* Astronomy

Friedrich Schmiedl launched the first rocket mail in 1931
http://en.wikipedia.org/wiki/Rocket_mail#Pioneers

The Transit 5BN-3 military satellite failed to reach orbit on the 21st April, 1964 and 2.1 pounds of radioactive plutonium was spread over a wide area.
http://astronomy.activeboard.com/t42420591/transit-5bn-3-satellite/

LEGRI was successfully launched on April 21st, 1997, on a Pegasus XL rocket. 
http://en.wikipedia.org/wiki/LEGRI

Apollo 16's lunar module landed successfully in the Descartes Highlands on April 21, 1972
http://astronomy.activeboard.com/t42335037/apollo-16/

NGC 3011 (also MCG 5-23-38, UGC 5259 and PGC 28259) is a magnitude 13.3 spiral galaxy located 71 million light-years away away in the constellation Leo.
The galaxy was discovered by America astronomer Lewis Swift using a 40.64 cm (16 inch) refractor on the 21st April 1886.
Right Ascension 09h 49m 41.1s, Declination Dec +32° 13' 18"
http://astronomy.activeboard.com/t57353213/ngc-3011/

NGC 3742 (also MCG -6-26-1 and PGC 35833) is a magnitude 12.1 spiral galaxy located 125 million light-years away away in the constellation Centaurus.
The galaxy was discovered by British astronomer John Herschel using a 45.72 cm (18 inch) f/13 speculum reflector at the Cape of Good Hope on the 21st April 1835.
Right Ascension 11h 35m 32.1s, Declination Dec -37° 57' 22"
http://astronomy.activeboard.com/t57352675/ngc-3742/

NGC 3749 (also IRAS 11333-3743, MCG -6-26-2 and PGC 35861) is a magnitude 12.3 spiral galaxy located 124 million light-years away away in the constellation Centaurus.
The galaxy was discovered by British astronomer John Herschel using a 45.72 cm (18 inch) f/13 speculum reflector at the Cape of Good Hope on the 21st April 1835.
Right Ascension 11h 35m 53.0s, Declination Dec -37° 59' 51"
http://astronomy.activeboard.com/t57352646/ngc-3749/

NGC 3783 (also IRAS 11365-3727, MCG -6-26-4 and PGC 36101) is a magnitude 11.9 barred spiral galaxy located 134 million light-years away away in the constellation Centaurus.
The galaxy was discovered by British astronomer John Herschel using a 45.72 cm (18 inch) f/13 speculum reflector at the Cape of Good Hope on the 21st April 1835.
Right Ascension 11h 39m 01.7s, Declination Dec -37° 44' 18"
http://astronomy.activeboard.com/t42189285/ngc-3783/

NGC 3799 (also Arp 83, MCG 3-30-37, UGC 6630 and PGC 36193) is a magnitude 13.8 spiral galaxy located 152 million light-years away away in the constellation Leo.
The galaxy was discovered by British astronomer John Herschel using a 45.72 cm (18 inch) f/13 speculum reflector at the Cape of Good Hope on the 21st April 1832.
Right Ascension 11h 40m 09.3s, Declination Dec +15° 19' 39"
http://astronomy.activeboard.com/t57353186/ngc-3799/

NGC 3806 (also MCG 3-30-42, UGC 6641 and PGC 36231) is a magnitude +13.6 face-on spiral galaxy located 160 million light-years away away in the constellation Leo.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 11h 40m 46.7s, Declination Dec +17° 47' 44"
http://astronomy.activeboard.com/t57353167/ngc-3806/

NGC 4109 (also MCG 7-25-24 and PGC 38427) is a magnitude 14.1 face-on barred spiral galaxy located 324 million light-years away away in the constellation Virgo.
The galaxy was discovered by astronomer Bindon Blood Stoney, assistant to William Parsons using the 'Parsonstown Leviathan', a 182.88 cm(72 inch) speculum reflector on the 21st April 1851.
Right Ascension 12h 06m 51.1s, Declination Dec +42° 59' 46"
http://astronomy.activeboard.com/t57353137/ngc-4109/

NGC 4257 (also MCG 1-31-49 and PGC 39624) is a magnitude +14.0 spiral galaxy located 127 million light-years away away in the constellation Virgo.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 12h 19m 06.5s, Declination Dec +05° 43' 34"
http://astronomy.activeboard.com/t57353110/ngc-4257/

NGC 4301 (also NGC 4303A, IRAS12198+0450, UGC 7439, MCG 1-32-27 and PGC 40087) is a magnitude 12.9 barred spiral galaxy located 58 million light-years away away in the constellation Virgo.
The galaxy was discovered by astronomer Bindon Blood Stoney, assistant to William Parsons using the 'Parsonstown Leviathan', a 182.88 cm(72 inch) speculum reflector on the 21st April 1851.
Right Ascension 12h 22m 27.2s, Declination Dec +04° 33' 57"
http://astronomy.activeboard.com/t57352570/ngc-4301/

NGC 4584 (also MCG 2-32-162, UGC 7803 and PGC 42223) is a magnitude +12.9 spiral galaxy located 82 million light-years away away in the constellation Virgo.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 12h 38m 17.8s, Declination Dec +13° 06' 38"
http://astronomy.activeboard.com/t57353085/ngc-4584/

NGC 4585 (also IRAS 12357+2912, MCG 5-30-42 and PGC 42215) is a magnitude +14.1 spiral galaxy located 335 million light-years away away in the constellation Coma Berenices.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 12h 38m 13.2s, Declination Dec +28° 56' 14"
http://astronomy.activeboard.com/t57353053/ngc-4585/

NGC 4767 (also MCG -6-28-23 and PGC 43845) is a magnitude 11.5 elliptical galaxy located 138 million light-years away away in the constellation Centaurus.
The galaxy was discovered by British astronomer John Herschel using a 45.72 cm (18 inch) f/13 speculum reflector at the Cape of Good Hope on the 21st April 1835.
Right Ascension 12h 53m 52.9s, Declination Dec -39° 42' 52"
http://astronomy.activeboard.com/t57352559/ngc-4767/

NGC 4822 (also MCG -2-33-69 and PGC 44236) is a magnitude 13.3 lenticular galaxy located 180 million light-years away away in the constellation Virgo.
The galaxy was discovered by German astronomer Wilhelm Tempel using a 27.94 cm (11 inch) refractor at the Arcetri observatory on the 21st April 1882.
Right Ascension 12h 57m 03.6s, Declination Dec -10° 45 44"
http://astronomy.activeboard.com/t57353045/ngc-4822/

NGC 4848 (also IRAS 12556+2830, MCG 5-31-39, UGC 8082 and PGC 44405) is a magnitude +13.7 spiral galaxy located 324 million light-years away away in the constellation Coma Berenices.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 12h 58m 05.7s, Declination Dec +28° 14' 33"
http://astronomy.activeboard.com/t50127463/ngc-4848/

NGC 4851 (also NGC 4851-1 and PGC 44439) is a magnitude 14.2 spiral galaxy located 361 million light-years away away in the constellation Coma Berenices.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 12h 58m 21.8s, Declination Dec +28° 08' 52"
http://astronomy.activeboard.com/t57353003/ngc-4851/

NGC 4858 (also IRAS 12566+2823, MCG 5-31-51 and PGC 44535) is a magnitude 15.2 spiral galaxy located 433 million light-years away away in the constellation Coma Berenices.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 12h 59m 02.3s, Declination Dec +28° 06' 55"
http://astronomy.activeboard.com/t57352971/ngc-4858/

NGC 4859 (also MCG 5-31-53, UGC 8097 and PGC 44534) is a magnitude 13.6 spiral galaxy located 329 million light-years away away in the constellation Coma Berenices.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 12h 59m 01.9s, Declination Dec +26° 48' 56"
http://astronomy.activeboard.com/t57352871/ngc-4859/

NGC 4887 (also IRAS 12580-1423, MCG -2-33-87 and PGC 44796) is a magnitude 13.6 lenticular galaxy located 124 million light-years away away in the constellation Virgo.
The galaxy was discovered by German astronomer Wilhelm Tempel using a 27.94 cm (11 inch) refractor at the Arcetri observatory on the 21st April 1882.
Right Ascension 13h 00m 39.3s, Declination Dec -14° 40' 00"
http://astronomy.activeboard.com/t57352790/ngc-4887/

NGC 4891 is a magnitude 13.2 star located in the constellation Virgo.
The star was discovered by German astronomer Wilhelm Tempel using a 27.94 cm (11 inch) refractor at the Arcetri observatory on the 21st April 1882.
Right Ascension 13h 00m 47.0s, Declination Dec -13° 25' 33"
http://astronomy.activeboard.com/t57352724/ngc-4891/

NGC 4897 (also IRAS 12583-1310, MCG -2-33-89, UGCA 316 and PGC 44829) is a magnitude 11.8 spiral galaxy located 117 million light-years away away in the constellation Virgo.
The galaxy was discovered by German astronomer Wilhelm Tempel using a 27.94 cm (11 inch) refractor at the Arcetri observatory on the 21st April 1882.
Right Ascension 13h 00m 52.9s, Declination Dec -13° 26' 56"
http://astronomy.activeboard.com/t57352474/ngc-4897/

NGC 5102 (also IRAS 13191-3622, MCG -6-29-31, ESO 382-50 and PGC 46674) is a magnitude 10.4 lenticular galaxy located 12.1 ±0.7 million light-years away away in the constellation Centaurus.
The galaxy was discovered by British astronomer John Herschel using a 45.72 cm (18 inch) f/13 speculum reflector at the Cape of Good Hope on the 21st April 1835.
Right Ascension 13h 21m 57.6s, Declination Dec -36° 37' 49"
http://astronomy.activeboard.com/t33442665/ngc-5102/

NGC 5454 (also MCG 3-36-42, UGC 8997 and PGC 50192) is a magnitude 12.7 lenticular galaxy located 353 million light-years away away in the constellation Boötes.
The galaxy was discovered by German-Danish astronomer Heinrich Louis d'Arrest using a 27.94 cm (11 inch) refractor on the 21st April 1865.
Right Ascension 14h 04m 45.7s, Declination Dec +14° 22' 55"
http://astronomy.activeboard.com/t57351870/ngc-5454/

NGC 5788 (also MCG 9-24-49 and PGC 53189) is a magnitude 14.7 spiral galaxy located 508 million light-years away away in the constellation Boötes.
The galaxy was discovered by America astronomer Lewis Swift using a 40.64 cm (16 inch) refractor on the 21st April 1887.
Right Ascension 14h 53m 16.8s, Declination Dec +52° 02' 41"
http://astronomy.activeboard.com/t57351834/ngc-5788/

NGC 5932 (also MCG 8-28-33 and PGC 55109) is a magnitude 14.3 spiral galaxy located 525 million light-years away away in the constellation Boötes.
The galaxy was discovered by America astronomer Lewis Swift using a 40.64 cm (16 inch) refractor on the 21st April 1887.
Right Ascension 15h 26m 48.2s, Declination Dec +48° 36' 54"
http://astronomy.activeboard.com/t57351808/ngc-5932/

NGC 5933 (also MCG 8-28-34 and PGC 55117) is a magnitude 14.9 lenticular galaxy located 499 million light-years away away in the constellation Boötes.
The galaxy was discovered by America astronomer Lewis Swift using a 40.64 cm (16 inch) refractor on the 21st April 1887.
http://astronomy.activeboard.com/t57351692/ngc-5933/