2022 Occultations by Special Main-Belt Asteroids - Updated 2022 Nov. 19
Another good Antiope occultation Nov. 20/21, cen. Arizona to Iowa
(172376) 2002 YE25 - Another probable binary asteroid discovered by Gault and Nosworthy
These occultations are described and illustrated in this .pdf document. It includes several hot links to external Web pages, but links to internal files, especially the .xml input files used by the Occult program, are given below. _ _ _ _ _ BRIGHT NOVEMBER 20/21 OCCULTATION BY (90) ANTIOPE ACROSS NORTH AMERICA The star to be occulted on Nov. 21 UT by Antiope will be 10.0-mag. PPM 722594 = TYC 6351-01431-1, spectral type G0, 4 degrees west and a little south of Saturn, around 3:13 UT of Nov. 21 UT (which is Sunday evening, Nov. 20, local time), in a path extending from northern Baja California, across Arizona, n. New Mexico, Kansas, Iowa, and becoming too low to observe effectively farther east. (90) Antiope is one of the larger binary asteroids, with roughly equal-size components, so it needs to be handled differently from other events. The ISAM shape model at the time of the occultation is an Earth-plane view. Occult maps that show the Earth as seen from the direction of Antiope are given in the following image files: World View of the path Southwestern USA zoomed in view of the path Central and Eastern USA zoomed in view of the path Here is the S.W. USA Occult map with the ISAM shape model superimposed on it with the right position, scale, and orientation to show how the two components will appear projected on the Earth's surface, created using this Power Point file and the procedures given in this .pdf document. Careful measurement of this map using a digital ruler with the Power Point file allowed determination of the distances of the edges for each component from the predicted central line: km from km for OW and for offsets North Comp. center for Derek Breit's Google Map N. Edge 130 N -130 S. Edge 25 N -25 South Comp. N. Edge 26 S +26 S. Edge 129 S +129 Note that these are just the predicted paths; they have about a 20-km error (1 sigma) and the shape model errors could add to that. Using the information above and Derek Breits Google Map, I have created the static maps below showing the path for the edges of each component over Arizona. On these maps, the dark gray lines mark the edges of the path of the occultation of the target star by the specified component; IGNORE all the other (colored) lines on the map. Path for Antiope northern component across Arizona Path for Antiope southern component across Arizona The errors for this occultation are larger than usual because the target star has a Gaia EDR3 position but no proper motion; for proper motions to calculate the prediction, Steve Preston had to use UCAC5 catalog data based on a comparison of early-epoch ground-based astrometric survey measaurements with Gaia DR1 positions. Some finder charts are below: Naked-eye view (the target is at the left end of the plotted pre-point line) For the other charts below, the target star is centered: Finder scope view, wide Finder scope view Maxi 120mm refractor view 8-in. SCT view, wide This chart shows SAO numbers of the stars on the chart that have them. Note especially 9th-mag. SAO 164216 that is less than 2 arc minutes east, and a little south, of the target star, which is a magnitude fainter. There is also a 13th-mag. star halfway between the two stars, according to Guide8, but this Google Sky zoomed-in view (with celestial north up) shows that star brighter, around mag. 11 or 12. 8-in. SCT view These charts were produced with Guide8 and are valid for the Phoenix, AZ region, where the occultation is predicted to occur at 3:13:06 UT of Nov. 21 UT (= 8:13:06pm MST of Nov. 20 MST), when the target will be 27 deg. above the southwestern horizon (azimuth 220 deg.) and the Sun sltitude will be -35 deg. The charts have zenith up as seen from that area, but the appearance will be similar for other locations in or near the path; however, the times can be several seconds later, and the altitude above the horizon much lower, for locations farther east. For times and circumstances at other locations in or near the path, consult the detailed Occult maps above, and the path information given by clicking on "Detailed Info." below the dark world map on Steve Prestons page for the event. His page also has celestial north-up finder charts of different scales, and zoomable unlabelled Aladin charts are on the Occult Watcher Cloud (OWC) page for the event. Clear skies are forecast for most areas of the path, according to this NWS cloud cover forecast map. Several stations have been declared, as shown in the current Occult Watcher station sort, but we can always use more observers to give better coverage of the occultation. If you might be interested in trying to observe this and you do not already have all of your own occultation observing equipment, contact Ted Blank at tedblank at gmail dot com and meet him at a small star party that will be held Saturday evening at Eagle Mountain Golf Club, off of Shea Blvd. in southwestern Fountain Hills, AZ. Ted can loan you the equipment you need and can help you locate the target with your telescope, if you can bring it. If interested, you should also read George Viscome’s occultation primer. The Occult input file for the Nov. 21st Antiope occultation is here, from Steve Preston's Web site. _ _ _ _ _ CLOUD COVER FORECAST MAPS For some past events, I have posted cloud cover forecast maps, but with time constraints, I will rarely do that in the future. Expedition organizers, mobile observers, and others are encouraged to use the Web sites I use, given below. I find the best and most detailed models are the US GFS and European ECMWF forecasts, available from this Web site. Note that even though it has worldwide coverage, it uses North American Central Time, with Daylight time (CDT = UT - 5h) from 2am of the 2nd Sunday of March to the 1st Sunday of November; at other times, it is Standard time (CST = UT - 6h). Also, at this web site, cloud cover is not given in the default parameters; you need to select "All" parameters and scroll down to expand "Clouds" and select "Cloud cover". I find the GFS forecasts are a little better than the ECMWF ones, and GSF updates every 6h while ECMWF only updates every 12h. For both, you can zoom in by selecting a State or Province, and even a county. I find the easiest site to use, for the USA, is the National Weather Service (NWS) site. The main information you want is "Sky Cover". This site uses North American Eastern Time (EDT = UT - 4h) from 2am of the 2nd Sunday of March to the 1st Sunday of November; at other times, it is Standard time (EST = UT - 5h). The default map is of the "lower 48" US States, but you can select "Go to Region" to select a map showing several States, or one with individual States. Near the bottom of the "Region" menu are options for Alaska, Hawaii, Puerto Rico, and some other US territories. I find it generally too optimistic, but many astronomers prefer the Canadian Weather Forecast for astronomy, also called "Clear Dark Sky" and previously, "Clear Sky Clock". Most use it for individual sites, but it also has maps; I find the most useful to be the Sky Transparency maps that cover virtually all of Canada and the "lower 48" USA. The site uses Universal Time and is updated every 12h. Sometimes, the type of cloud cover matters. Relatively bright stars can often be recorded through high (cirrus) clouds, but not more opaque low or middle clouds. With the GFS and ECMWF forecasts, you can select middle or low clouds, to see if the cloud cover is only high clouds or not. Also, if the relative humidity is high, use of dew shields and other measures, such as finding paved or less vegetated observing sites, may be needed to combat ground fog. It is also useful to look at wind forecasts. _ _ _ _ _ (172376) 2002 YE25 On 2022 June 22, the discovery of another probable binary asteroid by D. Gault and P. Nosworthy, (172376) 2002 YE25, was announced on IOTAoccultations and other lists; more recently, a CBET announcing this was distributed by the Minor Planet Center. It's probably a miniature Antiope-like system with 4-km components separated by at least 15 km. The discovery observation, made on 2022 May 16, involved an 11.0-mag. star and enabled a significant improvement of the orbit of the asteroid. That has been used to compute occultations by it of stars to mag. 14.0 for the rest of 2022, but all of those events are now past, as the asteroid is too close to the Sun to observe. There will be some opportunities during 2023. _ _ _ _ _ OCCULT INPUT .XML FILES FOR 2022 When you open these files with your Web browser, you should get a display that looks like this. The larger files may take a couple of minutes to show this appearance, showing a messed-up display before then. Once the proper view appears, right-click anywhere on the display, then "Save as" to a directory on your computer; the best directory is the \Asteroid\ subdirectory in your Occult\ directory. Worldwide special main-belt events to mag. 14, 511 occultations, not including (4337) Arecibo, (4552) Nabelek, and (33074) 1997 WP21 For the 12 special main-belt asteroid events mapped and tabulated in the main .pdf document North American special main-belt events to mag. 14, 21 occultations Worldwide events (62) for (4337) Arecibo to mag. 16. Worldwide events (149) for (2258) Viipuri to mag. 14. Worldwide events (29) for (33074) 1997 WP21 to mag. 14. Worldwide events (59) for (4552) Nabelek to mag. 14. Worldwide events (59) for (172376) 2002 YE25 to mag. 14. ______ David and Joan Dunham, 2022 November 19 e-mail: dunham@starpower.net cell phone: 301-526-5590