Tau Leonis 

William L. Schart
Star: Tau Leonis  
Date & Time: 4/16/99 11:40 pm CDT 
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 <Limiting magnitude>  
Telescope: Orion 6" Dob.  
Magnification: 32x, 98x 
 
Star: Tau Leonis  
Date & Time: April 9, 2000 9:27 pm CDT 
Seeing: 8 <1-10 Seeing Scale (10 best)>  
Location of site: Killeen, TX (Lat 31 N, Elev 600 ft)  
Site classification: Suburban  
Sky darkness: 3.5 <Limiting magnitude>  
Telescope: Orion 6" Dob.  
Magnification: 32x, 48x, 98x 
 
Widely spaced double easily split. Separation 1’ 28.5”, PA 180°. Primary seemed to be yellow, while the secondary was blue. 
 
 
 
 
 
 
 
 
 
Wide spread double easily split at any power. Located by star-hopping from theta via sigma. The primary was a nice golden color and the secondary appeared blue in contrast, although not as blue as Albiero. To the east was a triangular asterism and to the west was another pair, which I ID'ed as STF 1540. Separation for tau was 89", PA 177d. Separation on 1540 was 30:", PA 147d. 
 
 
 
 
 
 
 

 
 
 

 

 
 
Richard Harshaw
Star: Tau Leo [84 Leo; SI 19; SAO 118875; HD 99648] 
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): 0300, 02-28-00  
LT:  2100, 02-27-00 
Site classification: suburban 
Sky conditions 
seeing-- 6 out of 10 up to 8 (varied quickly and often)  
transparency--  5 out of 10 up to 8 (high, thin clouds were in the area) 
limiting visual magnitude: 4.5  
Temperature: 40F  
Telescope: Celestron C-8  
Eyepiece: Micro-Guide (160x)  
 
 
Primary, 5.0 mag, G8III 
Companion B, 7.4 mag; 91" sep at PA 176 (sep decreasing, PA increasing) 
Companion D, 10.0 mag; 65" sep at PA 92 (not seen) 

I made five pairs of separation and PA measures using the Micro-Guide and got an average of 90.6" in PA 180.  The PA is definitely increasing and the separation may be decreasing a wee bit. 

I noted colors of yellow and bluish-white.  D was not noted. 

This star is a member of the Sirius Group and an infra-red source. 

First measured in 1834 (95" @ 170).  AD first measured in 1875 (65" @ 92) and had not changed by 1910. 
 

 
 
Tom Teague
Star: Tau Leo  
Date & Time: 2000 February 28 (2200 UT) 
Seeing: 5 <1-10 Seeing Scale (10 best)>. 
Location of site: Chester, England (53 11 08N; 02 51 39W) 
Site classification: Suburban  
Sky darkness: 4 (in the very few clear patches of sky) <Limiting magnitude> 
Telescope: 63mm Zeiss Telementor refractor 
Magnification: x34, x252 
 
 
This pair is wide and easy, even through cloud.  Primary seems white to me.  No colour seen in companion, but it was faint through cloud obscuration.  I measured the pair with a ring micrometer (3 transits) with the following (unreliable!) result: 
 
                    PA = 180 degrees; 
                    Sep = 88.9" 
 
This is in very good agreement with Richard Harshaw's measurement of yesterday night (27 Feb).  However, his separation measure is clearly more accurate than mine (see below).  I am confident I could improve my accuracy by the simple expedient of choosing a clear night!  At this separation, the ring method is capable of attaining an accuracy comparable with a filar micrometer (as is the Micro Guide). 

The most recent published measurement of this pair was made in 1994, with the following result: 
 
                    PA = 180 degrees; 
                    Sep = 89.7" 
 
It is instructive to compare this with the figures obtained by Richard Harshaw and myself.  We have both arrived at exactly the same PA.  Richard's separation figure is remarkably close to the 1994 measure.  Mine is in pretty good agreement, despite the abysmal observing conditions. 

Note: The measure of this pair that I posted yesterday was not corrected for differential refraction.  The corrected figures are:- 

                    PA = 180 degrees; 
                    Sep = 89.0". 
 

 
 
Mike Nebelsick
Star: Tau Leo 
Date & Time: 
2000 March 06 (0250 UT) 
2000 March 05 (2050 CST) 
Location of Site: Naperville, IL USA (41d 47m North; 88d 15m West) 
Site classification: Suburban 
Temperature: 45 F 
Seeing: 7 <1-10 Seeing Scale (10 best)> 
Sky darkness: 4 <Limiting magnitude> 
Transparency: 5/10 
Telescope: Meade ETX90 (90mm Mak-Cas) 
Magnification: 48x (26mm Super Plossl) 
 
Very easily wide pair at 48X. 

Very pretty pair, Primary golden yellow. Companion very blue. 

PA Estimated to be 190. (not measured) 

Also in the same (65') FOV is another pretty double, (NW of Tau) 83 Leo. The separation is something like 1/3 that of Tau, (eyeball guess) and the PA about 165 (again estimated). Golden Primary, with a golden/orange companion. Makes for a nice, interesting field at low power. 
 

 
 

 

 
 
Dave Mitsky
Star: Tau Leo 
Date & Time: 2000/3/6 02:30 UT   
Seeing: 6 <1-10 Seeing Scale (10 best)>. 
Transparency: ~ 8   
Location of site: ASH Naylor Observatory (http://www.msd.org/obs.htm)  
near Lewisberry, PA  
Site classification: Rural  
Sky darkness: ~ 5.0 <Limiting magnitude>  
Telescope: 17" f/15 classical Cassegrain  
Magnification: 118x, 259x 
Oculars (17"): 55mm University Optics Ploessl (118x), 
25mm U.O. MK-70 (259x) 

 

Tau Leonis is a very wide (91.1") and fairly bright binary star that was easily resolved at 118x.  The pale blue 7.0 magnitude secondary is almost due south of the 5.5 magnitude primary. 

 

 
 
Tim Leese
Star: Tau Leo 
Date & Time: 28/29 March 2000  (22.15UT-0100UT)  
Seeing: 6-7 <1-10 Seeing Scale (10 best)>  
Location of site: Cheshire. UK, 53° 15? N –2? 33?W 
Site classification: Suburban  
Sky darkness: 3.6 - 4.3 <Limiting magnitude>  
Telescope: 200mm f/6  Newtonian scope  mounted over a Vixen GP mount (manual slow motion). 
Magnification: x60, x192 
Reported PA or SEP estimated using 12.5 mm Celestron microguide
At a magnification of x60 a creamy/white star with a pale blue companion was seen. At x 192 I attempted to measure the PA and found it to be 179? (avg of 2) with a SEP of 93.5? (avg of 2) 
 
 
 
Ilario Melandri
Star: Tau Leo  
Date & Time: 30 Mar 2000 – 23.57 UTC   
Seeing: 5 <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: 6 <Limiting magnitude> 
Temperature: +6C 
Telescope: 150 mm f/15 achromatic refractor (lens by Romano Zen, Venice) 
Magnification: 140 x (eyepiece Plossl Clavé 16 mm) 
 
 
  
 
 
Philippe de Jocas 
Star: Tau Leo 
Date & Time: March, 24-25   
Seeing: fair to good, 4 to 6 <1-10 Seeing Scale (10 best)>. 
Location of site: Ottawa/Hull, Canada 
Site classification: Suburban  
Sky darkness: 4.4-4.5 <Limiting magnitude> 
Temperature: 6-7C, , light Westerly winds and slighltly hazy skies 
Telescope: 6" f5 newtonian 
Magnification: 40x  
 
Tau Leo and 83 Leo. Like many I find that star field quite pretty. In fact i even got it sketched a year ago almost to the day (Mar 27, 99). Very pleasant sight at 40x.To my eyes 83 Leo looked like two silver spots side by side(which is strange considering the G and K spectra). 
 
 
 
Bill Reinehr
Star: Tau Leo  
Date & Time: April 09, 2000, 03:30  UTC   
Seeing: 7 <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: 48 F. 
Telescope: Vixen 80mm Fluorite, f/8  on Custom D altaz mount   
Magnification: 29x 
 
Split at 29x. Rather bright yellow primary. No color noted for secondary. 

Separation: Clear 
 
 

 
 
 

 
 

 
 
Eddy O'Connor
Star: Tau Leo 
Date & Time: 11/04/2000, 9 p.m. local time 
Seeing: 5 <1-10 Seeing Scale (10 best)> 
Location of Site: Lat.34.52S.; Long.150.38E 
Site Classification: Suburban 
Sky darkness: 5 (6 day-old Moon) <Limiting magnitude> 
Telescope: Vixen 102mm, 1000mm FL. 
Magnification: 50x (K20mm), 80x (Ortho. 12.5mm) 
 
 
This was an easy object to locate, the brightest star in an open crown of four stars. At lowest power X80 the primary was bright yellow and the secondary, well separated and about three magnitudes dimmer, was bluish. Triangle of stars in field. 

Ambience: Southern sky darker tonight but seeing is rapidly deteriorating. Flock of geese (or perhaps Teal) passed overhead with plaintive calls. Tripped over the garden hose and called it a night. The following morning (Truth!) letter from my bank offered Accident Death Plan Policy. Eddy 
 

 
 
Rafaello Braga 
Star: Tau Leo 
Date & Time: 22.04.2000, 22.50 UT 
Seeing: 3 (bad) <1-10 Seeing Scale (10 best)> 
Location of Site: Corsico, Italy 
Site Classification: suburban 
Sky darkness: about 3.5, windy <limiting magnitude> 
Telescope: 75mm (3") f/6.7 Pentax apo refractor 
Magnification: 20x (Plossl 25 mm) 
 
Easy (89.6 arcsec), very beautiful. A orange-yellow, B pale blue. In the same field with 83 Leo, cleanly splitted at 20x only (A 6.5, B 7.6, 150°, 28.4 arcsec), better seen at 40x (Plossl 25 + Barlow 2x): A orange, B whitish (old Authors said ruddy or lilac, but is difficult to estimate). 

 
 
 

 
 
Patrick J. Anway 
Star: Tau Leo 
Date & Time: April, 23, 2000  02:00 UT 
Seeing: 8 <1-10 Seeing Scale (10 best)> 
Location of Site: Munising Michigan USA 
Site Classification: Rural 
Sky darkness: 6 <limiting magnitude> 
Sky condition: No moon - just below horizon; no clouds 
Temperature: 28*F   -2*C 
Telescope: Zeiss Telementor 63mm, f/13.3 on equatorial mount 
Magnification: 34x (Vixen 25mm orthoscopics) 
 
An easy slit for the 2.5" even at 34X. The primary is a bright yellow and the companion shows a trace of blue in it's white color. There was another double close by and later checked "Guide" to identify as 83 Leo, a pair of 6.5 and 7.5 mag. and 29" separation.