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Occultations. 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 Phenomena. Total lunar occultations

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Occultations

Occultations

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 phenomena
Types of High-Speed Celestial Phenomena

  • 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
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
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 –

c:\avi07603\DeltaSco122103.avi

Graze, 1.0-mag. Spica, 37%-, w. of Delta, Utah, 2005 Dec. 25 –

c:\avi07603\Spica122505seq2.avi (8 in. SCT & PC164C) and

c:\avi07603\Spica_50mm122505_3.avi

c:\graze\muari612\Bob Sandy u Ari 070612\Bob . .avi


Occultations of stars by asteroids
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
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 – c:\asteroid\20071221\7FTALR41.asf

Later – Dike events, c:\avi\mp99xxx.avi


1999 leonids lunar impacts recorded nov 18 with 5 telescope at mt airy md
1999 Leonids Lunar Impactsrecorded Nov. 18 with 5” telescope at Mt. Airy, MD


Leonid Lunar ImpactRecorded 2001 Nov. 18, 23:19:15 UT, Laurel, MDconfirmed by Tony Cook at Arlington, VAand Roger Venable, Augusta, GA


Methods of observing high speed celestial phenomena
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 events)

  • 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 ObservationNote on telescope box, WWV receiver (Timekube), GPS receiver, eyepiece, tape recorder, cell phone


Items for video observation
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 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 12 volt battery optional f 6 3 focal reducer
Cheap Video SystemPC-23C, RCA TV/VCR combo, small 12-volt battery, optional f/6.3 focal reducer


Compact Video SystemWatec 902h, Meade f/3.3 focal reducing lens, small 12-volt battery (not shown), camcorder



Www pfdsystems com
www.pfdsystems.com

Robust GPS video time insertion using the 1PPS signal from a

Garmin 18 LVC GPS receiver


Station b sony digital camcorder
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!



The pleiades recorded with the 8x50 finder system
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

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
Path across Texas; total occultation is south of path

Our expedition 

Rick 

Frankenberger


Path near waller hockley texas us 290 area
Path near Waller & Hockley, Texas (US 290 area)

A

meet

Area shown in detail

in next slide

Hockley

Offsets are -0.7 and -1.7


Details of hegar rd imhof rd sites used n of hockley texas
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

R. Sandy

met

D. 

Stockbauer

D. Dunham S. remote


Light curve from bob sandy s video recording of the 2007 june 12 th grazing occultation of arietis
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 June 12

Star  Arietis (ZC 399) observed in Texas and Louisiana,

2007 June 12





Remote stations for asteroidal occultations
Remote Stations for Asteroidal Occultations June 12

  • 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




Please do not disturb 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
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 more stations

In c:\avi\mp99*.avi


Klotilde occultation
Klotilde occultation more stations


May 8 th graze
May 8 more stationsth graze


May 12th graze
May 12th graze more stations


Oct 6th graze
Oct. 6th graze more stations


For more information about iota and observing occultations
For More Information about IOTA and observing occultations: more stations

  • 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 site

  • http://www.asteroidoccultations.com - asteroidal occultation updates

  • 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