Two Recent Aldebaran Grazes (and one of gamma Librae) David Dunham IOTA meeting, Carson City, NV, 2017 Sept. 9 2016 July 29th am Aldebaran; graze in TX and OK Feb. 18th am gamma Librae graze near Kutztown, PA Mar. 4th pm Aldebaran occ’n; graze in NY and ON

View of Moon for the Aldebaran Graze, July 29, 2016 _ Aldebaran This is the view of the 23% sunlit waning crescent Moon as seen from Oklahoma, but the view will be virtually the same for other locations along the graze path across North America. The orange star will appear to approach the Moon from the sunlit side, passing very close to the northern cusp, where binoculars will probably be needed to see the star a few minutes before the graze. The star will become easier to see, even with the naked eye (where strong twilight or daylight doesn’t interfere), as it moves onto the dark side during the graze. The dark side of the Moon is faintly illuminated by “Earthshine”, and the darker “maria” (lava-filled “seas”) can be seen with binoculars.

2017 July 29 Aldebaran path across USA Northern-limit graze

Carey, TX (nw of Childress)

Carey, TX

US 177 Sites Beautiful site only 19 miles south of Stillwater. Graze occurred from 10:06.0 to 10:09.2 UT. Moon alt. 28°, az. 90°, Sun -16° Light traffic then, wide shoulders and fields extending to east Only one house & couple of businesses in the zone Art Lucas has talked to the residents, they were ok with our presence.

Spectacular Grazing Occultation of 3. 9-mag Spectacular Grazing Occultation of 3.9-mag. gamma Librae by the last quarter Moon Sat. 3:29 am, Feb. 18, graze 9 deg. from south cusp on the dark side; altitude 25° Grazes this bright with profile this good are rare, this close only about once every 2-3 years Expedition south of Kutztown, PA Clouds threatened during the evening, but by midnight, they had largely dissipated. Past observations showed that the star may be a close double, but our observations of this graze only showed effects of the star’s angular diameter & diffraction, with no step events that would have been indicative of stellar duplicity.

This grazing occultation is special not only because the star is so bright, but also because the lunar profile (shown below) lines up to produce an unusually large number of disappearances and reappearances in a narrow zone. The gray bars on the left side indi- cate the # of events at different distances from the predicted southern limit line. The vertical Scale is ex-aggerated by factor of about 20 relative to the hori-zontal scale This profile is a zoomed-in view of the graze zone of the Moon  Narrow Zone  Gradual and partial events, like those for Aldebaran grazes, will occur due to Fresnel diffraction of the star’s light at the Moon’s edge; to see what it may be like, look at some of the YouTube videos at http://www.asteroidoccultation.com/observations/AldebaranGraze_29July2016/ Time relative to time of central graze in minutes The LRO laser altimeter data allows us to predict these narrow zones very accurately now.

Spectacular Grazing Occultation of 3. 9-mag Spectacular Grazing Occultation of 3.9-mag. gamma Librae by the last quarter Moon Sat. 3:29 am, Feb. 18, graze 9 deg. from south cusp on the dark side; altitude 25° 2 1 5 4 3 6 We observed from 6 sites (4 remote, 2 attended) on and near the western parking lot of the St. Mary’s Catholic Church complex south of Kutztown, Pennsylvania

Spectacular Grazing Occultation of 3. 9-mag Spectacular Grazing Occultation of 3.9-mag. gamma Librae by the last quarter Moon Sat. 3:29 am, Feb. 18, graze 9 deg. from south cusp on the dark side; altitude 25° Lightcurve of the occultation obtained at Joan’s station 3 using a 12cm Orion short-tube refractor on an iOptron mount. David used another 12cm short-tube refractor at station 5, equatorially mounted with manual slow motion controls.

Spectacular Grazing Occultation of 3. 9-mag Spectacular Grazing Occultation of 3.9-mag. gamma Librae by the last quarter Moon Sat. 3:29 am, Feb. 18, graze 9 deg. from south cusp on the dark side; altitude 25° The 4 remote stations used 8cm Orion short-tube refractors on stationary pre- pointed “alt.-alt.” paver mounts like the ones shown above. On the right, Joan is using one to practice observing the Sun for the March 2016 Indonesian total solar eclipse.

Reduction Profile of the timings made by the Dunhams near Kutztown of the Grazing Occultation of gamma Librae by the last quarter Moon Saturday 3:29 am EST, Feb. 18, 2017 The dots mark the disappearances and reappearances recorded at each station. The ordinate is distance in arc seconds below the Moon’s mean limb (this is a low area of the Moon, in the South Pole Aitken Basin that is mainly on the back side of the Moon) at the Moon’s average distance, while the absicca is position angle measured around the Moon’s disk from the north pole spin axis projection. The curve is the lunar profile as calculated from LRO laser ranging data. There is about a 30 times exaggeration of the vertical scale relative to the horizontal scale.

View of Moon for the Aldebaran Graze, March 4, 2017 The “x” marks where Aldebaran will disappear, at 11:05 pm, in central Maryland. It will be a naked-eye event (tell your friends), although binoculars will give a better view. A telescope will be needed to see the bright-side reappear- ance at 11:39 pm. The Moon will be 19° above the western horizon at the disappear- ance and 13° up at the reappearance. This is the best occultation (and graze) of the current series of Aldebaran events for the n.e. USA, and conveniently on a Saturday evening. The next series will start in about 15 years. X Graze | | This is the view of the 46% sunlit waxing first-quarter Moon as seen from Michigan, but the view will be similar for other locations along the graze path Across North America. However, west http://occultations.org/aldebaran/2017march/ of Montana, the graze will be mainly on the sunlit side of the northern cusp. The orange star will appear to approach the Moon from the dark side, passing very close to the northern cusp. The star might be seen even with the naked eye before the graze, and in the East, during at least the first part of it, but binoculars will give a better view, and a small telescope will be needed to see the events that occur among sunlit features. The dark side of the Moon is faintly illuminated by “Earthshine” with the “maria” (lava-filled “seas”) appearing darker.

Spectacular Grazing Occultation of Aldebaran by the first quarter Moon 2017 March 4, graze 4 deg. from the north cusp on the dark side

GFS weather forecast for the occultation and graze

Spectacular Grazing Occultation of Aldebaran by the first quarter Moon 2017 March 4, graze 4 deg. from the north cusp on the dark side Saugerties  Joan and I observed from the Hudson Valley, near the town of Saugerties about 100 miles north of New York City. It was clear and cold, temperature 12° F.

Lunar Profiles for the Aldebaran Graze, March 4, 2017 White Rock, BC -3 min. +3 min. North Cusp Sunlit Route 1, ND -2 min. +2 min. North  Cusp -2 min. +2 min. Oscoda, MI -2 min. +2 min. Narragansett, RI A caption describing the profiles is on the next slide. At Saugerties, NY, the profile was similar to the one for Narragansett.

Lunar Profiles for the Aldebaran Graze, March 4, 2017 Caption (for the figure on the previous slide) The predicted lunar profile is shown for four locations along the graze path, based on NASA Lunar Reconnaissance Orbiter laser altimeter measurements as plotted with IOTA’s Occult 4 program. The smooth curve (dotted on the Moon’s dark side) shows the Moon’s average radius. A horizontal line shows the path of the star for an observer at the predicted northern limit, with tick marks at 1-min. intervals relative to central graze. Other observers near the northern limit will see the star follow a similar horizontal path from left to right, but displaced north or south of the plotted horizontal line, depending on the observer’s distance from the predicted northern limit shown with the vertical scale in kilometers (on both sides). The gray bars on the left side shows the number of occultations of the star by different lunar features that is predicted for each observer, with the distance from the left edge proportional to the number of occultations. Observers will want to locate their observing sites at distances where the most occultations are predicted. In flat areas of the profile, more occultations than indicated are likely. The top profile is for White Rock, BC, directly south of Vancouver. The graze zone is only a mile north of the US border and small telescopes are needed since the graze will occur on the sunlit limb. Near North Dakota Route 1, most of the graze will be on the Moon’s dark side, although the high mountains just after central graze will likely be sunlit. Along the path, the profile lines up best, for the most occultations of the star, at Oscoda, MI, on the west shore of Lake Huron, but the show will be nearly as good in the path across Michigan, Ontario, and into central New York. The last profile is for Narragansett, RI, the easternmost land in the graze zone; the Moon will be 13° above the western horizon there.

Spectacular Grazing Occultation of Aldebaran by the first quarter Moon Sat. 11:19 pm, Mar. 4/5, graze 4 deg. from north cusp on the dark side; altitude 15° 1 2 6 We obtained permission from David Tromp to use the land, currently unoccupied. We planned to run 8 video stations, but only remote stations 1 & 2 worked. Stations 3 & 4 failed due to the cold conditions, & 5 was left unoccupied due to a bright security light in the Moon’s direction. My scope at 6 failed in the cold, so I used the finder & a camcorder to make visual timings. Ran out of time so stations 7 and 8 were not used.

Spectacular Grazing Occultation of Aldebaran by the first quarter Moon Sat. 11:19 pm, Mar. 4/5, graze 4 deg. from north cusp on the dark side; altitude 15° Lightcurve of the occultation obtained at remote station 2 using an 8cm Orion short-tube refractor on a paver mount. Only the tops of the highest mountains briefly occulted the orange giant star. Stations 1 and 2 were 40m apart, close to the projected (44m) diameter of Aldebaran. At station 1, for the last occultation, the star never completely disappeared, being about 25% of its unocculted brightness at minimum.

Reduction Profile of the timings made by the Dunhams near Saugerties of the Grazing Occultation of Aldebaran by the first quarter Moon Saturday 11:19 pm EST, March 4, 2017 The dots mark the disappearances and reappearances recorded at each station. The ordinate is distance in arc seconds below the Moon’s mean limb at the Moon’s average distance, while the absicca is position angle measured around the Moon’s disk from the north pole spin axis projection. The curve is the lunar profile as calculated from LRO laser ranging data. There is about a 30 times exaggeration of the vertical scale relative to the horizontal scale. The star’s motion on this plot was from right to left.

Spectacular Grazing Occultation of Aldebaran by the first quarter Moon Across e. Michigan, s. Ontario, and w. New York

Ten observers braved bitter conditions to set up six video stations across the graze zone. https://vimeo.com/209854850

Spectacular Grazing Occultation of Aldebaran by the first quarter Moon Across e. Michigan, s. Ontario, and w. New York