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Beta Cygni and Xi Cephei

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#1 Far Star

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Posted 13 September 2019 - 07:58 AM

Two pictures I took last night with my Canon 650D, Takahashi FC-100DL and 1.8x Barlow (best single frames of many attempts; seeing was bad):

 

 

Beta Cygni (Albireo), mag. 3.4 / 5.2, sep. 34.7" (ISO 6400, 1/60 second exposure time):

 

Beta-Cygni-20190912-Takahashi-FC-100-900

 

 

 

Xi Cephei, mag. 4.5 / 6.4, sep. 8.1" (ISO 6400, 1/125 second exposure time):

 

Xi-Cephei-20190912-Takahashi-100-900-1.8

 

 

Clear Skies,

 

Ulrich


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#2 alvarete

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Posted 13 September 2019 - 08:38 AM

Xi Cephei B seems green!

#3 Far Star

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Posted 13 September 2019 - 09:58 AM

Xi Cephei B seems green!

Yes - I was very surprised, too. Sissy Haas saw it "royal-blue" whereas Rich saw it "bluish / grayisch / white" (https://www.cloudyni...sketches/page-4).



#4 flt158

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Posted 13 September 2019 - 06:12 PM

Ah yes! I remember observing Xi Cephei on 11th November 2015. 

It was very tight but a successful split at 40X. 

To check out its colours, I observed it at 112X. 

They were slight yellow and blue for me in my William Optics 158 mm apochromatic refractor. 

 

I have to say these are very stylish images, Ulrich. 

I only observed Albireo 3 nights ago. 

 

I have only ever seen 1 green star. It was not my telescope. 

It was an achromatic refractor. 

That star was the B companion of Rasalgethi (Alpha Herculis). 

 

Clear skies from Aubrey. 


Edited by flt158, 13 September 2019 - 06:14 PM.


#5 Far Star

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Posted 14 September 2019 - 02:46 AM

Hi Aubrey,

 

Star colours are naturally subjective, with opinions often varying between experienced visual observers. But the sensor of a camera is much more objective than any visual observer.

 

The above photos – taken within an hour with the same camera and the same telescope – are not just "stylish". Although the colours are somewhat "exaggerated" (I have slightly increased the colour saturation), the photos show very clearly that Beta Cygni B and Xi Cephei B belong to different spectral classes (Beta Cygni B: B8; Xi Cephei B: F8). See also this interesting picture (Source: https://en.wikipedia..._classification):

 

440px-Dwarf_Stars.png

 

Clear Skies,

Ulrich


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#6 Far Star

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Posted 16 September 2019 - 09:50 AM

This is the original photo of Xi Cephei taken with the Canon 650D. This photo has not been edited in any way. The colors of the original photo were not changed. In particular, the color saturation was not increased:

 

Xi-Cephei-20190912-Takahashi-100-900-1.8


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