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Observing >> Double Star Observing

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JIMZ7
Pooh-Bah
*****

Reged: 10/22/05

Loc: S.E.Michigan near DTW
Cor Caroli
      #5928280 - 06/18/13 09:18 PM

A very nice colorful double at magnitude 2.9 & 5.6 & 19.6" separation in Canes Venatici. I said this once before in a different post with 4" refractors that the colors were a blue primary & green secondary. Now with my 10" f/5.6 Dob the secondary at 47x still remains a olive green. I can't be the only one still seeing this--am I?

Jim


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fred1871
scholastic sledgehammer


Reged: 03/22/09

Loc: Australia
Re: Cor Caroli new [Re: JIMZ7]
      #5928435 - 06/18/13 11:32 PM

A lovely double - but there's not a lot of agreement on the exact tones of the colours.

Flammarion (19th century) called them "golden yellow and lilac"; Sissy Haas in her book has "white and bluish sea green" with a 60mm refractor; she quotes TW Webb with "Pale yellow; pale copper". I looked at it with a 7-inch apo refractor (AP) and saw "white and orange". On the other hand, I see the companion of Antares as definitely "green", so green is a colour I sometimes see in stars.

Apparently, not everyone sees a colour contrast here. Hartung calls the stars "pale yellow". Burnham, in the Celestial Handbook, remarks on this failure to see colour contrast, mentioning that TW Webb said John Herschel saw no colour contrast.

Burnham also quotes RH Allen - "flushed white and pale lilac"; Agnes Clerke "pale yellow and fawn"; so not a high difference there. Baron Dembowski called the fainter star "pale olive blue" - odd, says Burnham, who prefers Webb's "pale copper" because it agrees with the spectral type (F0).

It might come down to choosing your colour preference (or your eyes doing it for you).


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David Knisely
Postmaster
*****

Reged: 04/19/04

Loc: southeastern Nebraska
Re: Cor Caroli new [Re: JIMZ7]
      #5928512 - 06/19/13 12:27 AM

Nope, in my 10 inch, the two have only a very mild color contrast. I see a bluish white and cream color to the two stars (no "green"). The primary is an A0 star similar in color to Vega while the companion is class F0 (basically white). They are pretty, but no green here. If you want to see green, I might suggest some of the brighter planetary nebulae, as they can appear a very nice bluish-green color when viewed directly at low powers. Clear skies to you.

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Nucleophile
super member


Reged: 05/24/13

Loc: United States
Re: Cor Caroli new [Re: JIMZ7]
      #5928620 - 06/19/13 02:23 AM Attachment (19 downloads)

I have always found this double to be a delight.

It does appears slightly greenish to me in my 8 inch reflector--as the attached photo through this instrument suggests.


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Nucleophile
super member


Reged: 05/24/13

Loc: United States
Re: Cor Caroli new [Re: JIMZ7]
      #5928621 - 06/19/13 02:24 AM Attachment (18 downloads)

.....but through my 15 inch reflector the greenish colored is nearly gone. Here is a recent photo through that instrument.

Edited by Nucleophile (06/19/13 02:26 AM)


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ClearSkies.eu
Vendor (Clear Skies)


Reged: 05/07/07

Loc: the Netherlands
Re: Cor Caroli new [Re: Nucleophile]
      #5928709 - 06/19/13 06:15 AM

A always appeared white to me, while B was yellow(ish) in an 8" SCT and light blue in a 12".

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Rich (RLTYS)Moderator
Postmaster
*****

Reged: 12/18/04

Loc: New York (Long Island)
Re: Cor Caroli new [Re: JIMZ7]
      #5928712 - 06/19/13 06:18 AM

In my 10" scope I'd describe both stars as bluish white.

Rich (RLTYS)


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Silver Bear
member


Reged: 04/02/13

Loc: Brazos Valley in Texas
Re: Cor Caroli new [Re: ClearSkies.eu]
      #5936756 - 06/23/13 05:02 PM

Quote:

A always appeared white to me, while B was yellow(ish) in an 8" SCT and light blue in a 12".




That's how it appeared in my telescope when I split this double 6 weeks ago - a white primary with a yellowish companion. A week later, when I split the double a second time, the primary was still white, but the companion also appeared white.


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JIMZ7
Pooh-Bah
*****

Reged: 10/22/05

Loc: S.E.Michigan near DTW
Re: Cor Caroli new [Re: Rich (RLTYS)]
      #5952646 - 07/03/13 07:58 AM

I guess it depends what power you use,because at 202x both stars appear to be bluish/white in my 10" Dob. At 47x the secondary star to me still shows a "olive green" tone.

Jim


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