49 Leonis, also cataloged as TX Leonis or Struve 1450, is a variable and binary star in the constellation Leo. It’s best viewed in the springtime in the northern hemisphere.
In 1933, Ernst-Joachim Meyer observed that the brightness of 49 Leonis fluctuated as another star eclipsed it, indicating it is an eclipsing binary. This phenomenon causes 49 Leonis’ magnitude to decrease over a period of two and a half days.1
Adding to the interesting nature of 49 Leonis is the star’s close companion, which lies only 2.2 arcseconds away. You’ll need a calm atmosphere with good transparency to see the binary with your telescope. In my case, I couldn’t see the two stars through my 8-inch SCT scope without my 12mm eyepiece combined with a 2x Barlow. Together, these two pieces raised my power to 339x. At that point, the two points of light were not that clear. The stars constantly quivered due to the unsettled atmosphere above. I knew clouds were forming in the region after sunset, so I expected the scene to look turbulent.
The primary star, at a varying magnitude of around +5.7, appears white. The dimmer secondary companion around magnitude 8.1 appears grey or perhaps light blue.
My Observations
| Date | April 19, 2023 |
| Time | 9:33 p.m. |
| Location | Seattle, WA |
| Magnification | 339x |
| Scope | Meade 8″ SCT |
| Eyepiece | 12mm + 2x Barlow |
| Seeing | Average |
| Transparency | Below Average |
I’ve only had a few minutes at the scope, and I’m already seeing a few patches of clouds between the trees looking west. The forecast calls for the weather to change in the next few hours. I’m glad the scope is aligned well and arrived right at 49 Leonis without adjustment.
Looking through the 12mm eyepiece, I only see a bright white star. I don’t see evidence of any binary here. I run over and grab my lens box and pull out the 2x Barlow and connect it to the eyepiece. As I focus slowly on the target, I see a quivering point of light due to the unstable atmosphere. I stare a little longer and notice the companion beside the bright star. The primary looks white, while the secondary is a dimmer gray or pale blue.
Key Stats
| Constellation | Leo |
| Best Viewing | Spring |
| Visual Magnitude | +5.7 | +7.9 |
| Absolute Visual Magnitude | +.08 |
| Distance from Earth | 430 ly |
| Separation | 2.2″ | 289 AU |
| Position Angle | 156° |
| Orbital Period | 2.4 days |
| Milky Way Location | Orion Spur |
| My Viewing Grade | B |
| Designations | TX Leo, Struve STF 1450, SAO 118380, HD 91636, HR 4148, HIP 51802 |
Sources and Notes
Banner adapted from an illustration created by Pablo Budassi. The illustration is licensed under the Creative Commons Attribution-Share Alike 4.0 International license. Full details here.
1 Wikimedia Foundation. (2023, January 12). TX Leonis. Wikipedia. Retrieved April 22, 2023, from https://en.wikipedia.org/wiki/TX_Leonis
Sketch by Wayne McGraw
The Garden Astronomer 
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