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Sigma Orionis and STF 761

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#1 Far Star

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Posted 10 February 2020 - 10:50 AM

The fine quadruple star Sigma Orionis can be seen together with the triple STF 761 in a high-power eyepiece field.

 

Sigma Orionis:

 

Mag.:  AB 3.8;  C 8.8;  D 6.6;  E 6.3

Sep.:  AB/C 12";  AB/D 13";  AB/E 42"

The pair A/B is a very close binary (mag. 4.2 and 5.1) which is only separated by 0.25".

 

STF 761:

 

Mag.:  A 7.9;  B 8.4;  C 8.6

Sep.:  A/B 68";  A/C 72";  B/C 8.5"

 

Photo (single frame) taken on 02/05/2020 with 140/980 mm SD Doublet Refractor and 3.3x Barlow, ISO 800, 2 seconds exposure time:

 

7653-beschriftet-Sigma-Orionis-20200205-

 

7653-Sigma-Orionis-20200205-140-980-Refr


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#2 dmdouglass

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Posted 10 February 2020 - 12:49 PM

Excellant capture !



#3 c2m2t

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Posted 10 February 2020 - 02:11 PM

Great image!!

 

This group of systems, for me, is best viewed with a much wider field. There was a thread a few weeks ago where a number of us expressed our preference to see double stars with a bit more context or surroundings...a bit more of the stellar neighbourhood, so to speak.

 

A wider field view of this location reveals what for me is the most magnificent celestial arrowhead in the night sky. Image is attached. At the last outreach observing session I attended, I had this area centered in my 4"TMB apo having a 800 FL combined with a 20 mm eyepiece rendering about 40X magnification from a Chapters parking lot. It was breathtaking and those who observed it produced an assortment of Ooo's and Ahhh's !  The tip of the arrow is also the "H" component of Sigma Orionis, catalogued as SHJ 65AB,H. If I remember correctly, this arrowhead also dislays an orange and blue coloured component. I simply don't remember which components.

 

Cheers, Chris.

 

 

Attached Thumbnails

  • STF's 761+762-5031-ns-ID.jpg

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#4 Bonco2

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Posted 10 February 2020 - 04:33 PM

You might notice that the wide view, resembles Sagitta.
Bill

#5 c2m2t

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Posted 11 February 2020 - 12:28 PM

Hi Bill!

Your absolutely correct!!! I knew that...brain paralysis... Doh!!

Cheers, Chris.



#6 Uwe Pilz

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Posted 13 February 2020 - 11:08 AM

I observed the two multiples yesterday evening. I used my 12 inch Dobsonian at 80x. What a beautiful sight! On of teh best multiples in the sky.

Attached Thumbnails

  • sigmaOri.jpg

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#7 c2m2t

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Posted 13 February 2020 - 01:44 PM

Hi Uwe!

Great sketch! I am guessing that the colours in your sketch are representative of the stellar colours you were seeing!

 

Cheers, Chris.



#8 Uwe Pilz

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Posted 14 February 2020 - 12:18 AM

> representative of the stellar colours you were seeing!

 

Of course. Looking at the colors is part of the joy. Nearly every double has remarkable colour differences.



#9 c2m2t

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Posted 14 February 2020 - 09:15 AM

Hi Uwe!

The reason I had asked was in my earlier comment, I had mentioned that I had thought that I remember some nice colour the last time I observed this grouping but couldn't remember exactly what I had seen and what colours. Your sketch brings it all back. I remember the colours being quite vivid. In all my photographs of this area, very little if any colour is available.

 

Cheers, Chris.



#10 ssmith

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Posted 14 February 2020 - 03:54 PM

I have never seen any color when observing or photographing Sigma Ori.

 

The B-V color-indexes for all the stars are all very close to zero and trend slightly toward the blue.

 

A = -0.21

C = -0.02

D = -0.18

E = -0.08

 

2D8B0EAA-B1DE-44FE-BC50-76ECBB880E89.jpeg


Edited by ssmith, 14 February 2020 - 06:19 PM.

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