Color detection in double stars

[terrynak]

5-17-20

Brought out the 50mm F/12 Tasco 66TE for some more double star work.

• 95 Her (Her; mag.=5.0, 5.1; sep.=6.3”) – star hopped from Zeta Hercules to get here; able to split cleanly using 67x. James Muirden called it “ a magnificent pair, appearing yellow and white”. Was able to see the yellow hue in the primary.

Unfortunately, the clouds moved in as I was wrapping up observations on this double and had to abort.

5-18-20

Same scope as last night.

• 100 Her (Her; mag.=5.8, 5.8; sep.=14.2”) – whitish pair.

• 40, 41 Dra (Dra; mag.=5.7, 6.1; sep.=19.3”) – able to split at 24x; using 67x, can see the yellow/white contrast of the pair.

• Psi Dra (Dra; mag.=4.9, 6.1; sep.=30.3”) – easy at 24x; at 67x, can see the contrast between the yellow of the primary and white of the secondary although James Muirden says the latter is purple.

• Nu Dra (Dra; mag.=4.9, 4.9; sep.=62”) – very wide pair; supposed to be both yellow, but couldn’t tell.

I'm becoming more interested in determining color in double stars. Easy to do, especially when your scope delivers sharp star images.

[notFritzArgelander]

Detecting color is an interesting but highly subjective enterprise......

I confess I am a sucker for color in observing. But I don't exactly take my color perceptions as factual or physical. Take the color purple, for instance.... Nice to see, but its in the eye of the beholder.

[terrynak]

I'm new to the game of detecting color in stars. Was intrigued when James Muirden (Astronomy with a Small Telescope, 1985) said Psi Draco was "yellow and purple; a beautiful pair". Guess I'll need to point a bigger telescope at it and see if I can detect the purple...

Interesting that I would get into double star color observing with the first scope I ever bought (40 yrs ago). It's more fun to detect color in stars when you see them as pinpoint sharp Airy disks. Although I first became intrigued by color when I ran into carbon stars during the course of my asterism observing years (2016-2018) using mainly reflectors.

[John Baars]

Thanks for your nice report. I like the instrument!
Observing colored stars has always been my sort of weak point. The brightest ones, ok. But the red stars in the Perseus double cluster for instance.. pff....with the utmost trouble. I more or less envy those who see differences in a wink.
Well done!

[notFritzArgelander]

I'm new to the game of detecting color in stars. Was intrigued when James Muirden (Astronomy with a Small Telescope, 1985) said Psi Draco was "yellow and purple; a beautiful pair". Guess I'll need to point a bigger telescope at it and see if I can detect the purple...

Interesting that I would get into double star color observing with the first scope I ever bought (40 yrs ago). It's more fun to detect color in stars when you see them as pinpoint sharp Airy disks. Although I first became intrigued by color when I ran into carbon stars during the course of my asterism observing years (2016-2018) using mainly reflectors.

Well, larger aperture intensifies color that is to be sure. The stunning thing about observing with a 1 meter scope is that enough light enters the eye so that the colors are easy to see.

But to see purple as Muirden sees you'd need both his instrument and his eyes. Don't be disappointed if you can't reproduce someone else's color observation. That is SO dependent on the Mark I eyeball that it's best to just enjoy the colors that you see.

[Bigzmey]

Nice catches Terry!

All components of the optical train - from scope optics, to diagonal, to EPs to observer eye - can affect how the star color is perceived.

Atmospheric conditions, scope aperture and exit pupil will also affect hue and saturation.

I split doubles with variety of instruments from 10x50 binos to 8" SCT. Looking at my notes, the color of the same star can range from red to pale orange.

I find star colors wonderfully subjective. Some say there are no green or purple stars. I say report what you see. After keeping the records for a while you would realize that white stars next to orange may appear greenish and bluish star lower to the horizon - purple. There is perfectly good physiological/physical explanation for these mixed colors.

[terrynak]

Thanks nFA, John, and Andrey for your comments on how to see color in double stars (and stars in general).

I'm just going to report what I see based on scope aperture, EPs used, and possibly height of the double above the horizon. Especially trying different EPs to see if it makes any difference in hue.