Occultation snd Spectacular Graze of 1.6-mag. El Nath, 2025 March 6 pm - New 2025 March 5
by David W. Dunham
______________________________________________________ THE TOTAL OCCULTATION will be visible across only southernmost California and Arizona; most of Mexico, all of Central America, and a large swath of the Pacific Ocean, including the Hawaiian Islands, as shown in the region of visibility map at the top of Rob Robinson's prediction page for the event that also has the predicted Universal Times and circumstances for the dark-side disappearance for 226 cities in Canada (CA), the USA (US), and several other countries, followed by a similar list for the sunlit-side reappearance, and concluded with a list of the coordinates of the cities. ______________________________________________________ SPECTACULAR GRAZING OCCULTATION OF EL NATH, S. CALIF., S. ARIZ., AND N.E. MEX., MAR. 6 PM This great graze on the dark side of a 55% sunlit Moon may be the best in North America this year, so some are planning expeditions to the graze path, shown on pages 173 and 174 of the RASC Observer's Handbook for 2024, and also on pages 1 and 2 of this IOTA grazes paper. Note that the graze will occur around 5h UT of March 7 UT, but that is Thursday evening March 6 local time, 9 pm PST or 10 pm MST. This plain text file gives the Universal Time of central graze, and the circumstances (esp. the altitudes of El Nath and the Sun) at 0.25 degree intervals of longitude along the path from the Pacific to the Gulf coast. After the last (cusp angle) column, we give for many longitudes the city, town, and/or highway crossed by the path there. For most places prefaced with ## or **, Grazprep Google Earth (GE, or.kml) files are provided below, each generated for the average height abovw sea level of the area crossed by the graze path. The NWS cloud cover forecast, as of this afternoon, looks pretty good for the area south and southeast of Tuscon but worse farther west along the path. But it looks like just scattered clouds around Sant Maria and Riverside, Calif. In many areas, the clouds may be thin enough to see the bright star through them. The lunar profile is pretty good along the whole path, such as those computed by Occult for Santa Maria, CA, Santa Clarita, CA, Riverside, CA, and I-19, Arivaca Jctn., AZ, 5-6 occultations of El Nath should occur in the best locations for most of these Occult-generated profiles. These show that the graze will last less than 4 minutes in the interesting parts of the profile for all longitudes, so for your observing time, use the plain text file to find the time of central graze at the longitude For finding sites, it's easier to use the Graz[re[-gemerated .KML files with Google Earth to see the whole lunar profile projected on the ground. IOTA/European Section's Eberhard Riedel has generated several Google Earth (GE) files that will allow observers to select observation sites in narrow bands where the predicted lunar profile shows the maximum number of occultations of the star during the graze can be observed. Thanks to the detailed lunar topographic information derived from NASA's Lunar Reconnaisance Orbiter (LRO), these predictions are quite accurate, much more so than before the early 2000's when we had to rely on Watts charts. Riedel has used his GRAZPREP software to project the lunar profile on the surface of the Earth so that, for any location in the graze zone, you can predict how many occultations of the star will occur. The GE files show, as the northernmost line, white, showing the sea level northern limit for a smooth spherical Moon with its average radius. immediately below (south of) it is a thin blue line that is the smooth-Moon elevation-corrected northern limit. Since this graze occurs in a low part of the Moon, some distance south of these two "smooth Moon" lines is the whole lunar profile, giving on the thin blue lines left and right of the yellow profile, the distance in meters of the line south of the; elevation-corrected northern limit line followed by "8x" or "6x". etc. indicating the # of contacts expected along that line. Divide it by 2 for the # of occultations of the star, so 8x is 4 occultations. Find the lines with highest # of contacts and select it (or them) for finding observing sites. This graze occurs in a low region of the Moon so on the white northern limit line, there will be no occultation, only a close miss. When you first see the yellow profile, it covers up the ground beneath it, but as you zoom in to see more detail, the yellow lines become narrower, allowing you to see the ground features better. From west to east along the path, the GE files are for the following areas (click on the name to get the .KML file): For more about these files, read Eberhard Riedel's message here. The files are listed from west to east, since that's the direction the lunar shadow will move. After the location, the elevation above sea level (h) of the area used for the path calculations is given. w. Santa Maria, Calif., h 85m e. Santa Maria, Calif., h 200m w. Santa Clarita, Calif., h 370m Riverside, Calif., h 315m Palm Desert, Calif., h 200m Growler Norton, AZ, near I-8, h 95m Hwy AZ85 n. of Ajo, h 445m Maish Vaya, AZ, h 770m Hwy AZ86 w. of Tucson, h 890m Kitt Peak, AZ, h 1900m I-19, Arivaca Jctn, AZ, h 940m Hwy AZ82 n. of Patagonia, h 1310m Hwy AZ92, s. of Sierra Vista, h 1500m ________________________________________________________ Maps and lists for 116 of the best lunar grazing occultations across N. America during 2025 (most in the future) are given on this IOTA grazing occultations page. ________________________________________________________ David Dunham, dunham@starpower.net Eberhard Riedel,e_riedel@msn.com