Regulus, or Alpha Leonis, is the brightest star in the constellation Leo. At magnitude 1.35 it is the 21st brightest star in the sky. Regulus is a quadruple star system. Regulus A, the bright star visible to the unaided eye, is a spectroscopic double. A faint companion, Regulus B (HD 87884), is 176 arcsec distant and is also a double star resolvable in large telescopes.
![]() |
The constellation Leo. E-M1iii + 20mm f/1.7 + sparkle-6 filter. ISO 1600, 20 s. |
Constellation photography in urban Santa Fe is difficult because of the large light gradients. The lower right corner of the above image reveals the brighter sky to the south. On this particular night (30 Mar) the measured sky brightness to the north was sqml=19.53, somewhat brighter than average for a moonless night.
![]() |
The constellation Leo. credit: SkySafariAstronomy.com |
Earlier in the evening I was experimenting with a 114mm GSO Cassegrain telescope and used it to image a few double stars.
![]() |
Regulus A (center) and Regulus B. GSO Cassegrain + Sony A7, ISO 400, 5 s. |
Regulus is one of the stars I recently photographed with a diffraction grating.
I was reviewing these earlier data and suddenly realized that all seven Balmer-series hydrogen-absorption lines are visible in the spectrum of Regulus A, a detail that was previously missed.
A closer look at the short-wavelength end:
Some more pictures from the same day, all with the GSO Cassegrain:
![]() |
Mizar and Alcor. Sony A7, ISO 400, 1 sec. |
![]() |
Polaris A + B. Sony A7, ISO 400, 1 sec. |
![]() |
The nearest star. Sony A7, ISO 400, 1/800 sec. (Baader Astrosolar filter). |
![]() |
GSO Cassegrain solar photography |