[] Occultations with Video

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Transcript [] Occultations with Video

2008 April 13,
Northern Virginia Astronomy Club meeting
David W. Dunham, IOTA
Adopted from a similar talk given at the
2007 Virginia Association of Astronomical Societies, Crockett
Park, 2007 Oct. 6
Types of High-Speed Celestial
Total lunar occultations
Lunar grazing occultations
Planetary occultations
Asteroidal occultations
Occultations by comets, natural satellites,
and trans-Neptunian objects
• Lunar meteor impacts
IOTA = International Occultation
Timing Association
• Occult – Latin for “to cover” – one astronomical
body by another
• Lunar occultations of stars are most common
• Timings used to be used to determine longitude and the
lunar orbit (now by laser ranging)
• Then they were used to refine astrometric data until
Hipparcos data did most of that job better
• Now timings used to map lunar profile, useful for solar
eclipse analysis & possible polar ice deposits (there’s new
interest in grazes to refine the polar region data of lunar
digital elevation models that will be used for planning
observations by Lunar Reconnaissance Orbiter and other
lunar missions that will be launched in the next few years)
• Many close double stars discovered during occultations;
some stellar angular diameters measured
Lunar Profile from Graze of delta Cancri – 1981 May 9-10
Circled dots are Watts’ predicted limb corrections
Grazing Occultation Videos
Graze, 5.7-mag.  Arietis, Moon 10%-, Hockley, Texas,
2007 June 12 – c:\avi07626\MuArietis_N station.avi
Graze, 2.5-mag. close double star  Scorpii, 8%+,
Rockaway Beach, New York City, 2003 Dec. 21 –
Graze, 1.0-mag. Spica, 37%-, w. of Delta, Utah, 2005 Dec. 25 –
c:\avi07603\Spica122505seq2.avi (8 in. SCT & PC164C) and
c:\graze\muari612\Bob Sandy u Ari 070612\Bob . .avi
Occultations of Stars by Asteroids
• Difficult to predict; 1st seen in Sweden in 1958
• As orbits & astrometric techniques improved,
more observed in mid to late 1970’s
• Predictions considerably more accurate in 1997
with release of Hipparcos space astrometry data
• Observations determine the sizes, shapes,
satellites, and accurate positions of the asteroids
• Accurate orbits allow mass determinations from
measuring perturbations of the orbits
• Very close double stars and stellar angular
diameters resolved
• Geometry shown in next figure
• More distant objects (Trojans, Centaurs, TNO’s)
harder to predict but more valuable
Asteroidal Occultation Videos
Occultation of Regulus by (166) Rhodope, Montestirio, Spain,
2005 October 19 with 50mm telephoto lens – c:\avi\mp166reg.avi
Occultation of 9.5-mag. Star by Alstede, Oraville, MD, 2005
November 26 with 8-in. SCT & PC164C & f/3.3 focal reducer
Grazing occultation of 6.7-mag. Star by Thusnelda, Runyon, FL
2007 Dec. 18 with 4” Meade & Collins I3 image intensifier –
Later – Dike events, c:\avi\mp99xxx.avi
1999 Leonids Lunar Impacts
recorded Nov. 18 with 5” telescope at Mt. Airy, MD
Leonid Lunar Impact
Recorded 2001 Nov. 18, 23:19:15 UT, Laurel, MD
confirmed by Tony Cook at Arlington, VA
and Roger Venable, Augusta, GA
Methods of Observing High-Speed
Celestial Phenomena
• All methods need UTC time base (from VNG
before shutdown, WWVH, WWVB, GPS, etc.)
• Visual, eye-and-ear
• Visual, stopwatch (with assistants for multiple
• Visual with tape recorder
• Video, least expensive system
• Video, airplane transport
• High-speed photoelectric systems
• CCD systems (drift scan method)
• Remote sites (record more chords)
Visual Observation
Note on telescope box, WWV receiver (Timekube),
GPS receiver, eyepiece, tape recorder, cell phone
Items for video observation
PC164C camera, $130, www.supercircuits.com
PA3 microphone & tab adaptor
12-volt battery & video connector
1.25” to C – adaptor, $35, Adirondack video
RCA cable, Radio Shack
• For SCT’s, recommend Meade f/3.3 focal reducing lens
• Input-capable camcorder or portable 9-in. TV/VCR combo
unit (Sylvania unit on amazon.com for under $100 US)
• Shortwave radio, WWV at 5 & 10 mHrtz, Radio Shack
• GPS video time inserter (Kiwi has best error checking)
• In USA, Europe, & Japan, GPS time can be checked with
clocks that set themselves with long-wave time signal
(WWVB in USA, DCF77 in Europe)
The New Sensitive Cameras
• The Watec 902H camera is over 4 years old, costs about $300, and has
been discussed at ESOP by A. Elliott and E. Bredner. It is excellent,
seeing more than you can with an eyepiece, & is a little noisy.
• The PC164C, from www.supercircuits.com since 2001 Dec., has the
same CCD chip as the Watec but 1/3rd inch rather than ½ inch; it is
almost as sensitive with a 2/3rds smaller field, but at $130, it is less
than half the price. It seems to be a little less noisy than the Watec.
• A small adapter tube from Adirondack Video for $35 screws into these
cameras (C-mount) so they can be used with any 1.25-in. eyepiece
holder, only about 1 inch long, the PC164C is 2 inches long and light.
• I believe there is a PAL version of the PC164C, but if it is hard to get,
a similar camera for a similar price, CCTV Camera’s Model 2006X
costs 69 pounds, with the same CCD chip as the PC164C. This British
camera is PAL; see www.rfconcepts.co.uk/cctv-camera.htm .
• These cameras allow accurate timing of fainter star lunar grazes and
asteroidal occultations, the latter especially important since visual
timings of them have larger errors; there are more opportunities!
• Focal reducing lenses, esp. f/3.3 Meade, give much larger FOV.
Cheap Video System
PC-23C, RCA TV/VCR combo, small 12volt battery, optional f/6.3 focal reducer
Compact Video System
Watec 902h, Meade f/3.3 focal reducing lens, small 12-volt
battery (not shown), camcorder
Air carry-on system (R. Nugent)
Robust GPS video time insertion using the 1PPS signal from a
Garmin 18 LVC GPS receiver
Station “B”, Sony Digital Camcorder
No Telescope, just an undriven good camcorder! I set the
Moon just outside the field, above and left, 8 min. before the
graze. This station had 5 D’s and 5 R’s, more than any other;
although it had less than 1000th the aperture of the 1m
telescope on Hokkaido, it was more successful!
Orion 8x50 finder scope video system
By Scott Degenhardt
The Pleiades recorded with the 8x50 finder system
Using PC164C camera and Mogg focal reducer, by Scott Degenhardt
Maps for the grazing occultation of
 Arietis on 2007 June 12
Showing locations of the expeditions, and of the
observers at the expedition near Hockley, Texas
Path across Texas;
total occultation is south of path
Our expedition 
Rick 
Path near Waller & Hockley, Texas (US 290 area)
Area shown in detail
in next slide
Offsets are -0.7 and -1.7
Details of Hegar Rd./Imhof Rd. sites used n. of Hockley, Texas
R. Nugent
D. Clark (2)
P. Maley
Dunham N. remote/Cudnik
D. Dunham visual
D. 
D. Dunham S. remote
Light curve from Bob Sandy’s video recording of the
2007 June 12th grazing occultation of  Arietis
Reduction Profile of Grazing Occultation of the Double
Star  Arietis (ZC 399) observed in Texas and Louisiana,
2007 June 12
2007 Oct. 17 graze of ZC 2702
2007 Oct. 17 graze of ZC 2702
2007 Oct. 17 graze of ZC 2702
Remote Stations for Asteroidal Occultations
Separation should be many km, much larger than for grazes, so tracking times
& errors are too large
Unguided is possible since the prediction times are accurate enough, to less
that 1 min. = ¼
Point telescope beforehand to same altitude and azimuth that the target star
will have at event time and keep it fixed in that direction
Plot line of target star’s declination on a detailed star atlas; I use the
Millennium Atlas
From the RA difference and event time for the area of observation, calculate
times along the declination line
Adjust the above for sidereal rate that is faster than solar rate, add 10 seconds
for each hour before the event
Can usually find “guide stars” that are easier to find than the target
Find a safe but accessible place for both the attended & remote scopes
Separation distance limited by travel time & total tape record time
Roger Venable uses VCR’s with timed starts, allows larger separation
Better to have remote sites attended for uncovering telescope (dew prevention)
and starting equipment later (allows larger separations), and security
Finder chart for occultation of 10.3-mag. star by
(1685) Toro on 2004 August 10
Finder chart for remote station for occultation by
(1685) Toro on 2004 August 10
Precisely Pointed Automatic
Astronomical Station to
Record the eclipse of the star
TYC 0483-01460-1
by the asteroid 491 Carina at
4:28 am PDT this morning
If you have any questions or concerns, call my
cell phone, 301-526-5590, I’m nearby
David Dunham,
International Occultation Timing Assoc.
Successful Remote + Attended Positive Observations
from 2 or more stations
2001 Sept. 7, 9 Metis, northern California, D. Dunham
2002 April 21, Oriola, Washington, S. Preston
2003 Jan. 17, Bathilde, Georgia, R. Venable
2004 July 1, Nanon, s. Calif., D. Dunham, but D. Stockbauer was at “remote” site, turned on recorder without
changing pointing
2004 Oct. 6, Ute, North Carolina, D. Dunham
2004 Oct. 29, Flora, New Mexico, D. Dunham
2005 Mar. 12, Bathseba, Georgia, R. Venable
2005 May 13, Dufour, New South Wales (AU), D. Gault (home “remote” & mobile)
2005 Dec. 1, Laurentia, Georgia, R. Venable
2005 Dec. 1, Dike, Maryland & Virginia, D. Dunham (3 positives, star close double)
2005 Dec. 3, Europa, California, D. Dunham
2006 Jan. 28, Veritas, North Carolina, D. Dunham
2006 Feb. 24, Turandot, Indiana, D. Dunham
2006 Feb. 26, Abnoba, Florida, R. Venable
2006 June 12, Pallas, Georgia, R. Venable (4 positives! Widest separation)
2007 Jan. 10, Nysa, Georgia, R. Venable
2007 Feb. 21, Thisbe, Florida, D. Dunham
2007 Feb. 28, Nemausa, California, D. Dunham
2007 Apr. 13, Fortuna, Virginia and N. Carolina, D. Dunham (2 +, 1 miss, my widest separation)
2007 Apr. 22, Dike, Florida, R. Venable
2007 May 24, Papagena, Maryland and Pennsylvania, D. Dunham (3 positives)
2007 Sept. 11, Senta, New South Wales (AU), D. Gault
2007 Nov. 20, Amalia, Georgia, R. Venable
2007 Dec. 18, Thusnelda, Florida, D. Dunham
2008 Jan. 14, Sicilia, Alabama, R. Venable (star close double)
2008 Feb. 10, Dynamene, North Carolina, R. Venable
Many other cases where 2 stations were run and 1 had an occ’n & the other a miss, especially by Roger Venable;
example was my observation of Rhodope occulting Regulus on 2005 October 19
The video files are
In c:\avi\mp99*.avi
Klotilde occultation
May 8th graze
May 12th graze
Oct. 6th graze
For More Information about IOTA
and observing occultations:
• http://iota.jhuapl.edu - my web site; /iotaindx.htm for items of
recent interest; /exped.htm for Mid-Atlantic occultations
• Updates by e-mail – [email protected]
• http://www.lunar-occultations.com/iota – the main IOTA web
• http://www.asteroidoccultations.com - asteroidal occultation
• http://www.poyntsource.com/New/Global.htm - asteroidal
occ’n maps, station & star lists
• http://www.asteroidoccultations.com/observations/NA Results of asteroidal occ’n observations, etc.
• http://www.pfdsystems.com – Kiwi video time inserter