[Lvas] Help us measure (135) Hertha Wed. night, s.Calif., AZ, NM, OK, AR, to Tenn.

[David Blanchette]

I, and probably a couple of others in the group, received the notice 
below about an asteroid occultation of a start, about 11:48pm, 
Wednesday December 10 (this Wednesday.)  I've posted a map at 
http://www.lvastronomy.com/asteroid.jpg, which has the red centerline 
down by Laughlin.  The width of the occultation goes a little farther 
north than Searchlight, and about the same distance south, so 
anywhere along hwy 95, south of Searchlight, would be a useful place to be.

There are a number of "off road" spots along Hwy 95, I've even 
considered a few for regular observing.

If anyone is interested in going out, please post, and contact Mr. 
Dunham with the information he wants.

-- David


At 11:51 PM 12/7/2008, David Dunham wrote:
>      Please help us measure the size and shape of the asteroid (135)
>Hertha when it occults 9.2-mag. SAO 93103 in Aries Wed. night, Dec.
>10/11, in a path with expected width 82 km extending from northern
>South Carolina (7:42 UT or 2:42 am EST Dec. 11) across s. Tenn., n.
>Ark., Okla., n. N.Mex., n. Ariz., and southern California (7:48 to
>7:49 UT Dec. 11 UT, or 11:48-11:49 pm PST Dec. 10).  The asteroid
>may occult the star for up to 15 seconds with an easily-seen 2.6-
>mag. drop.  Hertha is an M-class asteroid that could have an unusual
>shape.  Accuweather is forecasting clear skies across the path
>except for thick clouds from central Tenn. to the Atlantic coast,
>and some 40% high clouds on the central Calif. coast. A more
>detailed Astro Meteo forecast will become available starting about
>noon on Tuesday, Dec. 9.
>
>      Please let us know if you plan to try it, and from where if we
>don't already have your observing site coordinates.  We want to
>coordinate coverage of the occultation; mobile observers don't want
>to duplicate coverage by fixed-site observers.  The occultation by
>Hertha is long enough to observe visually; if possible, please try
>to time the occultation using the techniques described at
>http://iota.jhuapl.edu/timng920.htm .
>
>THE PATH
>
>      An overview of the path of the occultation can be found, along
>with finder charts of different scales to locate the target star, on
>Steve Preston's Web page for the event at
>http://asteroidoccultation.com/2008_12/1211_135_13369.htm .  The
>path crosses western Tenn. (Memphis) and n. Arkansas (Little Rock
>near the predicted s. limit) at 7:43 UT (1:43 am CST); across
>Oklahoma (Okla. City just inside the s. limit; with possible errors,
>Tulsa, just outside the n. limit, could actually have an
>occultation) at 7:44 UT; over the northern Texas panhandle at 7:45
>UT; across n. New Mexico (Santa Fe; Albuquerque just s. of the s.
>limit could have an event) at 7:46 UT (12:46 am MST); n. Arizona
>(Flagstaff) at 7:47 UT Dec. 11; across southern Calif. (Mojave
>Desert and Valencia, with an occultation possible as far south as
>Los Angeles or as far north as Bakersfield) at 7:48 UT (11:48 pm
>PST Dec. 10); and over the s.w. Pacific coast (Santa Maria and San
>Luis Obispo) at 7:49 UT.  You can see the path in more detail using
>Derek Breit's interactive Google maps at
>http://www.poyntsource.com/New/Global.htm
>
>THE STAR
>
>      This star could be monitored with a 3-inch telescope, but
>with the 97% sunlit Moon in the northern Pleiades only 15 deg. from
>the target, a 4-inch or larger telescope is recommended.  The star
>will be relatively high in the western sky, from 55 deg. on the
>Calif. coast to 29 deg. in central Tenn.  SAO 93103, a spectral type
>F8 star, is at J2000 RA 2h 47m 24.2s, Dec +19 deg. 50' 39", roughly
>between the Pleiades and Hamal (closer to the latter and s.e. of
>it), just over a deg. east of 6th-mag. mu Arietis, and forming a
>pair with a slightly brighter star about 4' n.e. of the target,
>simplifying identification of the correct field.  An easy way to
>find the target star is to pre-point your telescope at a bright star
>with nearly the same declination west of the target, then turn off
>the clock drive of your telescope at the right time and keep it
>clamped.  For this event, point your telescope at 6.1-mag.
>26 Arietis, at J2000 RA 2h 30.6m, Dec +19 deg. 51', 16 min. 43 sec.
>before the occultation, and then the target star will be only
>0.8'south of where 26 Arietis was when the occultation occurs.  An
>even brighter opportunity exists 29m 12s before, pointing at 5.6-
>mag. theta Arietis, at J2000 RA 2h 18.1m, Dec +19 deg. 54', then the
>target will appear 3.7' south of where theta was at the time of the
>occultation.  You can find the predicted time of the occultation at
>your site (or at one close enough near yours) by checking the site
>list on Derek Breit's web site given above (click on "sites" on the
>line for the event, to the right of the "GoogleMap" item that has
>the interactive detailed maps of the path); the site list also gives
>other circumstances of the event (alt. & az. of the target).  If
>your observatory is not in our list, please send me the coordinates
>and we can add it.  Also on Derek Breit's web site is a long list of
>other pre-pointing possibilities, obtained by clicking on "Stars".
>
>PLANNING COVERAGE OF THE EVENT
>
>      Another way to determine the predicted time at your location is
>to use Occult Watcher (OW), available at
>http://www.hristopavlov.net/OccultWatcher/publish.htm ; we use this
>for planning coverage of the occultation, to select sites for mobile
>stations that complement the coverage by fixed-site observers who
>can declare their intention to observe via OW.  It is also useful
>for letting you know of all updated asteroidal occultations
>predicted to occur within a specified distance of your location.
>Please let us know your intension to observe, either via OW or by
>just sending me an e-mail message.  So far, OW lists 12 stations for
>this event, but 10 of them are plans by Scotty Degenhardt and Roger
>Venable for areas in central Tenn. and S. Carolina that will
>probably be clouded out, so their stations should be ignored for
>now.  Scotty says he'll update his stations Tues. morning when a
>better weather forecast is available and he can decide how far west
>he needs to travel (to western Tenn. or Arkansas) to deploy his
>multiple stations.  The two other stations are in s. California
>where it's likely to be clear, Rick Wasson mobile 4 km n. of the
>predicted central line, and Karen Young at home in Wrightwood 58 km
>s. of center.  The predicted limits are 41 km from center, with the
>predicted limits in case of a 1-sigma path error being 63 km from
>center (but there's a reasonable chance even at 2-sigma, or 86 km,
>from center).  I plan to enter the 6 stations I hope to deploy later
>today, and will distribute a list of the known coverage of this
>event then.  We'd sure like to add you to that list, so please let
>me or OW know.
>
>      I will have limited e-mail access after I leave home to observe
>this event early Tuesday afternoon EST, but expect to have access to
>e-mail up to mid Wed. afternoon at wifi sites in California.
>
>      Note that 3 hours after this event, there will be an
>occultation of a 10.4-mag. star by the asteroid (431) Nephele
>visible from southern California to the Gulf coast of Texas s.w. of
>Houston; its path crosses Hertha's in the Mojave Desert.
>
>      Much information about observing occultations of all types is
>in "Chasing the Shadow:  The IOTA Occultation Observer's Manual"
>available for free download at
>http://www.poyntsource.com/IOTAmanual/Preview.htm .
>_____________________________
>
>David Dunham, 2008 December 8, 2 am EST
>Phones home 301-474-4722; office 240-228-5609; cell 301-526-5590
>