Editing Regulus (section)

== Observation ==

[[File:Regulus 1.JPG|thumb|Regulus through Celestron CGEM DX 1100 @ F6.3, Canon T3i, Televue 4X Powermate, ISO 800, 30 sec exposure|alt=|left]]
The Regulus system as a whole is the twenty-first [[Brightest stars|brightest star]] in the night sky with an [[apparent magnitude]] of +1.35. The light output is dominated by Regulus A. Regulus B, if seen in isolation, would be a binocular object of magnitude +8.1, and its companion, Regulus C, the faintest of the three stars that has been directly observed, would require a substantial telescope to be seen, at magnitude +13.5. Regulus A is itself a spectroscopic binary; the secondary star has not yet been directly observed as it is much fainter than the primary. The BC pair lies at an angular distance of 177 arc-seconds from Regulus A, making them visible in amateur telescopes.<ref name="pugh"/>
[[File:MVI 3269-Regulus-1.png|thumb|Regulus as viewed through a 110mm refractor in full daylight.|alt=|left]]

Regulus is 0.465 degrees from the [[ecliptic]],<ref name=pratt/> the closest of the bright stars, and is often [[occultation|occulted]] by the [[Moon]]. This occurs in spates every 9.3 years, due to [[lunar precession]]. The last spate was around 2017, with occultations every month from December 2016 till July 2017, each one limited to certain areas on Earth.<ref>See [https://web.archive.org/web/20160309173111/http://www.lunar-occultations.com/iota/bstar/bstar.htm 2016 Bright Star Occultations] and [https://web.archive.org/web/20170307064802/http://www.lunar-occultations.com/iota/bstar/bstar.htm 2017 Bright Star Occultations].</ref> Occultations by [[Mercury (planet)|Mercury]] and [[Venus]] are possible but rare, as are occultations by [[asteroid]]s.  Seven other stars which have a [[Bayer designation]] are less than 0.9° from the ecliptic (perfected, mean plane of Earth's orbit and mean apparent path of the Sun) the next brightest of which is [[Delta Geminorum|δ (Delta) Geminorum]], of magnitude +3.53.  

The last occultation of Regulus by a planet was on July 7, 1959, by Venus.<ref name="planets" /> The next will occur on October 1, 2044, also by Venus. Other planets will not occult Regulus over the next few millennia because of their [[orbital node|node positions]]. An occultation of Regulus by the asteroid [[166 Rhodope]] was filmed in Italy on October 19, 2005. Differential bending of light was measured to be consistent with [[general relativity]].<ref name="rhodope"/> Regulus was occulted by the asteroid [[163 Erigone]] in the early morning of March 20, 2014.<ref name=sigismondi/> The center of the shadow path passed through [[New York (state)|New York]] and [[eastern Ontario]], but no one is known to have seen it, due to cloud cover. The International Occultation Timing Association recorded no observations at all.<ref name=iota/>

Although best seen in the evening in the northern hemisphere's late winter and spring, Regulus appears at some time of night throughout the year except for about a month (depending on ability to compensate for the sun's glare, ideally done so in twilight) on either side of August 22–24, when the Sun is too close.<ref name=skymap/> The star can be viewed the whole night, crossing the sky, in late February. Regulus passes through [[Solar and Heliospheric Observatory|SOHO]]'s [[Large Angle and Spectrometric Coronagraph|LASCO]] C3 every August.<ref name="SOHO" /> 

For Earth observers, the [[heliacal rising]] (pre-sunrise appearance) of Regulus occurs late in the first week of September, or in the second week. Every 8 years, [[Venus]] passes very near the star system around or a few days before the heliacal rising, as on 5 September 2022 (the superior conjunction of Venus happens about two days earlier with each turn of its 8-year cycle, so as this cycle continues Venus will more definitely pass Regulus ''before'' the star's heliacal rising).{{cn|date=September 2022}}