Southern California Occultations - Updated 2020 July 11

This is a new Web page, to provide information about lunar and asteroidal 
occultations specifically for southern California; it extends to Calif. 
and supplements more extensive coverage of occultations given for areas 
farther east, for Arizona, as given here.
 
The next asteroidal occultation will pass to the north, over central and 
northern California at 9:28 pm PDT Monday evening, July 13, when the 200-km 
asteroid (532) Herculina will occult a 10.2-mag. 
star in Sagittarius. Finder charts and details about it are here. Observations 
of an occultation of a 6th-mag. star by Herculina in 1978 indicated that the asteroid 
may have a large satellite a few hundred km away. So even across southern 
California, observers have a chance to see an occultation that could confirm 
the possible 1978 satellite.
 
I recommend that you download the lists of asteroidal and total lunar occultation predictions 
for 2020 mentioned below; you can then use a word editor, such as Notepad (these are 
plain text files), to remove lines for past events. The files need to be displayed with a fixed
font like Courier New for the columns to line up properly. Also, a small font size and landscape
mode should be used to prevent wrapping of the long lines.
 
A list of asteroidal and planetary occultations visible from or within 200 km of the 
Orange County Astronomers Observatory at Anza during the rest of 2020 is here, 
and an explanation of them is here. These are from the IOTA main list 
(Steve Preston's site), but these predictions are updated and new events from other sources are 
added during the year, so for events occurring during the next month or two, it's better to use 
the free IOTA software Occult Watcher. A list of the Occult Watcher events within 
200 km of Anza is here, including local circumstances (at the bottom) for an occultation of 
12.1-mag. UCAC4 414-141132 that will occur Tue. morning, July 21 at 
1:20.4 am PDT (= UT 8:20.4). The path is shown in this map, where the green line is 
the predicted central line, the blue lines are the predicted limits, the thick red lines are 
the limits in case of a very possible 1-sigma shift of the path north or south, and the thin 
red line is the s. limit in case of an unlikely 3-sigma shift of the path to the south. Two 
telescope symbols show the planned locations for Greg Lyzenga 
who currently plan to try the event from Altadena, while other thin black lines show the coverage 
by observers farther east, in Arizona. The bottom of the larger telescope symbol marks the 
Orange County Astronomers observatory in Anza, within the path north of the southern limit, 
with a high 85% chance for an occultation.
 
Different methods of timing occultations are summarized here. Information about using an accurate 
smart phone flash timing app is here.
More information about observing occultations is on IOTA's main Web site, in the observing 
section here.
 
A list of TOTAL LUNAR OCCULTATIONS visible from Anza through Sept. 30 is here 
while a list of only events brighter than 7th mag. for the rest of 2020 is here; there are 
usually at least a few visible each night that the Moon is above the horizon. Note that the 
times in this list are Universal Time; subtract 7h from them for PDT and 8h for PST (during 
most of November and December). A rule of thumb, for events between 0h and 7h UT, just add 
the UT hour to 5pm and subtract a day, for PDT; for PST, add instead to 4pm. Also in the list 
are given lines with brief information about any lunar grazing occultations visible within 
a few km of Anza. Information about grazing occultations across southern California will be 
added later. A description of the lunar occultation predictions, including towards the end, 
how to time and report observations of them, is here.
 
This .pdf document prepared by George Viscome is a good introductory 
guide for those wanting to get started with observing occultations, 
especially with the latest video equipment and techniques; it's more 
up-to-date than the other links below. As noted in it, the IOTA-VTI's are 
available again, so we recommend them as sold through the IOTA store here.
IOTA's main Web site has comprehensive information and links to 
all of IOTA's resources worldwide. 
 
This Web page is hosted on a server at the Johns Hopkins University's
Applied Physics Laboratory (APL) in Laurel, Maryland. APL sponsors a 
STEM mentoring program with local high school students for various 
projects in a program called ASPIRE. Alex Knox is one of those students; 
she worked with IOTA member Steve Conard to develop an automated 
remote station system that she presented on May 13th. Her Powerpoint
presentation is here.
_____________________________
 
David Dunham, e-mail: dunham@starpower.net