Recent Positive Asteroid Occultations

HISTORY: I first used the predictions made by Gordon E.Taylor (NAO) who published events for amateurs in the BAA Handbook. The European Asteroidal Occultation Network (EAON, R. Boninsegna / E. Goffin) continued to supported my interest with yearly predictions by post. Observations were made visually with an 8" F/6 Newtonian magnification x48 + stopwatch and tape-recorder to a time accuracy of 0.5 sec using the "TIM" speaking clock. Most reports were negative - nothing seen. We are attempting to observe an asteroid passing in frony of a star. We see the star dissappear for a few seconds. This is recorded.

In 1990 I built a Philips low-light video camera kit helped by Andrew J. Elliott (Assistant Director of the BAA Asteroid and Remote Planets Section 1990-2010). The camera was mounted a-focally to a 2nd generation Micro Channel Plate (MCP) image intensifier in a DIY housing and used on my 8" F/6 Newtonian. The MCP was advertised for sale (possibly failed military spec) and three were bought in abt 1991 (£250 ea). One each for the writer, aje and Denis Buczynski. The Philips camera and MCP were replaced in 2005 with a WAT 120N+. Recordings were being made on VHS tape with a Mitsubishi TDG (Time-Date-Overlay) up to 2001. But this had the Millennium date bug so a VOLTEC TDG was purchased from MAPLIN. Both time overlay units were manually sychronised to UT by reference to an MSF LED pulse which was recorded at the start and end of the observation. This method of timing continued up to March-2010.

My first observed occultation was (130) Elektra on 2010-Feb-20 using a Meade LXD55 SN8,WAT 120N+ camera and SONY digital tape recorder. Soon after I acquired the Blackboxcamera GPSBOXSPRITE gps time-text-overlay which replaced the manual sync VOLTEC unit. Then in 2014 I purchased the more sensitive WAT-910HX/RC with recording to my now old SONY camcorder which could uploaded the recordings to PC via fire-wire on my Windows 7 Novatech laptop.

Update: From 2019-Nov-30, the OTA is a Celestron 11 on EQ6Pro working at about F5.6. Then from January 2020, I began using the USB3 QHY174m-GPS camera for recording occultations to W10 laptop. The WAT-910HX video is the more sensitive detector and reserved for more demanding events, but is less convenient to control. In the last few years there has been a collaboration ( lucky-star ) to which amateurs can send observations of special interest.

Bar Graph: The proportion in green are the +ve events.
Planetary satellites are in yellow: Titan/28Sgr in 1989 July, and Triton in 2017 Oct.

Table:
Colour code to exposure times: Blue = with a 300mm F4 reflector, Yellow = with a 203mm F4 Schmidt Newtonian, Red = C11 SCT at F/5.6
dM = drop in magnitudes, from (Asteroid+Star) to Asteroid. From April 2020 the QHY174m-GPS was being used "qhygps" in place of WAT910HX

Date	Body	Prediction	Link to report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop dM	Exposure	Light curve	Chords
Feb 20	(130) Elektra		Report	10.7	16.2 s	11.5 / 12.2	0.9	0.16		Chords
Mar 01	(532) Herculina		Report	5.8	23.0 s	10.0 / 8.9	0.33	0.64		One observer
Jun 05	(80) Sappho		Report	6.72	8.1 s	10.7 / 11.7	1.4	0.16		Chords
Oct 31	(213) Lilaea	Track Track-2	Report	7.1	5.9 s	10.8 / 12.8	2.2	0.64		One Observer

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5 Positive Events 2011:

Date	Body	Prediction	Link to report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop	Exposure	Light curve	Chords
Feb 15	(106) Dione		Report	21.76	36.6	12.7 / 12.3	0.6	0.32		Chords
May 03	(42) ISIS		Report	1.76	4.6 s	11.5 / 13.3	2.0	0.16		Chords
Sep 14	(48) Doris		Report	14.40	16.3 s	12.3 / 11.2	0.3	0.32		Chords
Nov 25	(83) Beartrix		Report	3.84	8.1 s	13.0 / 12.2	0.4	0.16		Chords
Dec 18	(1796) Riga		Report	3.44	8.6 s	11.9 / 16.0	4.1	0.16		Chords

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1 Positive Event 2012:

Date	Body	Prediction	Link to Report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop	Exposure	Light curve	Chords
Feb 23	(41) Daphne		Report	13.6	22.1 s	12.3 / 11.6	0.5	0.16
-	-	-	-	-	-	-	-	-	-	-

Positive Events 2013 - NONE

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4 Positive Events 2014

Date	Body	Prediction	Link to Report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop	Exposure	Light curve	Chords
Jan 17	(56) Melete		Report	1.2	10.2 s	12.0 / 13.1	1.4	0.16
Apr 18	(386) Siegena		Report	13.8	14.6 s	12.6 / 13.0	(r) 0.9	0.16		One observer
Apr 18	(241) Germania		Report	NEG	8.5 s	11.9 / 13.7	2.1	0.16
Sept 02	(391) Ingeborg		-	2.2	2.7 s	12.4 / 12.6	0.9	0.16		Recorded by Adrian Jones

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Date	Body	Prediction	Link to Report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop	Exposure	Light curve	Notes
Feb 16	(423 ) Diotima			29.2	30	13.0 /11.9	0.5	0.16s		8" LXD55
May 23	(583) Klotilde			1.8	7.2	9.0 / 13.5	3.5	0.08s
Aug 09	(107) Camilla			18.9	22.9	14 / 12.8	0.4	0.08s
Oct 10	(268) Adorea			3.1	3.7	14 / 12.3	1.5	0.08s

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5 Positive Events 2017:

Date	Body	Prediction	Link to Report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop	Exposure	Light curve	Notes
Feb 07	(690) Wratislavia			8.4	14.7	12.8/13.1	0.7	0.32
Sep 24	(31) Euphrosyne			7.4	12.2	12.7/11.6	0.3	0.04
Oct 05	TRITON UTube			142	160	12.7/13.5	1.4	0.64
Nov 19	(18) Melpomene			2.64	5	12 / 12.8	0.7	0.04
Nov 28	(377) Campania			8.4	9	12 / 13	0.2	0.04

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8 Positive Events 2018:

Date	Body	Prediction	Link to Report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop(r)	Exposure	Light curve	Chords/Notes
April 21	(130) Elektra			16.4	20	11.6 / 12.9	1.5	0.04
May 05	(74) Galatea			7.42	9.5	12.9 / 13.4	0.8	0.08		OW observer chart Euraster.net chords
Sep 06	(238) Hypatia		Additional Notes	12.0	13.4	11.2 / 11.9	1.2	0.16		Strong twilight (Sun at -7 deg). Combined Mag 10.7, Barlow x2 used. Frame
Sept 23	(2875) Largerkvist		Additional Note	0.60	1.0	11 / 16	0.4 Double Star Comes	0.08	Frame
Sept 26	(1573) Vaisala			0.68	1.0	12 / 13	2.2	0.08	Frame	Shift indicated - only one observation in Moonlight
Oct 20	(27561) 2000 KJ1		Three observers got chords across this 20km object. The preliminary Occult profile is elongated.	2.12	2.0	13 / 17	4.0	0.16
Oct 29	(156) Xanthippe		The best UK event of 2018 with 14 observers positive following an alert to BAA members.	5.70	7.0	12 / 14	2.3	0.04
Nov 02	(137) Maliboea		In strong twilight	4.64	6.0	12.6 / 13	0.5	0.16

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9 Positive Events 2019:

Date	MInor Planet	Prediction	Report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop	Exposure	Light curve	Chords (credit: E. Frappa)
Feb 12	(334) Chicago		W25 red filter used in error.	7.68	12 s	11.8 / 13.0	1.5	0.16
March 8	(1093) Freda		Laptop bat. failed so used a camcorder.	8.64	13 s	13.2 / 14.0	1.0	0.32
April 2	(554) Paraga			8.6	8.1s	13.9 / 12.6	0.2 small mag. drop	0.16
May 20	(671) Carnegia			1.8	2.0s	11 / 16	5.1	0.08
Jul 22	(580) Selene		The mount was moved 4m East to avoid a tree. Long exposure and low altitude of 13 deg. Report	0.9	3.0s	12 / 15	dM 2.7	0.32	At 13deg elevation
Jul 26	(489) Comacina		Poor weather forecast for this favourable event. Sky cleared 1hr before commencement Report youtube	11.06	10.0s	11 / 13	dM 2.2	0.04s		Chords
Jul 28	(586) Thekla		Low altitude and noisy data. Lucky to record this at mag 13 in passing cloud. Report	8.0s	10.0s	13 / 14.5	dM 1.2	0.64s	AOTA	Chords
Nov 07	(563) Suleika		The small magnitude difference of only 0.1 made this a difficult observation. A small dip was recorded in the light curve =>	10 +/- 1s	14 s	14 / 11	dM 0.1 small mag. drop	0.16 s		FIRST Positive event from Steeple Aston - hooraa !
Nov 30	(105) Artemis		# 9 Using C11 at F4	11.2 s	12.1 s	13.5 / 13.5	dM 0.7	0.16 s		SECOND Positive event from SA. Usng a C11

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5 Positive Events 2020:

Date	Body	Prediction	Report	Observed duration	Maximum duration	Magnitude Star / Astrd	Magnitude drop	Exposure	Light curve	Notes
Mar 12	(996) Hilaritas		Single frame D-R	0.2 Quite likely +ve, but NOT confirmed	2 s	12.9 / 14	3.7	0.2 s
Apr 15	(6723) Chrisclark		Cloud stayed away until the last min. The D event was recorded in cloud and the R was uncertain	1.25 +/- 0.4	1.4 s	10 / 17	7.4	0.1 s qhygps		An observation from the Netherlands confirmed I had observed the same chord.
Jun 25	(121) Hermione		Observed at low elivation of 8 degress in the SE. A pole caused the shadow at start of recording.	7.5 +/- 1.1	14 s	11 / 12	0.3	0.64 s qhygps		chords
Sep 27	(110989) 2001US197		unexpected +ve	0.75 +/- 0.1	0.9 s	12 / 19	7	0.1 s qhygps
Nov 11	(70008) 1998 XA53		two chords from UK	1.30 +/-0.2	1.4 s	13 / 18	4	0.4 s qhygps difficult conditions

Positive Events 2021:

Date	Body	Prediction	Report	Observed duration	Maximum duration	Mag. Star / Astrd	Mag. drop	Exposure	Light curve	Notes
Jan 22	(1076) Viola			1.3 +/- 0.1	2.8 s	13.8 /14.5	0.9	0.2 qhygps
Mar 13	(1342) Brabantia		From the Pulsar observatory.	0.81 +/-0.06	1.0 s	10.3/15	5.5	0.05 qhygps
Apr 17	(103) Hera		Chords With fit to DAMIT 3D model	1.2 +/-0.3	4.0 s	13/14	0.7	0.15 qhygps
Jun 05	(2363) Cebriones		LuckyStar Uncertain in Twilight - partial event uncomfirmed.	3 ?	6 s	14.2/15.5	2.1	0.4 ghygps
Jun 10	(663) Gerlinde		Low altitude in Del. Chords Started recording just in time!	9.5 +/-0.3	12 s	14.1/14.6	1.0	0.5 ghygps
Jly 29	(212) Medea		Difficult conditions Alt/Az 23/078 in Moonlight and low mag drop. Uncertain occn.	2.0 +/- 0.5	4.5 s	14.0/15.0	0.2	0.5 qhygps		Pyote reports: possible false positive
Aug 23	(1434) Margot		S/N of 6 (good) and confirmed positive. report	3.9 +/- 0.25	5.0 s	13.6/15.0	1.4	0.2 s qhygps
Sept 20	2002GZ32		Centaur for the lucky-star campaign	27s +/- 1	32 s	13.8 / 19	5	1.0 s qhygps
Oct 06	(32) Pomona		The star and asteroid formed a pair until the separation closed up. The dip is seen in the blue light curve.	6.9 s +/- 0.2	6 s	12.5 / 13	0.3	0.1 s qhygps