Struve 761 

Craig M. Carver
Star: Struve 761 
Date & Time:  November 29, 1998 0300 UT 
Seeing:  6 <1-10 Seeing Scale (10 best)> 
Location of site: Randleman, NC  (Lat 36.07, Long 79.79, Elev. 500 ft) 
Site classification: Rural 
Sky darkness: 5.4  <Limiting magnitude> 
Telescope: 6" Maksutov 
Magnification: 95x 		 This is in the same field of view (0.7 degrees) as Sigma.  There are three easily visible stars all about the same magnitude, approximately 8.0.  Two of the 
stars are white and are about 8 seconds apart from each other at a PA of about 270.  The third star is very pale blue and is about a minute from the nearer of 
the pair with about 25 degree PA (or in other words, the nearer of the pair is at about PA 205 from the distant star). 

 
Dominik Elsässer
Star: Struve 761 
Date: Dec. 30 1998; 23.00-23.30 UT 
Seeing: 2 
Limiting Magnitude: ~3.5 (moonlight) 
Location: Kleinkahl, Germany 
Site Classification: Rural 
Telescope: Vixen 102M 
Magnification: 100x 		 Due to the poor seeing and the bright moonlight only two stars  (separated 1.2 arcmin and 9"; magnitudes ~8) of this quintuple system could be observed. 
However, since Struve has only the two stars at 1.2' in his catalogue, I consider this observation successfull in terms of the "Orion 33" project. Nevertheless, I'll try and hope to observe the other stars under better conditions! 

[Updated from the "33 in Orion" forum]: Since Dec. 30 1998, I've done some science in this system. According to my catalogues, Struve 761 consists of no less than five stars!. These are: 

A1: GSC 47711139 at ra 05h 38m 36.5s mag 7.89 
dec -02° 33' 12.8" 
A2: GSC 47711138; Separation(A1): 35" at PA 128° mag 12.4 
B1: GSC 477112051; Separation(A1): 1.2' at PA 206° mag 8.43 
B2: GSC 47711133; Separation(B1): 5.5" at PA 261° mag 7.7 
B3: GSC 477112041; Separation(B1): 8.7" at PA 267° mag 8.62 

[Annotation: I made the "classification" (A1,B1...) for better orientation. This is in no way correlated to the "official" names of the stars (e.g. from WDS)!]. So, I think I observed the stars A1, B1 and B3 on Dec. 30th. 

[Updated from the "33 in Orion" forum (1/7/99)]: I just revisited Struve 761 under very good conditions (seeing ~1" and Sky Darkness ~6) on Jan.06.99 at 20.30-20.50 UT. This time I could find all five components, including the mag. 12.5 star, which was a lot easier to see than I had thought!. Together with the yellow component in Sigma, this "Big Arrow" in my opinion is surelly one of the most beautiful stars on the "33" list. 
 

 
Chuck Layton
Star: Struve 761 
Date of Observation: Jan. 11, 1999 
Time of Observation:  0430 UT 
Seeing (1 - 10, 10 best):  5 
Site classification: Suburban 
Limiting Mag. (naked eye):  4.8 
Telescope: 20cm f/6 Eq. Newtonian 
Magnification:  122X 		 Observed Colorations of Components:  All components were white. 
Other comments:   NW of bright sigma.  Well within the same field.  The primary is slightly brighter than the secondary which is also a close pair of nearly 
equal  9th mag. stars (Struve 761b). 

 
Dave Mitsky
Star: Struve 761 
Date & Time: 1/27/99  07:08 UT 
Seeing: 6 <1-10 Seeing Scale (10 best)>
Transparency: ~ 6 
Location of site: ASH Naylor Observatory (http://www.msd.org/obs.htm) 
near Lewisberry, PA 
Site classification: Rural 
Sky darkness: < 5.0 <Limiting magnitude> moonlight 
Telescope: 17" f/15 classical Cassegrain 
Magnification: 118x, 202x, 259x 		 A charming triple star in close proximity to another fine multiple star system, Sigma Orionis.  The three 8th magnitude stars making up this acute triangle appeared to be white. 
 

 
William L. Schart
Star: Struve 761 
Date & Time: 12/26/99 10:29 pm CST
Seeing:  7 <1-10 Seeing Scale (10 best)> 
Location of site: Killeen, TX (Lat 31 N, Elev 600 ft) 
Site classification: Suburban 
Sky darkness: 4.5 <Limiting magnitude> 
Telescope: Orion 6" Dob. 
Magnification: 32x, 48x, 72x, 98x, 144x
 		 Appears in the same field of view as sigma Ori. I though had split it as 32x, but higher power (72x) I found that what I thought was the second member was not, in fact, a member and the other was a tight double that was now split. Going back to 32x, I suspected that I could split it, but could not confirm. Separation is 8", PA 89 degrees. 
 

 
Randall Heckman
Star: Struve 761
Date & Time: 12/30/99 at 3:12 UT 
Seeing: 6 
Location of Site: Heckman Observatory 
40 37' 10" N and 99 03' 50" W 
Site Classification:  Rural 
Sky Darkness (Limiting Magnitude): 4 
Telescope:  8" Orion Dob with 6" aperture mask 
Magnification: 46x 		 Separation (Clear or Toughing): Clear 
Magnitude Comment: Secondary only slightly dimmer. 
Color Comment: White 
General Comment: One of the two components appears to be a double with a          secondary separated by about 12".  According to Burnham's the B component of Struve 761 is a double separated by 8.5" and the pair has magnitudes 8.5 and 9. 
 
 
 
 

 

 
Richard Harshaw
Star: Struve 761 [ADS 4240]
Location of site: Northern Kansas City, Missouri (USA)
94d 30m west longitude, 39d 15m north latitude
980 ft above Mean Sea Level
Date of observations (UT): 0230 on 12/31/99 
Site classification: suburban
Sky conditions: 
seeing-- 8 out of 10 
transparency-- 8 out of 10 
limiting visual magnitude-- 5 
Temperature: 44 F 
Telescope: Celestron C-8 
Eyepiece: Micro-Guide (160x) 		 I made five sets of measurements with the Micro-Guide illuminated reticule eyepiece and got averages of 69" at PA 204 for AB and 9.6" at PA 269 for Bb. (If you want the measurements themselves, reply to this posting.) 

Nearby Sigma Ori is a pest! 
I noted colors of White for all three. 
The system is 142 light years away so is only about 2.1 times as bright as the Sun. 

Measurements from 1931: 
7.9m primary 
8.6m companion, 68" at PA 202 (both appear to be fixed) 
9.0m companion to B, 9" away from it at PA 268 

 

 
Tomás Vazquez
Star: Struve 761 
Date & Time:  15/12/1999, (TU): 23:29:58 
Seeing:  4 <1-10 Seeing Scale (10 best)> 
Location of site: 37 24 N. 5 58 W. Sevilla, Spain 
Site classification: Urban 
Sky darkness: 3  <Limiting magnitude> 
Telescope: Celestron C8” D:203mm. f/6,3 
Magnification: CCD Camera 

 		 Observing Method: CCD ST-4 Camera 
Integration time: 10 seconds 
Software used (reading/treatment): Lucas 1.1 / Laia 3.1g 
Image Position: North up, East left 

The first thing comes to mind when seeing this image is the rich field. Struve is a multiple system and easy to split. The distance between components is 68” with a PA of 202º. If you pay attention to the secondary, you will notice that it’s splitted again into a 9 mag. star located only 9” with a PA of 268. 

In SSE direction you can also see the near located Sigma Orionis, forming a wonderful set of stars. 
 

 

 
Luis Argüelles
Star: Struve 761 
Date & Time:  January, 1, 2000 18:50 UT 
Seeing:  7 <1-10 Seeing Scale (10 best)> 
Location of site: La Olla, Gijón, Spain 
Site classification: Suburban 
Sky darkness: 4-4.5  <Limiting magnitude> 
Temperature: ~ 4C 
Telescope: Televue Ranger 70mm, f/6.8 mounted over a Manfrotto video tripod 
Magnification: 24x, 48x 


 

 This star is really easy to find, just in the same field of view as Sigma Orionis. Struve 761, Sigma Ori and the catalogued star SAO 132412 form the shape of an arrow. Dominik Elsäser and me named this arrow "The Big Orion's arrow" last "33" session. 

SAO 132412 would be the tip of the arrow, while Struve 761 would be the base of the arrow. The two components from Burnham's listing are easy to split even with a magnification as low as 24x (Eudiascopic 20mm eyepiece) and probably you would get the split with a good pair of binoculars. I have not been able to observe the other 3 fainter components of this quintuple system with this aperture from Gijon suburban skies. The sketch represents the field of view at about 60x. 
[see also my log of Sigma Orionis] 
 
 

 

 
Ilario Melandri
Star: Struve 761 
Date & Time:  4/Jan/2000 – 20.31 UTC
Seeing: 9 <1-10 Seeing Scale (10 best)> 
Location of site: Italy, Ravenna, San Romualdo, Lat 44 32’N Lon 12 08’E
Elevation: 0 m
Site classification: Rural 
Sky darkness: 4  <Limiting magnitude>
Temperature: -1C 
Telescope: 150 mm f/15 achromatic refractor 
Magnification: 140 x (eyepiece Plossl Clavé 16 mm)		 Note: the second component seems to be double itself. 

 

 
Bill Becker
Star: Struve 761 
Location of site: Casper, Wyoming Elev. 5200' 
Date of observations: Jan.6,2000 5:35UT 
Site classification: Suburban 
Sky conditions: 
Seeing: 4 
Transp.:4.5 
Telescope: Quantum 4 Maksutov 
Magnification:  85x & 149x 
 

Star: Struve 761 
Location of site: Casper, Wyoming Elev. 5200' 
Date of observations: Feb 16, 2000, 3:38 UT 
Site classification: Suburban 
Sky conditions: 
Seeing: 7 
Magnitude limit (naked eye): 4.0, Moonlight 
Telescope: Quantum 4 Maksutov 
Magnification:  85x to 191x 
 

 Wide pair, no problems despite ever present wind. No colors noted. 
 
 
 
 
 
 
 
 
 
 
 

I also revisited struve 761 and noticed it appears to be a nice triple star. The primary looked blue and at about 200*, the 2 close components, also appearing blue, looked to be about 6" apart.(Just my guess as I have not begun to do any accurate measurements) 

 

 
Richard Bise
Star:Struve 761 
Date & Time: January/7,8/2000 
Seeing: 5 <1-10 Seeing Scale (10 best)> 
Location of site: 20 NW of Tucson Az
32.884N -110.979W
Site classification: Suburban 
Sky darkness: 4  <Limiting magnitude> 
Telescope: 10 inch Meade Dobsonian
Magnification: 49x, 125x (25mm Meade  and 9.7mm Plössls)
 		 Easy at 49X. All white to me. I was confused at first because the third member is not mentioned in the Sky and Tel article list!. 

 

 
Jordi Viver
Star: Struve 761 
Date & Time: 19/01/2000, 22:05 UT 
Seeing: 6 <1-10 Seeing Scale (10 best)> 
Location of Site: Vic (Spain) 41º55’N, 2º19’E 
Elev. 570m 
Site Classification: Suburban 
Sky darkness: 4.7 <Limiting magnitude> 
Temperature: 1ºC 
Telescope: 200mm self-made Newton, Dobsonian 
Magnification: 48x 		 Separation: Very dificult to separe two components. I see tree components. 
Catalog data: Guide 7.0: vM7.7, 7.9, 8.43, D(A-B)1.16’,D(A-C)5.6”,PA(A-B)25.4º,PA(A-C)84º 
General coments: The Moon has 13 days. 
Localization in the same field of Sigma Orionis. 
 
 
 
 
 

 

 
Philippe de Jocas 
Star: Struve 761  
Date & Time: January 22, 1h00-7h300 UT 
Seeing: 3-4 <1-10 Seeing Scale (10 best)>.
Location of site: Ottawa/Hull, Canada
Site classification: Suburban 
Sky darkness: 4.5 <Limiting magnitude>
Temperature: -25C 
Telescope: 6" f5 newtonian
Magnification: 90x, 120x
 		 Sigma Ori and Struve 761 could both be resolved  at 90x, but gained a lot by beeing  seen at 120x, Sigma 761  coming across, with the slight mag. difference, as a nice cat's eye. 
 

 
Jim Brownfield
Star: Struve 761 
Date & Time: 26/01/2000, 6:30 p.m.- 11:30 p.m. EST 
Seeing: 3 – 5 (improving) <1-10 Seeing Scale (10 best)>.
Location of site: Huntsburg, Ohio, USA
Site classification: Suburban 
Sky darkness: 6 mag., could see ST 855, going to 5th mag. star Rho  <Limiting magnitude>
Other observing conditions:  83% humidity, 16 degrees F. with 12" snow on ground going to 84% humidity, 4 degrees F.
Telescope: 13.1"/F4.5 Dobsonian, with 5" aperture mask for the brighter pairs
Magnification: 47x
 
Star: Struve 761   
Date & Time: 1/29/00, 3:30 UT - 10:00 UT 
Seeing: ) 3 improving to 4 <1-10 Seeing Scale (10 best)>.
Location of site: Huntsburg, Ohio, USA
Site classification: Suburban 
Sky darkness: 4.5 (limiting magnitude)
Other observing conditions: 14 degrees F dropping to 6 degrees F, 92% humidity
Telescope: Meade 80mm/ f11
Magnification: 28x, 45x		 split at 47x 
 
 
 
 
 
 
 
 
 
 
 

could just make pair out at 28x, at 45x they were clearly split 
 

 
Daniel Rodríguez
Star: Struve 761 
Date & Time: 1/30/2000, 22:45 (UT)  
Seeing: 5 <1-10 Seeing Scale (10 best)> 
Location of site: Jerez de la Frontera, SPAIN, elev. 24 m 
Site classification: Urban 
Sky darkness: 4  <Limiting magnitude> 
Temperature: 9C 
Telescope: Celestron G8 (8” SCT f/10)
Magnification: 119x (Celestron Plössl 17mm)

 		 Three stars are easily split at 119x. All of them are of similar brightness and results a rather poor system compared to the nearby Sigma Orionis. On the image, Sigma 761 is located left. 
 

 

 
John M. Ryan
Star: Struve 761 
Date of Observation: 2/02/00, 21:15UT
Location of Observation: Ciudad Rodrigo, Salamanca, Spain 
40º 36' N, 6º 32'W, Elev. 800 Meters 
Seeing: 6 to 7, fog began to degrade seeing (1 - 10, 10 best)  
Site classification: Urban
Limiting Mag. (naked eye): 5
Instrument: Meade 8"SCT 
Magnification: 100x		 Separation (Clear or Touching): Clear 
Magnitude Comment:Both components seemed of equal magnitud in accordance with the data. 
Color Comment: Both components appeared white 
General Comment: When I split Sigma last week I noted the double just to the west but I was not aware then it was part of the list of 33. At more than a minute of separation it is an easy split. However reading Richard Harshaw's report I learned that the B component is also a double which I was not aware of. The data list shows Struve 761 as a double. The B component should be easily separated at higher magnification. I will have to return to Sturve 761 to split the B component. 

 
Jay Zimmerman
Star: Struve 761 
Date & Time: 02/08/2000, 0410 UT 
Seeing: 8 <1-10 Seeing Scale (10 best)> 
Location of Site:  Carbondale, IL, USA 
Site Classification: Suburban/near rural 
Temperature: 30°F (-1.11°C) 
Sky darkness: 5.3  <Limiting magnitude> 
Telescope: 97mm, f7 apo 
Magnification: 26.7x , 107x 

 

 Clean split of all three components at 26.7x although the BC pair showed only hairline separation at that power. BC split was much better at about 107x.  Colors: All three appear to be white, but color determination was hindered due to glare from Sigma AB and the fact that my eyepiece kept fogging. 
 
 
 

 

 
Tim Leese
Star: Struve 761 
Date & Time: 19-Feb-2000, 1900-2330 UT.
Seeing: 5/6  <1-10 Seeing Scale (10 best)> 
Location of site: Cheshire. UK
Site classification: Suburban 
Sky darkness: 3 <Limiting magnitude> 
Conditions: High haze, very cold and frosty, sky clearing later but full moon. 
Telescope: 200mm f/6  Newtonian scope  mounted over a Vixen GP mount (manual slow motion).
Magnification: x48, x120		 Observed in the same field of view as Sigma as a narrow triangle of stars NW of Sigma. 
 
 
 
 

 

 
Bill Reinehr
Star: Struve 761 
Date & Time: February 27, 2000, 03:30  UTC
Seeing: 7 (fairly still) <1-10 Seeing Scale (10 best)>
Location of site: Pflugerville, Texas, USA  (30 degrees N.)
Site classification: Suburban 
Sky darkness: 4.1 <Limiting magnitude> 
Temperature: 53 F. 
Telescope: Vixen 80mm Fluorite, f/8  on Custom D altaz mount 
Magnification: 29x, 91x 		 Barely but cleanly split at 29x.  Easily observed in the same FOV as Sigma. 
 
 

 

 
G.E.O.D.A Group
Star: Struve 761 
Date & Time: 10-III-2000, 19:00-21:00 UT
Seeing: 7.5 <1-10 Seeing Scale (10 best)> 
Location of Site: Manises, Valencia, Spain. GPS coordinates: 39º 29' 36" N, 00º 27' 56" W.
Site Classification: Urban-Suburban
Sky darkness: 3 <Limiting magnitude> 
Telescope: Meade 10" LX-200 SCT
Magnification: 200x		 Published measures are the mean of two observations made from two different observers.

d = 79.9; PA = 205