2024 August 11 Occultation of 13.4-mag. star by (617) Patroclus/Menoetius - Help complete shape models for the Lucy flyby - New 2024 July 29
The Aug. 11th Patroclus system orientation is the last one previously unmapped and is also by far the best occultation in N. America before the Lucy flyby
Dozens of observers will soon converge in Lamar, Colo. or Raton, N. Mex. in what may be SwRI's last large funded campaign for a Lucy target event
As explained on pages 2 and 3 of our Trojan occultations document, IOTA's and Occult Watcher Cloud's (OWC's) predictions for this occultation, and for all occultations by this binary system, can be in error by up to two Patroclus path widths. Only the predictions of SwRI (the Southwest Research Institute), based on proprietary observations of past occultations by the pair obtained from expeditions that they funded during the last few years, are accurate enough for locating observers in the paths for the occultations by these important objects. Pages 8-10 of the document ahows the meagre possibilities in North America for occultations by this interesting system from after this year to the Lucy flyby in March 2033, underscoring the value of this Aug. 11th occultation. They show a couple of good opportunities in Europe and note a couple of others worldwide, and give a link to an Occult4 input file that allows you to see the multi-year possibilities in your area. See IOTA's Trojan occultations .pdf document and the updated SwRI map for this event, and its description, and about the campaign being organized for it. My recent message about this important event is in this .pdf, and SwRI's Marc Buie gives his strategy for the event, and the procedures and equipment needed to observe the event, in this .pdf nessage. Important updated information is given by Marc in these messages from the Lucyoccs Slack channel for this event. The goal is 1-km accuracy for the observed points on the sky-plane. This can be achieved with timings accurate to 0.2s or better for this slow event. Our tests showed that this can be achieved with a video recording with an IOTA-VTI and a Watec 910HX camera on a 20cm (8 in.) SCT; a good image of the target star was recorded at 8x integration (= 0.16s with our PAL camera), and when conditions were best (we had some thin cloud the night of our tests in Maryland), 4x integration (0.08s) also showed the star. _ _ _ The star, Gaia G-mag. 13.4mag UCAC4 385-001287, is at J2000 RA 01h 08m 10.1s, Dec -13 06' 28", which is 7.7 deg. northeast of 2.0-mag. Diphda (= beta Ceti; it could be used as a naked-eye alignment star) and 2.9 deg. south of 3.4-mag. eta Ceti (Deneb Algenubi = SAO 147632 = HIP 5364) and only 9' north of 8.9-mag. SAO 147628 = HIP 5331. That SAO star forms an easily-recognizable wide (1.8') double with 9.9-mag. PPM 709849 (in neither the SAO nor HIP catalogs). The Guide9 UCAC3-based mag. of the target is 14.1, while AAVSO's APASS gives V= 14.1, B 15.6, and SR 13.5. The star is red, as shown by the B-V, and we found that its appearance seemed to be what one would expect of a 13.4-mag. star, in agreement with the Gaia G magnitude, when we recorded the star on July 22nd. Of course, don't confuse this with the G* magnitude (8.4), a "fake" magnitude to gauge an event's observability by factoring in the event's very slow motion and relatively long duration (for asteroidal occultations); you won't "see" anything like that! The charts below were created with Guide9 in three groups, the first naked eye views and for finder scopes, for both of the other two groups; the second with direct views as we'll have with the 8-in. SCT and Watec video camera that we'll be using, and the third group with an 11-in. SCT with hyperstar and QHY 174M GPS camera at prime focus, similar to most, if not all, of the SwRI systems. For all of our Guide charts, zenith is up, but since the star at the event time is close to the meridian, the views with celestial north up are virually the same. The charts were created for a location in the SwRI Patroclus central line near Carrizozo, NM, but the views will be similar for other locations throughout the Patroclus path, and also good enough to us by observers in the Menoetius path, where the star and Sun altitudes will be just a few degrees different. _ _ _ NAKED EYE AND FINDER SCOPE Naked Eye View, Zenith up to mag. 5.5 Besides the target star (centered, as it is on all but one of the other charts noted below), the "prepoint line of declination" is also shown; this is the trace in the sky of the altitude and azimuth of the occultation as a function of time. Consequently, the time (UT) is marked at about half-hour intervals along the line. Most of us in the Patroclus path will be in the Mountain Daylight Time Zone (subtract 6 hours from UT to get MDT) while those in the Menoetius path, mostly in Texas, will likely be in the Central Daylight Time Zone (subtract 5h from UT to get CDT). Fortunately, the altitude of our occultation will be relatively high, but if at your site, there is a tall tree or other high obstruction, you may want to know if the target star will be blocked by it rather than by our asteroid targets. For example, if at 8:50 UT (= 2:50 am MDT), you can see Saturn from your intended site with at least 7 deg. clearance, you know you can point your telescope with a clear view of the target at event time there. The whole pre-point line from dusk to the event is shown on this wide-field Level 2 Guide chart, in case you want to check for obstructions before 8:00 UT. Mighty Mini/Finder Scope View, Zenith up to mag. 9.0 The rectangle is about 2 deg. high and 3 deg. wide, the FOV of "mighty mini" video finder scopes; typical visual finder scopes have a FOV about 5 deg. in diameter, so a little larger than the rectangle and completely enclosing it. Saturn is shown in the naked-eye chart with link at the top of the previous paragraph, in n.e. Aquarius, above and to the right of the target. For quick aligning a Go-To scope, you might do a solar-system align with Saturn, then go to Diphda, the 1.4-mag. star 8 deg. southwest of the target, and synch (PAE) to that star; then you can go to either the target star coordinates or to 8.9-mag. SAO 147628 = HIP 5331, the brighter of the double star south of the target and from which the target should be in the same FOV. Alternatively, with a 2-star alignment, start with any 1st-mag. star for the first star, and Diphda for the second one, which should give you a good alignment in the target star area, from which the plate-solving procedure should quickly get you on target. _ _ _ 8-INCH SCT VIDEO SYSTEM WITH 0.5 FOCAL REDUCER, DIRECT VIEWS 8in SCT view, zenith up to mag. 14.2 8in SCT view, zenith up, most detailed to mag. 15.0 _ _ _ 11-INCH SCT, HYPERSTAR, AND QHY 174M GPS CAMERA, REVERSED VIEWS These are for the SwRI CPC11 systems, but the FOV shown by the rectangle needs to be checked with an actual image of the field, which SwRI will soon provide with the guide they will soon make available on the lucyoccs slack channel for the event. Since these systems have only one optical reflection, they are mirror image views, reversed from direct views in the east-west direction. SwRI CPC11 view, zenith up to mag. 14.2 SwRI CPC11 view, zenith up, most detailed to mag. 15.0 The Occult Watcher Cloud (OWC) link for this occultation is https://cloud.occultwatcher.net/event/1318-617-16353-647185-U001287 which I give primarily so that you can get the zoomable Aladin photographic star charts at the top of the page (get them by clicking on the degrees numbers under "Star Chart" at the top middle of the page, but YOU MUST NOT USE OWC FOR LOCATING YOUR OBSERVING SITE, since the OWC paths for Patroclus and Menoetius (the above link is only for Patroclus) are not accurate, as explained at the top of this page. Only the SwRI Google Map should be used for observing site selection. The OWC map does have one use, since if you click on any location on it, you will get the altitudes of the target star and of the Sun at the occultation time, at that location. But do not use the U.T. time given there; that is best done by interpolation of the time points on the SwRI map. The very deep Aladin charts from OW cloud are below, showing only part of the area of the most zoomed-in (Level 8) Guide charts given above. They do show the distinctive double star, labelled A and B like on the Guide charts, but star C on the Guide charts is not on these Aladin charts. Aladin direct view, north up Aladin reversed view, north up (for single-reflection systems like the SwRI CPC11's) David and Joan Dunham, 2024 July 29. e-mail: dunham@starpower.net cell phone: 301-526-5590