Fortunate Fortuna on Friday the 13th - New 2007 April 13, 21h UT
At least 9 chords well-spaced across the large asteroid were timed
The path shifted at least 1.8-sigma south of the prediction and the event was 4s early
I managed to run 3 stations for last night's (19) Fortuna occultation with a total road separation of 80 miles, my largest spread. Two of the stations recorded the occultation, but the northernmost one apparently had a miss (the star is faint on that record due to coma, that is, smeared out image due to some optical misalignment; it looks like there was no occultation, but maybe a Limovie analysis might find a short one). This implies at least a 1.8-sigma south shift of the path. The observations that I know of so far are summarized below. Occultation of TYC 0272-00940-1 by 19 Fortuna on 2007 Apr 13 Distance from center of occultation path - in km Proba- Location km bility 148 50% *** Predicted Northern limit *** 146 52% Ashland VA Joe Sedlak - no occultation 79 97% Carson VA D. Dunham remote - no occultation (probably) 31 100% Skippers VA D. Dunham remote - 14s occultation 20 100% Regina SK Vance Petriew - 17s occultation 3 100% DODGEVILLE WI OESPER~DAVID - 17.47s occultation -1 100% Northfield MN Messner~Steve - 17.71s occultation -40 100% Dortches NC D. Dunham mobile - long event video recorded -68 98% Alberta visual "about 12s" but must be longer -83 96% Alberta Alister Ling - 21.54s occultation -120 78% Alberta Mike Hoskinson - 19.8s occultation -148 50% *** Predicted Southern limit *** -186 16% ** Pred. Southern limit plus 1-Sigma ** -191 12% Dark Sky Obs. Boone NC D. Caton - 11s occultation -223 2% ** Pred. Southern limit plus 2-Sigma ** The good spread of observers across the path, including relatively short events near both limits, ensures that we'll obtain a good profile for this occultation, lucky in spite of the "Friday the 13th" large path shift. From my recording at Skippers, VA, the actual occultation occurred only 4s earlier than the prediction. John Goss tried to observe visually at Fincastle, VA at -6 km, but it was very windy and the seeing was so bad that he could not tell if an occultation dimming occurred there or not (it must have, as you can see above). Bob Anderson couldn't observe at Greenbank, WV due to sleet, but at +90 km, he would have had no occultation. For reporting observations, even if the star is monitored and no occultation is seen, you should use the new report forms that you can get here and click on "Templates for Report Forms". Completed reports should be sent to reports@asteroidoccultation.com and copied to Jan Manek at jan.manek@worldonline.cz . The above Web site also contains the results of all North American asteroidal occultations observed during the last few months, including profiles of the asteroids determined from the observations, maps showing observer locations, and other details. Further details of last night's Fortuna occultation will be posted there as observers send results to the above e-mail address. David Dunham _____________________________________________________________________ Prediction/pre-event information for the Occultation by (19) Fortuna Thurs. night/Fri. am, April 12/13 Please help us measure the size and shape of the large asteroid (19) Fortuna by observing its occultation of an 11.0-mag. star near beta Virginis Thursday night/early Friday morning, April 12/13. Let me know your plans to try to observe this event so that mobile observers don't duplicate your observation. The target star should be easy to find since it's only 6' east-southeast of 7.3-mag. SAO 118981 (in the same high-power eyepiece or video field), which is only 2.5 deg. west-southwest of beta Virginis (within the same finder scope field of view). The first (41h prognosis) Astro Meteo forecast shows clear skies over the path across most of Virginia and n. & e. North Carolina, where the occultation will occur at 1:05 am EDT (5:05 UT); clouds are expected in s.w. VA and the central Shenandoah Valley. The 296-km-wide path extends northwestward, passing over southern Wisconsin (Milwaukee near n. limit) and southern Minnesota (Mineapolis) at 5:07 UT, North Dakota at 5:08 UT, Regina and Sasktatoon, Sask. at 5:08, and Edmonton at 5:10 UT; clear to partly cloudy skies are expected in those areas. Unfortunately, rather heavy cloud cover is forecast in the path over most of the Midwest, including W. Va., Ohio, n.e. Kentucky, Indiana, & n. Illinois. The target star, TYC 0272-00940-1, is at J2000 RA 11h 40m 49.5s, Dec +0 deg. 55' 26". 7th-mag. SAO 118981 is at J2000 RA 11h 40m 24.1s, Dec +0deg 57' 07". A N. American path map and finder charts of different scales are on Steve Preston's Web site. I have put Steve Preston's map and finder charts, with labels for SAO 118981, in this Power Point file. If an occultation occurs (and there is greater than 90% chance of that in most of the predicted path), there will be a 0.9-mag. drop that should be easily noticed by visual observers lasting 22 seconds for a central event. Very detailed maps for this and all other events listed below are on Derek Breit's interactive Web page that links to the very detailed maps and satellite imagery of maps.google.com with overlays of the occultation paths. Also on Breit's Web site are station lists giving local circumstances, for many observer stations. It gives the predicted time of the event, distance from the updated central line, probability that an occultation will occur there, and altitudes of the star and the Sun. If your station is not in that list, please let me and Derek, breit_ideas@hotmail.com , know so that you can be added to future lists. Also included there now are lists of stars with offset times and declination differences for pre-pointing telescopes for these events. For those observing near I-95 in Virginia and N. Carolina, I have calculated the U.T. and EDT times for the pre-point stars in this table. Again, please let me know your plans so that I (and any other mobile observers) can avoid duplicating your observation. You can see the distance of your station from the predicted central line in the sites list on Derek Breit's Web site specified above. I plan to run 3 stations for this occultation, near Carson, VA at +79 km, near Skippers, VA at +31 km, and at -61 km near I-95 exit 127 in NC, but I can change these plans to avoid yours. Note that Steve Messner said he'd try it near the central line (+1 km) from his observatory in s. Minnesota. I may distribute a last message by e- mail as late as 10 am EDT April 12 (14h UT), and will be reachable by e-mail at my office up to about 2 pm EDT (18h UT), by which time I'll put any last information on my Web site here (if this is unchanged, assume I'll proceed with my plans described above). After 2 pm, I'll be reachable by cell phone, and less frequently by my office e-mail via my Blackberry - see the bottom of this page. David Dunham, 2007 April 13, 5 pm EDT Phones home 301-474-4722; office 240-228-5609; cell 301-526-5590 e-mail david.dunham@jhuapl.edu home e-mail: dunham@starpower.net .