31 replies to this topic

[northbynortheast]

I was watching a presentation last night at my local astronomy society and there was some discussion of stars' colors. Is there a best practice or best binocular for observing the blues and reds and oranges and whites? I've even read that some binoculars can bring out a deep, luxurious blue in the background sky. I'm afraid I don't know if it comes down to types of glass or magnification or design--or if it's just specific to individual binoculars, for example ones that lean warm in tone, etc.

 

Van Gogh was seeing (or imagining) all kinds of colors in his starry night, and I'd like to do some color hunting myself.

 

Thanks! 

 

--Nat

[Corcaroli78]

Hi,
I noticed that star colors were more evident when i looked through an old Zeiss 10x50 than newer porro models from other brands like meade or Celestron. At that time, the old Zeiss was a reference for the sparkling views among the club members. I do not know why, but it could be a combination of glass formulation. exit pupil and aperture. Curiously, my Vortex and BA8 10x50 do not show saturated colors.

[Fiske]

Ironically, star colors of brighter stars are more apparent in urban skies due to the reduced contrast with the background sky. 

[jrazz]

Oohhh. Physics! My favorite subject: https://www.scientif...ars-explained1/

 

But to your question, a number of factors can enhance perceived star color: sky conditions, brightness of star, brightness or transparency of instrument and contrast. I’ve found that the latter makes the most difference. The better designed, baffled, and darkened an instrument is the more color you see. How stable your mount can make a big difference too.

 

Finally, there is the observer. Some things you can control like how dark adapted you are. Blocking out stray light helps immensely. Altitude also matters. Less air pressure means less oxygen for your eyes. Other factors you really can’t control. Genetics, eye health and general fitness make a difference. Gender also has a surprisingly large effect on color perception with the estrogen inclined populace generally having better color perception.

 

Finally there’s experience. How steady you are and how finely tuned can also affect your color perception. One thing to remember is that the cones are more densely packed in the center of you vision. That’s why you see color in direct vision but not averted. The effect can be startling, I’ve found, especially in planetary nebula where they can have amazing color in direct vision but blink into white as soon as you move your gaze. Really fun to try.

 

 I personally think that star color is fun and beautiful as well as really interesting scientifically.

[northbynortheast]

Thanks, all. And WOW, Jordan--that's a fantastic answer (and link). I can't say that physics is my favorite subject but your explanation is clear and ... inspiring!

 

Edit: I love this: "That’s why you see color in direct vision but not averted. The effect can be startling, I’ve found, especially in planetary nebula where they can have amazing color in direct vision but blink into white as soon as you move your gaze. Really fun to try."

 

Some people "learn something new every day." I learn many new things every night, thanks to this forum.

Edited by northbynortheast, 12 September 2023 - 11:27 AM.

[Scott99]

Bigger aperture makes star and planet colors more apparent IMO, go with big lenses to bring out the colors. 

[Terra Nova]

For the best discernment of true colors in stars, the three biggest factors IMHO are aperture, ED glass, and the best modern coatings. Type of glass, coatings, and the figure and polish of that glass will reduce or eliminate any introduction of false color caused by the optics themselves. Since we need our cone receptors to distinguish color and they don’t work nearly as well in low light as do the rod cells, we need all the light collection we can get. That increases to the square of the instrument’s aperture. Ie. 70mm binoculars collect 4 times as much light as 35mm binoculars. That’s what I love about my Oberwerk 20X70 ED Ultras. They do a wonderful job in showing the stars in their multiplicities of natural colors and brightnesses.

Edited by Terra Nova, 12 September 2023 - 12:07 PM.

[Astronoob76]

Bigger aperture makes star and planet colors more apparent IMO, go with big lenses to bring out the colors. 

Seconded. One of my best binos in that regard is an old AK-prism 9x63. Too bad that size fell out of favour with hunters since the advent of affordable nightvision equipment. In the past, every big maker had a good 9x63 in the line-up. Now they became rare as hen's teeth.

But an 8x56 or 7x50 might also work. A 10x70 too. Large exit pupil and large aperture are the biggest factors. I'm still on the lookout every now and then for the last 9x63 generation made by Optolyth with AK-prisms and relatively modern coatings "Ceralin+" they called it. Too bad that Optolyth went belly-up during Covid. They were the last European maker to have a 9x63.

[Fiske]

For fainter stars, additional aperture and magnification certainly makes a difference. Plus the quality of the optics and coatings. But for brighter stars, I'm not sure that colors aren't more apparent with lower magnification/smaller aperture instruments rather than higher magnification/larger aperture. Seems like some side by side comparisons might be in order here. 

Edited by Fiske, 12 September 2023 - 12:55 PM.

[Dale Smith]

Fantastic thread! Star colors are one of the highlights of the night sky for me. Terrific explanation by Jordan, and some great additional comments by everyone.

 

FWIW, I’ve noticed vivid star colors at 6.5x32=specifically the Kowa BD II and the MoonStar. The Vixen Astro does well here, too. 

 

As far as aperture goes, the 10.5x70 Resolux also shows vivid star colors. Terra’s comment about the 20x70 ED Ultra has me thinking about that binocular again.

[Erik Bakker]

The better quality a binocular is and the bigger the aperture, the more easily they will show star colors under any given sky.

 

All my 42-70mm binoculars show great star colors. I particularly enjoy how they show the subtle shades of red and oranges in red giants, or pairs of red/orange and blue stars. And yes, they are all high quality instruments.

[DeanD]

Further to Jordan's reply, I wonder if any research has been done about the effect of colour-blindness on perception of star colours? They tell me that around 1 in 12 males are colour blind to some extent, but only 1 in 200 females...

 

For example, my Dad was seriously colour-blind, only being able to see blue as a distinct colour. He didn't really like indoor plants, because for him they were effectively varying shades of brown. He would have had major problems seeing, for example, Mars or Antares, Betelgeuse, etc. as "red"- and certainly wouldn't have been able to enjoy Alberio. Fortunately that particular gene didn't affect me.

 

It might be worth checking out if you have problems seeing star colours: there are lots of tests online to give you some idea.

 

- Dean

[sevenofnine]

+1 on Terra's post...She explains exactly what I see using the Oberwerk 20x70EDU. I could not agree more 

[binocular]

For the best discernment of true colors in stars, the three biggest factors IMHO are aperture, ED glass, and the best modern coatings. Type of glass, coatings, and the figure and polish of that glass will reduce or eliminate any introduction of false color caused by the optics themselves. Since we need our cone receptors to distinguish color and they don’t work nearly as well in low light as do the rod cells, we need all the light collection we can get. That increases to the square of the instrument’s aperture. Ie. 70mm binoculars collect 4 times as much light as 35mm binoculars. That’s what I love about my Oberwerk 20X70 ED Ultras. They do a wonderful job in showing the stars in their multiplicities of natural colors and brightnesses.

Still new at stargazing but are the stars still tiny pin sized dots through your 20x70 when compared to a 10x50? 

Edited by binocular, 13 September 2023 - 11:29 PM.

[gwd]

I had a naive personal observing program around star colors.  I kept notes etc.  Then I moved to darker skies and compared my observations.  I couldn't replicate my observations in the new location.   Dark adaptation seems to mean that your color preceptors (cones) shut down or the rods output overwhelms them.   It seems to be more of a physiology/ pscychology subject than physics.   My naive program was to try to map my perceptions to spectral type but there seem to be too many confounding variables.

[Fiske]

I had a naive personal observing program around star colors.  I kept notes etc.  Then I moved to darker skies and compared my observations.  I couldn't replicate my observations in the new location.   Dark adaptation seems to mean that your color preceptors (cones) shut down or the rods output overwhelms them.   It seems to be more of a physiology/ psychology subject than physics.   My naive program was to try to map my perceptions to spectral type but there seem to be too many confounding variables.

George,

 

I do see star colors consistent with stellar spectral types to a certain extent. But reading your post, now I'm wondering if that is because my eyes aren't fully dark adapted observing from my yard.  Which I think might be closer to the truth than otherwise.

 

Here is a quote from my ExploreTheNightSky blog post about the double star STTA 206 in Cygnus, the B component of which has created an infrared bow shock due to its large mass and high-velocity.

 

B spectral type stars typically have blue-white color indexes, but toward the end of their lives radiation from the core causes the outer envelope of the star to expand and cool, resulting in different color indexes. In the case of HD 229159 the result is an orange star, seen as deep yellow compared with the white color of the A component in my observation notes.

Just as you report, I have always found stellar colors more apparent in urban skies than in darker skies, attributing the difference to contrast between the stars and the background sky. A way to test this would be to observe from a darker site, observing a set of stars fully dark adapted and then look at a white light to reduce dark adaptation (in such a way as not to disturb other observers if present) and reobserve the same set of stars.

Edited by Fiske, 14 September 2023 - 07:54 AM.

[gwd]

I liked this web article about star colors so much I downloaded it into my folder for my naive project.  I should have read it before I began.

https://southastrode...29bAmerican.htm

 

We exaggerate minute differences in our minds, why do we enjoy close double stars with contrasting colors?  Find isolated stars with the identical spectral types and magnitudes of the components  of Albireo and see what color you see.   I sometimes see a component of a close double as an impossible color like green. 

[GlennLeDrew]

Sensing color occurs in the photopic regime, meaning dark adaption is not required. Indeed, I find it to be counterproductive. As the night progresses during an observing session, I find star colors to continually become paler, as though 'washed out.' I ascribe this to the process of photochemical processes in the retina as dark adaption progresses. A blast of white cures this, for then star colors are instantly rendered more saturated.

 

Needless to say, this is not recommended if hunting down fainter nebulae is also on the menu. But if the session is dedicated to appreciating star colors, then occasional exposure to bright light is actually a good thing.

 

An excellent start on this journey is furnished by the brighter carbon stars. Most vary considerably in brightness (due to being red giants near their end of life before becoming a planetary nebula), and so at the time of observation your target could be dim or invisible. But track down a few and chances are at least one will be near maximum brightness and thus reveal its deep ruddy hue in a 10X50.

 

Another neat exercise to try, involving no optical aid. Take a small mirror outside and contrive to orient it so that an otherwise isolated bright star is brought close to another bright star. In the Spring sky, Arcturus and Spica are a good pair, or a bit later when Scorpius has risen, Antares and Spica. Arcturus and Antares already evince a golden and orange-ish hue, respectively. Spica, on the other hand, and like the hot, blue stars in general, has a very subtle hue that tends to look neutral white to most. But in this close placement arrangement, the color contrast with the ruddier star brings out the blue rather prominently. Not unlike the orange-blue pair of the famous colorful double star, Alberto (an excellent exhibition of star colors for bino users in its own right.)

[KBHornblower]

I find Albireo's colors more vivid in a small aperture, say 50mm, than in a much larger one.  The small one puts the stars in the sweet spot for seeing pastel colors of point sources, while the colors become washed out at brighter levels.  If too bright, the stars saturate the few receptors they are exciting.

[gwd]

In post number 18 of this thread: "A blast of white cures this, for then star colors are instantly rendered more saturated." and 

"But in this close placement arrangement, the color contrast with the ruddier star brings out the blue rather prominently" imply there are two different mechanisms- a photochemical process that occurs in each individual retinal cone cell and some other neural process that occurs further along when our minds construct an image or mental impression from the excitations of several retinal cells.  Otherwise the blue and orange stars would appear to be the same color when viewed separately or together.    

 

This complex subject has practical implications for stargazers.  We who operate under light polluted skies can develop our personal star-hops with star color as a maker.  If we communicate the color based star hop to a fellow (through cloudy nights perhaps) who observes fully dark adapted he or she may find the instructions useless without a bright moon present.   

[aznuge]

I was watching a presentation last night at my local astronomy society and there was some discussion of stars' colors. Is there a best practice or best binocular for observing the blues and reds and oranges and whites? I've even read that some binoculars can bring out a deep, luxurious blue in the background sky. I'm afraid I don't know if it comes down to types of glass or magnification or design--or if it's just specific to individual binoculars, for example ones that lean warm in tone, etc.

 

Van Gogh was seeing (or imagining) all kinds of colors in his starry night, and I'd like to do some color hunting myself.

 

Thanks! 

 

--Nat

Van Gogh's other Starry Night - Starry Night over the Rhone is equally captivating in its color and placement of the Great Bear.  He painted it in Arles, France in September 1888.  I checked with Stellarium and found this star map from Arles, France from late Sept 1888 that depicts the big dipper in about the same position to the horizon as Vincent painted it.

 

Star background from Stellarium; Arles, France, Sep 1888

 

I can't help thinking about this since it came up in an Asterism post over a year ago.  Last year my wife and I were traveling in Greece and Italy in late Sep/ October. We had some great views of the Great Bear from our location on Santorini, in the position just above the horizon - unforgettable.  Unfortunately we cannot see this constellation in the same position from our back yard this time of year due to obstruction by hills, and the overwhelming city glow to the North.

 

But back to Van Gogh, stars, and color:  In this particular painting (shown below) the artist is reported here to have indicated some details about the color in it to his brother Theo:

 

“The sky is aquamarine, the water is royal blue, the ground is mauve.” He continues, “The town is blue and purple. The gas is yellow and the reflections are russet gold descending down to green-bronze.”

 

And more interesting to me is Van Gogh's caparison of brightness and color between the stars of the big dipper and the gas lights of the city, reference here:

 

"On the aquamarine field of the sky the Great Bear is a sparkling green and pink, whose discreet paleness contrasts with the brutal gold of the gas. Two colorful figurines of lovers in the foreground."

 

Starry Night over the Rhone - Vincent Van Gogh

 

I am very much on the learning curve in discerning star colors and in taking in all the variables involved - aperture, manufacturer, conditions, power, star magnitude, etc.  But it is always exciting when those conditions converge and the brilliance of color shines through.

Edited by aznuge, 19 September 2023 - 09:51 PM.

[northbynortheast]

That's a lovely post, @aznuge. Thank you for taking the time to write it.

[CarolinaBanker]

I’m currently reading Colours of the Stars: https://www.amazon.c...n/dp/052125714X

 

You may find it to be of interest to you.

[Terra Nova]

I had a naive personal observing program around star colors.  I kept notes etc.  Then I moved to darker skies and compared my observations.  I couldn't replicate my observations in the new location.   Dark adaptation seems to mean that your color preceptors (cones) shut down or the rods output overwhelms them.   It seems to be more of a physiology/ pscychology subject than physics.   My naive program was to try to map my perceptions to spectral type but there seem to be too many confounding variables.

The cones don’t shut down, they are still operating. They (the cones) are in fact, the retinal cells most responsible for visual acuity. Without them you wouldn’t see fine detail sharply. Thus, if they were shut down, inoperable, or non-existent, it’s doubtful you would be able to split double stars, let alone differentiate their individual colors. This is why the rarest form of color blindness, achromatopsia, also known as rod monochromacy, a very rare congenital genetic disease or birth defect (autosomal recessive trait) where individuals are born without cone cells, is such severe visual disability. It’s just that the cones are far weaker photo receptors than the rods.

[KBHornblower]

I find Albireo's colors more vivid in a small aperture, say 50mm, than in a much larger one.  The small one puts the stars in the sweet spot for seeing pastel colors of point sources, while the colors become washed out at brighter levels.  If too bright, the stars saturate the few receptors they are exciting.

Last night I looked at Albireo with my 15x50 binoculars.  As is often the case, the closeness made the colors, especially the blue of the fainter star, appear more vivid than they would have if widely separated.  I perceived it as a striking sapphire color.