I’m sure one adapts quickly.

Edited January 25, 2022 by Sunshine

[mikeDnight]

I seem to see reds and yellows very easily. If you look at the cross of Cygnus, the upper right quadrant, if I can call it that, there is a visual triple star affectionately named The Patriotic Triple. Its Red, White & Blue, and quite widely spread and so needs a low power wide field. I do find the most distinctive colours appear when studying double stars. Higher powers help with contrasting doubles, as does defocusing the star slightly. I would imagine most people could see the contrasting colours in Beta Cygni, which to me are turquoise and gold. The green pearlescant glow of the Orion nebula is something I see virtually every time I observe it, but it wasn't always that way. It took time for me to learn to see what I see with relative ease today, so I never assume a fellow observer is seeing exactly what I'm seeing.

Edited January 25, 2022 by mikeDnight

[ollypenrice]

On 23/01/2022 at 18:14, Dave scutt said:

I have problems seeing any colour's too.

If you can't see the number in the image like me your coloured blind. 

It might be worth checking your source for this particular Ishihara test. I've just done a 12-sample Ishihara test online and, as usual, saw every figure. I'm certainly not colour blind but, in this, I can't see a letter or number so I think it tests for something else.  There are control tests with nothing in them and also tests in which only a colour blind person will distinguish a figure.

On 23/01/2022 at 17:54, cajen2 said:

Am I the only one with this problem?

I keep reading (here and in books) about stars which are deep blood red, dazzling blue, etc. I also note some people say they can see reds and greens in M42, for example. I'm not talking about long-exposure images here, but I can't see any of these colours - everything looks white to me. I tried to persuade myself that Aldebaran, for instance, was really orange-red but I'm not convinced. This seems to be true at any magnification too.

In normal light, I'm not colour blind or have any trouble distinguishing colours. Is there a condition like mine at low light?

A good while ago I took UCLAN's Introduction to Astronomy distance learning course.  One of the tasks was to rank ten naked eye stars from red to blue. I was surprised to find I got the order right (ie in accordance with spectral class) apart from inverting one adjacent pair near the middle.  This makes me think that your vision may have a limitation but, to be sure, I'd go to a dark site with a few other people who know the sky well enough to be sure you were all talking about the same star!

Very big apertures are not the best for star colour in my experience. A reflector is the most reliable on colour and being out of focus slightly helps to spread the colour and diminish the brightness.

Olly

Edit: Sorry, I missed the later posts and the test problem has already been resolved.

Edited January 27, 2022 by ollypenrice

[DaveS]

On 23/01/2022 at 20:24, PeterW said:

The colour disc arrangement test, like this one or larger ones are more detailed in their diagnosis…. https://www.color-blindness.com/color-arrangement-test/
 

peter

Tried that test and apparently I'm Not colour Blind, confirming the ishihara tests I've done in the past.