ASTEROID OCCULTATIONS I HAVE OBSERVED

Last updated 8/22/10

What does an asteroid occultation look like? Using video we can get a good idea. We consider the occultation of a 7.6 magnitude star SAO 060107 by the 76 km diameter asteroid known as (516) Amherstia. I travelled to Atlantic Beach, Florida on 14 January 2002 in order to capture this using a Collins Electro Optics image intensifier, Watec low light surveillance camera, attached to a Celestron 8 Schmidt- Cassegrain telescope. The seeing was not perfect but the occultation was clearly observed.

The first image below shows the "target star -- the brightest one in the field of view -- with the tiny image of the asteroid just to the upper right and almost appearing to touch it. This frame was taken 40 minutes before central occultation. The asteroid is magnitude 12.3. Visually, it would be easy to time the occultation of the star, but the asteorid would be too dim to detect in a typical sky condition.

amh1s.jpg (5KB)

Several minutes before central occultation, the asteroid is now immersed in the glare of the bright star.

amh2s.jpg (5KB)

Then the asteroid passes in front of the star causing a vast reduction in the star's brightness. Notice, however, that you can actually see the asteroid by itself in place of the star.

amh3s.jpg (5KB)

Finally the star regains full brilliance after the completion of the occultation.

amh4s.jpg (5KB)

p1207a1 (4k)

My system attached to Tony White's (Tulsa, OK) Celestron 11. Arrow points to the connected unit from the SCT back of the C11. First, the f/3.3 focal reducer attached to the Collins I3, then the tiny Watec 902H.Photo taken 12/20/07 by Tony White.

gpcu1a (4k)

For occultations of bright stars I use a 100mm f/2 Nikon lens and a light sensitive camera such as a Watec or PC164. This photo was taken at Varadero, Cuba March 15, 2008 after the successful occultation of a 6.3 magnitude star by the asteroid 241 Germania. Photo by Lynn Palmer

TABLE OF PERSONALLY OBSERVED ASTEROID AND SOLAR SYSTEM BODY OCCULTATIONS

I have successfully observed and timed the following asteroid/planetary satellite occultations. However, you may ask why there is such a paucity of successes. Accurate ground track forecasting prior to 2001 was really poor, making successful observations problematic at best. You had to be really lucky in order to see an occultation. Beginning in 2001 many more events were being forecasted with improved accuracy, and astrometry (the science of astronomical position measurement) sources and reduction techniques experienced a major advancement. C8=Celestron 8-inch Schmidt Cass telescope in the table below. The M4 is the Meade 2045D telecope.

minisetup (4k)

Using the above setup I have recently started deploying more than one station when the occulted target star brightness allows (magnitude brighter than 9.6). This portable design, created by Scott Degenhardt, is the most productive tool so far for multi-station asteroid occultation monitoring. In the table it is referred to as "50mm mini". I have also started to use its larger cousin the 80mm midi.

NO. DATE ASTEROID/Solar System Body STAR METHOD SITE
115 8/21/10 (16) Psyche HIP 22112 50mm Mini (2) CLEBURNE, TX
114 8/14/10 (404) Arsinoe TYC 1340-02164-1 C8 INTENSIFIED VIDEO REFUGIO, TX
113 5/16/10 (276) Adelheid 2UCAC43762516 C11 INTENSIFIED VIDEO HOUSTON, TX
112 3/29/10 (52) Europa 2UCAC 39108118 C11 INTENSIFIED VIDEO HOUSTON, TX
111 2/14/10 (56) Melete UCAC2 36090877 C8 INTENSIFIED VIDEO HOUSTON, TX
110 2/5/10 (191) Kolga TYC 5636-00417-1 20inch + 80mm Midi SIERRA VISTA, AZ
109 12/25/09 (81) Terpsichore TYC 1795-00251-1 50mm Mini (2) PATTERSON, CA
108 12/24/09 (216) Kleopatra TYC 4909-00873-1 80mm Midi(2) CASA GRANDE, AZ
107 12/6/09 (423) Diotima TYC 1252-00803-1 C9.25 KINGMAN, AZ
106 12/6/09 (455) Bruchsalia TYC 4682-02550-1 C9.25 KINGMAN, AZ
105 12/6/09 (348) May TYC 5836-00670-1 C9.25 KINGMAN, AZ
104 11/21/09 (234)Barbara HIP 34106 50mm Mini(5) POLK CITY, FL
103 10/24/09 (164)Eva HIP 10015 50mm Mini LOXLEY, AL
102 9/24/09 (579)Sidonia TYC 5273-00531-1 C8+80mm Midi(2) EASTLAND WA
101 8/20/09 (240)Vanadis HIP75848 75mm Mini NOME TX
100 6/6/09 (46)Hestia TYC 6184-00208-1 C8 VISUAL CLEMVILLE TX
99 2/17/09 (185)Eunike TYC 0193-00670-1 50mm mini (2) QUINCY NM
98 2/7/09 (654)Zelinda UCAC2 32019943 M8 INTENSIFIED VIDEO MADILL OK
97 2/3/09 (366)Vincentina UCAC2 42749694 C8 INTENSIFIED VIDEO HOUSTON TX
96 12/25/08 (751)Faina TYC 5267-00645-1 C8 INTENSIFIED VIDEO NAVASOTA TX
95 12/8/08 (402)Chloe UCAC2 35357625 C11 INTENSIFIED VIDEO LIBERTY TX
94 11/27/08 (304)Olga UCAC2 26590394 M8 INTENSIFIED VIDEO ENID OK
93 11/15/08 (1149)Volga TYC 0543-01301-1 C8 INTENSIFIED VIDEO HOUSTON TX
92 9/12/08 (9)Metis HIP 14764 105mm FL VIDEO LAS VEGAS NV
91 8/24/08 (111)Ate TYC 5803-01587-1 M8 INTENSIFIED VIDEO BRUDERHEIM, ALBERTA, CA
90 6/18/08 (19)Fortuna TYC 6276-01878-1 C11 INTENSIFIED VIDEO BEEVILLE TX
89 6/12/08 (47)Aglaja UCAC2 19792163 C8 INTENSIFIED VIDEO MAXWELL CA
88 4/8/08 (667)Denise TYC 1401-00822-1 M4 INTENSIFIED VIDEO HORSESHOE BAY TX
87 3/15/08 (241)Germania HIP 17026 100mm/fl VIDEO VARADERO CUBA
86 3/11/08 (735)Marghanna TYC 2936-00356-1 M8 INTENSIFIED VIDEO WINK TX
85 2/28/08 (429)Lotis TYC 0191-00729-1 M8 INTENSIFIED VIDEO GARDEN CITY TX
84 1/22/08 (13)Egeria TYC 0026-00627-1 C11 INTENSIFIED VIDEO CASA GRANDE AZ
83 1/12/08 (70)Panopaea TYC 2501-00817-1 11MAK INTENSIFIED VIDEO CRYSTAL NV
82 1/2/08 (24)Themis UCAC2 38791508 24CASS INTENSIFIED VIDEO CANEY OK
81 12/20/07 (187)Lamberta TYC 2416-00772-1 C11 INTENSIFIED VIDEO DEWEY OK
80 11/10/07 (15)Eunomia TYC 1930-00091-1 M4 INTENSIFIED VIDEO CALLAGHAN TX
79 11/05/07 (137)Meliboea TYC 5739099761-1 C11 INTENSIFIED VIDEO ANGLETON TX
78 10/26/07 (203)Pompeja TYC 1410-00470-1 M4 INTENSIFIED VIDEO FOREST LAKE MN
77 9/09/07 (704)Interamnia TYC 2410-00061-1 C8 INTENSIFIED VIDEO BERNALILLO NM
76 8/29/07 (409)Aspasia TYC 1327-00077-1 C8 INTENSIFIED VIDEO SWEENY TX
75 7/20/07 (153)Hilda UCAC2 25791797 M10 INTENSIFIED VIDEO OTHELLO WA
74 7/16/07 (225)Henrietta TYC 1065-00745-1 C11 INTENSIFIED VIDEO LAST CHANCE CO
73 7/10/07 (125)Nausikaa HIP 92988 M4 INTENSIFIED VIDEO CALLAHAN, FL
72 6/25/07 (125)Nausikaa TYC 7427-02638-1 M4 INTENSIFIED VIDEO WICKENBURG, AZ
71 4/18/07 (411)Xanthe HIP 43103 100mm INTENSIFIED VIDEO GREEN COVE SPRINGS, FL
70 4/15/07 (494)Virtus UCAC2 42210347 C8 INTENSIFIED VIDEO CORDELE, TX
69 2/18/07 (55)Pandora TYC 1421-00289-1 M4 INTENSIFIED VIDEO ENNIS, TX
68 1/10/07 (44)Nysa TYC 1323-00422-1 M4 INTENSIFIED VIDEO LIBERTY CITY, TX
67 1/3/07 (51)Nemausa HIP 48681 M4 INTENSIFIED VIDEO FAUCETT, MO
66 12/22/06 (547) Praxedis TYC 4822-02645-1 C8 INTENSIFIED VIDEO TRAVIS, TX
65 12/14/06 (70) Panopaea TYC 1231-01469-1 C8 INTENSIFIED VIDEO MADISONVILLE, TX
64 11/26/06 (422) Berolina 2UCAC 42542715 M8 VISUAL TONKAWA, OK
63 11/26/06 (601) Nerthus TYC 5764-01407-1 M8 INTENSIFIED VIDEO COLWICH, KS
62 11/22/06 (103) Hera TYC 0040-00819-1 C8 INTENSIFIED VIDEO CENTERVILLE, TX
61 11/21/06 (302) Clarissa TYC 1817-01424-1 C8 INTENSIFIED VIDEO (VISUAL OFF SCREEN) LAKE JACKSON, TX
60 10/3/06 (25) Phocaea HIP 115725 M10 INTENSIFIED VIDEO WOODSTOWN, NJ
59 7/12/06 (444) Gyptis TYC 5109-00140-1 C8 INTENSIFIED VIDEO ANGLETON, TX
58 6/24/06 (35) Leukothea UCAC2 16455768 C11 INTENSIFIED VIDEO BOULOGNE, FL
57 5/27/06 (702) Alauda UCAC2 13791670 C8 INTENSIFIED VIDEO LIVINGSTON, LA
56 4/30/06 (580) Selene TYC 4973-01378-1 C8 INTENSIFIED VIDEO COLETOVILLE, TX
55 3/12/06 (602) Marianna HIP 90871 M 4 INTENSIFIED VIDEO ABILENE, TX
54 2/24/06 (530) Turandot HIP 40832 M 4 INTENSIFIED VIDEO CINCINNATI, OH
53 2/10/06 (134) Sophrosyne TYC-2926-01789-1 36-INCH REFLECTOR INTENSIFIED VIDEO HOUSTON, TX
52 2/05/06 (764) Gedania UCAC2-35203988 M 4 INTENSIFIED VIDEO PENITAS, TX
51 1/28/06 (490) Veritas TYC-0736-00356-1 M 4 INTENSIFIED VIDEO KEENANSVILLE, NC
50 1/14/06 (173) Ino TYC-0145-00077-1 M 4 INTENSIFIED VIDEO LINN, TX
49 1/5/06 (466) Tisiphone TYC-1371-00938-1 C8 INTENSIFIED VIDEO TELFERNER, TX
48 12/11/05 (28) Christine UCAC2-37141382 C8 INTENSIFIED VIDEO HOCKLEY, TX
47 12/03/05 (52) Europa TYC 4974-00584-1 M 4 INTENSIFIED VIDEO LAKE HAVASU CITY, AZ
46 12/01/05 (162) Laurentia TYC 1799-00077-1 C8 INTENSIFIED VIDEO BUFFALO, TX
45 11/15/05 (345) Tercidina TYC 05227-00241-1 C8 INTENSIFIED VIDEO WEIMAR, CA
44 10/28/05 (790) Pretoria TYC 0216-01594-1 M 4 INTENSIFIED VIDEO CATOOSA, OK
43 10/7/05 (1082) Prirola TYC 1311-2375-1 C8 INTENSIFIED VIDEO HOUSTON, TX
42 8/13/05 (893) Julia HIP 7948 7x35mm VISUAL PENSE, SASKATCHEWAN, CANADA
41 7/11/05 (103) Hera TYC 1210-01821-1 C8 INTENSIFIED VIDEO SENTINEL, AZ
40 6/13/05 (103) Hera TYC 6264-00003-1 C8 INTENSIFIED VIDEO GALVESTON ISLAND, TX
39 5/17/05 (54) Alexandra TYC 7902-01828-1 M 8 INTENSIFIED VIDEO ACUFF, TX
38 1/18/05 (216) Kleopatra UCAC 32014147 C8 INTENSIFIED VIDEO HOUSTON, TX
37 10/29/04 (8) Flora TYC 1367-00024-1 M 4 INTENSIFIED VIDEO OROGRANDE, NM
36 10/07/04 (8) Flora TYC 1351-00528-1 C8 INTENSIFIED VIDEO CLINTON, BC CANADA
35 9/05/04 (107) Camilla TYC 5244-00017-1 C8 INTENSIFIED VIDEO FOUNTAIN HILLS, AZ
34 8/25/04 (11) Parthenope TYC 6859-01200-1 C8 INTENSIFIED VIDEO ALVIN, TX
33 7/18/04 (41) Daphne TYC 0531-02020-1 C8 INTENSIFIED VIDEO FRIENDSWOOD, TX
32 7/3/04 (64) Angelina TYC 1215-01306-1 C8 INTENSIFIED VIDEO KRAMER JUNCTION, CA
31 6/30/04 (522) Helga TYC 6310-01494-1 C8 INTENSIFIED VIDEO INYOKERN, CA
30 12/31/03 (208) Lacrimosa TYC 1397-01764-1 C8 INTENSIFIED VIDEO SPLENDORA, TX
29 12/14/03 (231) Vindobona TYC 2389-01522-1 C8 INTENSIFIED VIDEO MOUNTAINAIRE, AZ
28 12/07/03 (115) Thyra TYC 5769-00278-1 C8 INTENSIFIED VIDEO ARIZONA CITY, AZ
27 10/24/03 (978) Aidamina HIP 106841 C8 INTENSIFIED VIDEO TX,NM BORDER
26 8/1/03 TITANIA TYC 5806-696-1 36INCH REFLECTOR VIDEO BRAZOS BEND, TX
25 7/29/03 (654) Zelinda TYC 6285-03426-1 C8 INTENSIFIED VIDEO STILLWELL, OK
24 6/18/03 (85) Io TYC 0530-01006-1 C8 INTENSIFIED VIDEO HOUSTON, TX
23 3/23/03 (704) Interamnia HIP 36189 M12 VIDEO KONA, HI
22 1/15/03 (95) Arethusa TYC 0191-00774-1 C8 VISUAL MCCOOK, TX
21 1/3/03 (726) Joella TYC 4848-02317-1 C8 INTENSIFIED VIDEO CASH, TX
20 1/1/03 (233) Asterope TYC 0726-00419-1 C8 INTENSIFIED VIDEO SANTA FE, TX
19 11/14/02 (350) Ornamenta TYC 0111-01007-1 C8 INTENSIFIED VIDEO ODEM, TX
18 8/13/02 (688) Melanie TYC 5236-00201-1 C8 INTENSIFIED VIDEO HOUSTON, TX
17 5/24/02 (102) Miriam TYC 6252-01873 C8 INTENSIFIED VIDEO RIO RICA, AZ
16 4/20/02 (139) Juewa TYC 6148-00023 C8 INTENSIFIED VIDEO OAK RIDGE, CA
15 3/27/02 (654) Zelinda TYC 0168-02620 C8 INTENSIFIED VIDEO VIOLA, KS
14 1/14/02 (516) Amherstia SAO 060107 C8 INTENSIFIED VIDEO ATLANTIC BEACH, FL
13 9/8/01 TITANIA ZC 3167 C14 VISUAL BARQUISIMETO, VENEZUELA
12 10/31/01 (48) Doris TYC1315-01463-1 17-INCH REFLECTOR VISUAL HOUSTON, TX
11 12/4/97 (105) Artemis SAO 134036 C8 VISUAL PHOENIX, AZ
10 12/17/96 (704) Interamnia BD+3 633 C8 VISUAL PHOENIX, AZ
9 10/9/93 (27) Euterpe PPM 174714 C8 VISUAL DUMAS, TX
8 1/3/91 (4) Vesta SAO 93228 C8 VIDEO LAPEER, MI
7 4/11/85 (129) Antigone BD+20 2390 C8 VISUAL PARKER, CO
6 5/29/83 (2) Pallas 1 Vulpeculae C8 VISUAL SPLENDORA, TX
5 4/26/83 (52) Europa BD+21 1797 C8 VISUAL HOUSTON, TX
4 11/15/82 (375) Ursula SAO55791 C8 VISUAL WINNIE, TX
3 10/7/81 (88) Thisbe SAO 187124 C8 VISUAL CHEYENNE, WY
2 12/11/79 (9) Metis SAO 80950 5R VISUAL GEORGETOWN, GUYANA
1 3/5/77 (6) Hebe Gamma Ceti 5R VISUAL VICTORIA, TX

Some instruments I use include the 50mm mini, 80mm midi and 120mm maxi. Each is chosen based on the limiting magnitude of the target star.

120mm (4k)

The 120mm maxi scope is an f/5 refractor mounted in an alt-az configuration

midi (4k)

The 80mm midi is also an f/5 refractor mounted on a tripod. Note that all instruments are spray painted black.

boxofstuff (4k)

Support equipment include the camcorder, battery, KIWI GPS unit, VCR timer and associated cables.

My method of observation changed in 2001 when I purchased a red sensitive 3rd generation image intensifier from Collins Electro Optics. This remarkable device is vastly superior to either visual or video observation alone. But for general occultation observation of stars down to +10, for example, intensification is really not needed. I use it because it improves the chances for faint star detection in the event that the target is between +11 and +12. In a star field crowded with dim stars, or in a case where the target is a close double, the intensifier makes a vast difference. Recall that visual observation has built in human reaction time as well as the inability to play the observation back to check its accuracy and show it to others.

For each success listed in the table, there were at least 7 to 10 failures that are not listed in the years prior to 2001. Following that the failure rate decreased to 1 in 2. The encouraging thought here is that if you make an attempt and do not succeed the first time, continue to observe future events. You will increase your proficiency in recognizing the problems associated with finding the target star, tracking, observing for a continuous period of time, battling weather elements, battery failures and more. Paying close attention to the predictions will let you become familiar with the error margins and will also lead to more successes. This is a fun and fantastic experience.

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