StarWatch: Moravian College Astronomy
StarWatch for the greater Lehigh Valley
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APRIL  1998

APRIL STAR MAP | INDEX
 
084    APRIL 5, 1998:   Saving Daylight
Do you know why you’re losing that extra hour of sleep this week? If you have been watching the sunrises and sunsets of late, you must have noticed that the lighted hours have lengthened by over three hours since the winter solstice on December 21. Last week’s sunrises were occurring before 6 a.m., and the trend would have continued for the next three months, eventually causing the sun to rise about 4:30 a.m. Most of us would not be ready to greet the dawn at 3 a.m. So we "spring" ahead by one hour, causing the sun to rise at 5:30 a.m. at midsummer and set an hour later in the evening at 8:30 p.m. The result is a day which is more balanced with respect to our waking hours. In essence, this adjustment saves us more useful daylight, hence, Daylight Saving Time. If you live in American Samoa, Hawaii, Puerto Rico, and the Virgin Islands, nothing changes the routine except for an occasional hurricane or typhoon. Stranger, however, is Arizona and most of Indiana which do not heed the credo of readjusting their daylight hours during the spring and summer months, choosing to remain on standard time all the year round.
 
085    APRIL 12, 1998:   Calculating Easter
Have you ever wondered why Easter is observed on different dates each year? The observance of Easter was decreed by the Council of Nicaea (now Iznik, Turkey) in 325 AD to fall on the first Sunday after the fourteenth day of the moon (considered the day of full moon) that occurs on or after March 21, which at the time of the Council, was the Vernal Equinox. The Vernal Equinox represents the first moment of spring, when the sun crosses the celestial equator as it proceeds northward in the sky. The Sunday after the full moon was chosen intentionally because the Church did not want Easter to coincide with the Jewish Feast of the Passover. This year, the full moon occurs on Saturday, April 11. The first Sunday after that date is obviously the 12th. Easter can occur as early as March 22 if the full moon occurs on March 21 and the 21 is a Saturday. Easter’s latest date is April 25 if the full moon occurs on March 20 and the next full moon occurs on Sunday, April 18. The first Sunday after the April 18 would be April 25. Now you know how it’s done. Happy Easter!
 
086    APRIL 19, 1998:   Two Planets and a Moon
When the sun, moon, and planets appear in close proximity to each other or another star, the event is termed a conjunction. As an example, a very precise conjunction of the sun and the moon would be called a solar eclipse. This Thursday morning, the waning crescent moon joins with the already close pairing of Jupiter and Venus to form a spectacular "triple" conjunction low in the east, southeast about 45 minutes before sunrise. The week commences (Monday) with the waning crescent moon hanging low in the southeastern sky about 45 minutes before sunrise. Subsequent mornings will show the moon plodding steadily eastward towards the sunrise position with the crescent rapidly narrowing. If your east, southeastern horizon is unobscured, you will also have noticed two other luminous objects, Venus (brighter) and Jupiter. The week begins with Venus to the right of Jupiter. As the days continue, Venus will gradually overtake Jove, and the moon will do the same. By Thursday morning Venus will be positioned less than ½ degree from Jupiter, and about two lunar diameters from the moon. It will be a grand sight in low powered telescopes or with binoculars if your southeastern horizon is unhindered by trees or buildings. By Friday the moon is too close to the sun to be easily seen, and Venus now easily leads Jupiter.
 
087    APRIL 26, 1998:   Iridium Flares
Iridium flares... It sounds like some terminology left over from the Cold War era, but there are now over 60 Iridium communications satellites orbiting the Earth and their shiny metallic panels can reflect a powerful momentary burst of sunlight that is easily visible if you are in the correct location. The flares are seen as sharp pulses of light. In order to witness a burst, you must coordinate your watch to within a few seconds of accuracy, but this can be done by watching the Weather Channel. The astronomy section of the ASD Planetarium Home Page can link you to the atomic clock at the US Naval Observatory in Washington, DC. The Iridium flares listed below are fairly accurate for a 10 mile radius around Allentown. However, if you’re on the Internet, go to the ASD Planetarium's astronomy links page and then Space Exploration/Satellites, GSOC Satellite Predictions for more accurate positioning.

Sunday, April 26 insert:
On Sunday, the brightest flare, nearly as luminous as Sirius, the brightest star of the nighttime sky, occurs at 8:15:46 p.m. Look high in the SE about 15 degrees below the zenith. Look for more updates as the week continues. Complete Iridium sightings at...

Monday, April 27 insert:
On Monday a really bright flare occurs at 8:09:44 p.m. when a burst of light about five times brighter than the planet Venus glints in the SE, about 15 degrees below the zenith. Look for more updates as the week continues. Complete Iridium sightings at the home page below.

Tuesday, April 28 insert:
On Tuesday, two -1 magnitude flares occur at 8:03:20 p.m. (Iridium 59) and 9:48:28 p.m. (Iridium 35). The first one is visible in the SE about 20 degrees from the zenith, while the second event can be seen in the E, about halfway up in the sky. Look for more updates as the week continues. Complete Iridium sightings at the home page below.

Wednesday, April 29 insert:
On Wednesday, look for an incredibly bright glint to occur at 9:42:25 p.m. (Iridium 34). The -7 event, over 10 times brighter than Venus, happens in the E, midway up in the sky. Look for more updates as the week continues. Complete Iridium sightings at the home page below.

Thursday, April 30 insert:
On Thursday, a blast of light brighter than Venus occurs 10:58:00 p.m. (Iridium 52). Look NE just over one fist width (13 degrees) above the horizon. On Friday morning you can catch another flare brighter than Venus from Iridium 47 at 5:51:19 a.m. in the N-NE about one third of the way above the horizon. Look for more updates as the week continues. Complete Iridium sightings at the home page below.

Friday, May 1 insert:
On Friday a modest 0 magnitude glint is visible low in the NE about 10:45:31 p.m. (Iridium 62). On Saturday a -5 blast (brighter than Venus) can be seen at 10:49:07 p.m. in the NE only 16 degrees (one fifth of the way) above the horizon. Look for a continuation of Iridium flashes next week. Complete Iridium sightings at the home page below.

Important Information:
The intensity of these flares is very sensitive to your position, so please
try to specify your coordinates as accurately as possible. A position error of
10km on the ground can change the flare intensity by several visual magnitudes! Complete Iridium sightings at the home page below.

Full Iridium Flare Infomation
Observer's Location: Allentown (40.60°N, 75.47°W)
Local Time: Eastern Daylight Time (GMT - 4:00)

DateTimeIntensity
(Mag.)
Elev.AzimuthMirror
Angle
Satellite
26 Apr 23:06:03 3 10° 40° (NE) 3.8° Iridium 53
27 Apr 03:12:05 -4 10° 116° (SE) 0.2° Iridium 66
27 Apr 03:14:19 -4 11° 116° (SE) 0.4° Iridium 67
27 Apr 03:30:59 1 18° 117° (SE) 1.9° Iridium 68
27 Apr 20:09:44 -6 72° 122° (SE) 0.4° Iridium 33
27 Apr 21:54:30 0 47° 76° (E ) 3.2° Iridium 7
27 Apr 23:00:02 2 10° 40° (NE) 2.6° Iridium 54
28 Apr 20:03:18 -1 71° 120° (SE) 2.2° Iridium 59
28 Apr 20:06:06 -2 75° 129° (SE) 1.7° Iridium 60
28 Apr 21:48:28 -1 47° 77° (E ) 1.7° Iridium 35
28 Apr 21:51:05 -3 46° 79° (E ) 0.8° Iridium 61
28 Apr 23:03:27 2 12° 41° (NE) 2.8° Iridium 12
29 Apr 03:05:39 -1 11° 120° (SE) 0.9° Iridium 62
29 Apr 03:17:35 -5 16° 121° (SE) 0.1° Iridium 63
29 Apr 03:29:10 1 22° 122° (SE) 2.5° Iridium 64
29 Apr 21:42:24 -7 46° 78° (E ) 0.0° Iridium 34
29 Apr 22:47:59 0 10° 41° (NE) 1.3° Iridium 14
29 Apr 22:57:29 1 12° 42° (NE) 1.6° Iridium 16
30 Apr 02:54:48 2 117° (SE) 3.3° Iridium 64
30 Apr 03:01:52 0 10° 122° (SE) 1.5° Iridium 67
30 Apr 03:04:31 -0 12° 122° (SE) 1.1° Iridium 65
30 Apr 03:10:44 -2 15° 122° (SE) 0.6° Iridium 66
30 Apr 05:57:17 -3 29° 30° (NE) 0.5° Iridium 25
30 Apr 22:41:57 1 10° 42° (NE) 2.0° Iridium 56
30 Apr 22:51:27 -1 13° 43° (NE) 0.2° Iridium 50
30 Apr 22:58:00 -5 13° 47° (NE) 0.2° Iridium 52
30 Apr 23:01:07 1 16° 46° (NE) 2.7° Iridium 54
01 May 02:55:51 0 10° 124° (SE) 1.5° Iridium 68
01 May 05:51:19 -5 28° 29° (NE) 0.2° Iridium 47
01 May 21:30:20 0 45° 80° (E ) 3.5° Iridium 8
01 May 22:35:57 2 10° 42° (NE) 3.1° Iridium 10
01 May 22:45:31 -0 13° 44° (NE) 1.0° Iridium 9
02 May 03:02:39 0 15° 126° (SE) 1.4° Iridium 62
02 May 03:16:34 -1 22° 127° (SE) 1.2° Iridium 63
02 May 05:36:41 3 21° 30° (NE) 3.7° Iridium 49
02 May 05:45:25 -3 27° 29° (NE) 0.4° Iridium 26
02 May 21:33:27 0 55° 80° (E ) 3.7° Iridium 19
02 May 22:39:33 1 13° 46° (NE) 2.3° Iridium 13
02 May 22:49:07 -5 16° 48° (NE) 0.1° Iridium 14
02 May 22:58:38 1 21° 50° (NE) 3.1° Iridium 16
03 May 02:55:01 2 14° 125° (SE) 3.0° Iridium 64
03 May 03:05:06 -2 18° 128° (SE) 0.8° Iridium 65
03 May 03:09:36 -5 21° 128° (SE) 0.1° Iridium 66
03 May 05:30:53 2 20° 29° (NE) 2.8° Iridium 22
03 May 05:39:27 1 26° 27° (NE) 1.8° Iridium 23
03 May 05:40:48 1 27° 27° (NE) 1.9° Iridium 48
03 May 21:27:23 -1 55° 81° (E ) 1.8° Iridium 36

 

April Star Map

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