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Colours of stars

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#1 25585

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Posted 03 December 2019 - 10:09 AM

As leonard suggested https://www.cloudyni...tion/?p=9337559

 

What stars of different colours, from O to R spectral classes, are good for testing eyepiece colour performance agsinst what the star should look like? 

 

Any hints for exit pupil, telescope apertures to give enough illumination, but not too much to adversely affect an eye's performance?

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  • 310px-Hertzsprung-Russel_StarData.png


#2 alnitak22

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Posted 03 December 2019 - 10:20 AM

Color vision and sensitivity varies greatly in humans. You simply must see for yourself,  and what someone else reports regarding color may have little to no relevance. I have experienced this many times when showing friends double stars. 


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#3 25585

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Posted 03 December 2019 - 10:35 AM

Color vision and sensitivity varies greatly in humans. You simply must see for yourself,  and what someone else reports regarding color may have little to no relevance. I have experienced this many times when showing friends double stars. 

Very true, but in-between, say O & B and K & M can be different from naked eye or binocular colour. As brIghtness is more intense with larger exit pupils and higher magnifications, colour subtlety can be lost. 



#4 sanbai

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Posted 03 December 2019 - 12:16 PM

For bright stars defocusing slightly may help. That can be applied to some AP too, where pin point stars saturate the sensor resulting in white color.

A high magnification can have a similar effect due to diffraction rings and/or less than perfect optics and/or haze.

The problem with high power is that turbulences and movements can be disturbing. Also if there is chromatic aberrations in the optical train or due to atmospheric dispersion.

In any case, for evaluation of color cast in the optics, I guess that a daylight use with a white target may work better. Take into account that you eyes/brain can "correct" for color cast quite quickly. Photography using manual white balance adjust may be the best.


Santiago
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#5 MitchAlsup

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Posted 03 December 2019 - 09:02 PM

At one point in time I had both a 12 NT2 and a 13 NT(1).

The 12NT2 was distinctively blue while the 13NT(1) as distinctively yellow; when viewing planets Jupiter and Saturn.

 

Most people would not notice the color difference, but one night I used only these two EPs for several hours watching the planets (20-odd years ago). I learned the color signature ofthe EP to the point where someone else could insert a random EP and I could pick it out simply from the overall color of whatever the scope was pointed at.



#6 kjkrum

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Posted 04 December 2019 - 02:32 AM

For bright stars defocusing slightly may help. That can be applied to some AP too

Quite true. This even works with a handheld DSLR and ordinary lens.



#7 turtle86

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Posted 04 December 2019 - 08:01 AM

Color vision and sensitivity varies greatly in humans. You simply must see for yourself,  and what someone else reports regarding color may have little to no relevance. I have experienced this many times when showing friends double stars.


Very true. I've noticed a similar phenomenon with planetary nebulae as well. Some people see color very well, others not so much.

#8 lylver

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Posted 04 December 2019 - 08:43 AM

Some star spectral chart

a red giant : Scheat

http://atom.lylver.o...ctro/Scheat.png

https://en.wikipedia...iki/Beta_Pegasi

 

Vega, bigger than our sun, blue-tinged

http://atom.lylver.o...pectro/Vega.jpg

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

 

Sirius, bigger also but less

http://atom.lylver.o...ctro/Sirius.png

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

 

Alpheratz, with high blue-violet emission

http://atom.lylver.o...o/Alpheratz.png

https://en.wikipedia...lpha_Andromedae


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#9 rkelley8493

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Posted 04 December 2019 - 12:47 PM

Capella is a nice subject.



#10 alnitak22

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Posted 04 December 2019 - 04:17 PM

Very true, but in-between, say O & B and K & M can be different from naked eye or binocular colour. As brIghtness is more intense with larger exit pupils and higher magnifications, colour subtlety can be lost. 

Missed this.  Hmmm....a couple of things. First, stellar brightness is constant. Secondly, larger exit pupils correspond to lower mag, not higher. 


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#11 Starman1

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Posted 04 December 2019 - 06:12 PM

Some good examples of colored stars:

http://users.compaqnet.be/doublestars/

and

https://www.skyandte...s-for-everyone/

and

https://www.skyandte...y-double-stars/

 

Many beautifully-colored double stars there.


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#12 25585

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Posted 04 December 2019 - 06:24 PM

Thanks everyone. Star colours are so beautiful, they started & keep my interest in astronomy strong! Knowing about stars also fuels my interest, so colour, type, temperature etc are all brain food to go with their eye candy views. 


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#13 dan_h

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Posted 06 December 2019 - 03:19 PM

Capella is a nice subject.

Oh yes! Then you get to see all the colors as they come and go. Delightful to watch, hard to focus. lol.gif

 

dan


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#14 clearwaterdave

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Posted 06 December 2019 - 04:36 PM

I like Sirius through my thermalpane with my cheap refractors.,it looks like a disco ball.,blinking through all the colors of the rainbow.,

  Also I practiced when learning to starhop by working my way from one k or m star to the next.,and I found that I could see the color since I knew it was there.,I'm not sure if I would have noticed their tint if I was not looking for it.,

  I like having SkySafari set on the color chart to show the stars with their tints showing.,cheers.,


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#15 25585

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Posted 08 December 2019 - 10:35 AM

This is an interesting read https://en.m.wikiped...Purkinje_effect I got the link from https://www.skyandtelescope.com/astronomy-blogs/carbon-stars-will-make-see-red1203201401/




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