A total solar eclipse occurred at the Moon's ascending node of orbit on Monday, April 28, 1930,[1] with a magnitude of 1.0003. It was a hybrid event, with only a fraction of its path as total, and longer sections at the start and end as an annular eclipse. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. The Moon's apparent diameter was near the average diameter because it occurred 7.2 days after apogee (on April 21, 1930, at 13:50 UTC) and 6 days before perigee (on May 4, 1930, at 19:50 UTC).[2]
Annularity was first visible in the eastern Pacific Ocean, then totality from California, Nevada, Oregon, Idaho and Montana, with annularity continuing northeast across the remainder of Montana and into central and eastern Canada and northern Labrador of the Dominion of Newfoundland (today's Newfoundland and Labrador in Canada). A partial eclipse was visible for parts of Hawaii, North America, and the northern Soviet Union.
During a hybrid solar eclipse, the apex of the moon's umbral cone was very close to the Earth's surface, and the magnitude was very large. The edges of the moon and the sun were very close to each other as seen from the Earth in both the total and annular portion of the path. A series of Baily's beads on the lunar limb provided an excellent opportunity to measure the size and shape of the Earth, as well as the mountains and valleys on the lunar limb. Scientists recorded the precise time of each phase of the eclipse in Camptonville, California. Because the duration of totality was just more than 1 second, the photographic film needed to be inserted quickly after the start of totality. In addition, scientists recorded audio images with a long-wave receiver on an aircraft at the Mare Island Naval Shipyard. Each image had a time accurate to 1/5 second.
Prior to it, the hybrid solar eclipse of April 17, 1912, also belonging to Solar Saros 137, also occurred with a magnitude close to 1. Observations were made near Paris, France. Similar observations were also made during the annular solar eclipses of May 9, 1948 in Rebun Island, Japan and May 20, 1966 in Greece and Turkey, also belonging to the same solar Saros cycle.[3]
Shown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.[4]
| First Penumbral External Contact | 1930 April 28 at 16:20:27.5 UTC | |
| First Umbral External Contact | 1930 April 28 at 17:25:43.5 UTC | |
| First Central Line | 1930 April 28 at 17:26:14.8 UTC | |
| Greatest Duration | 1930 April 28 at 17:26:14.8 UTC | |
| First Umbral Internal Contact | 1930 April 28 at 17:26:46.1 UTC | |
| Greatest Eclipse | 1930 April 28 at 19:03:34.0 UTC | |
| Ecliptic Conjunction | 1930 April 28 at 19:08:43.9 UTC | |
| Equatorial Conjunction | 1930 April 28 at 19:27:27.4 UTC | |
| Last Umbral Internal Contact | 1930 April 28 at 20:40:09.2 UTC | |
| Last Central Line | 1930 April 28 at 20:40:37.6 UTC | |
| Last Umbral External Contact | 1930 April 28 at 20:41:06.0 UTC | |
| Last Penumbral External Contact | 1930 April 28 at 21:46:24.5 UTC |
| Eclipse Magnitude | 1.00026 | |
| Eclipse Obscuration | 1.00053 | |
| Gamma | 0.47305 | |
| Sun Right Ascension | 02h21m32.7s | |
| Sun Declination | +14°06'03.1" | |
| Sun Semi-Diameter | 15'52.8" | |
| Sun Equatorial Horizontal Parallax | 08.7" | |
| Moon Right Ascension | 02h20m46.1s | |
| Moon Declination | +14°30'42.8" | |
| Moon Semi-Diameter | 15'39.8" | |
| Moon Equatorial Horizontal Parallax | 0°57'29.0" | |
| ΔT | 24.0 s |
See also: Eclipse cycle. This eclipse is part of an eclipse season, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by a fortnight.
| April 28 Ascending node (new moon) | ||
| Partial lunar eclipse Lunar Saros 111 | Hybrid solar eclipse Solar Saros 137 |