The Occultation of a W=12.3 Star by the Asteroid Shimizu

Fri eve 11:21:14pm June 20, 2025

OWc page

 

This is a good long event of 2.1s duration. The target star is extremely red. The W magnitude from the Hristo Pavlov formula is 12.3, but might look a little brighter or dimmer because it is quite a bit redder than the calibration stars. The near IR J-band magnitude is 8.5 !  But the B magnitude is 15. The V magnitude is 13.0. From the OWc star data, I calculate W=12.3. But the actual magnitude in the Watec is going to be probably a surprise. 

Alt=33, Az=137, in Scutum, 40% of the way from Altair to Antares, no obvious naked eye stars nearby. About 12 degrees to the right of the "tail feathers" of Aquila.

 

     

 

Results:

Richard Nolthenius

We had a very windy night and so I could not set up at Pine Ridge cul-de-sac as planned. I instead drove first to Twin Gates, but it looked like Kirk was already there, so I continued down to Llama Lane and set up there, 27 feet west of the power pole that's about halfway between the two ranches, and just a bit west of the faint curvy 2-track that I have used in the past. There was no wind trouble during the event. But the target was much fainter than I thought it would be, and the seeing was variable and focus was a struggle to find an optimum. But at 32x it was clearly obvious. I set gamma=1 (it was gamma=0.80 for the 2000 SL45 event 80 minutes earlier) because city lights in that direction were still making sky light at 32x a bit of an issue. I saw a clear 2s event on the monitor, which remained attached during the event.

There was a wind gust at event time, unfortunately, but the ref stars only dimmed some, while the target disappeared entirely. The best smoothing length was 2 (!) because the wind gusts caused very short term rattles in light curve. The statistics argue this was real.

magDrop report: percentDrop: 59.4 magDrop: 0.979 +/- 0.725 (0.95 ci)

DNR: 3.02

D time: [06:21:12.3998]
D: 0.6800 containment intervals: {+/- 0.2899} seconds
D: 0.9500 containment intervals: {+/- 0.8691} seconds
D: 0.9973 containment intervals: {+/- 2.2652} seconds

R time: [06:21:14.9598]
R: 0.6800 containment intervals: {+/- 0.2899} seconds
R: 0.9500 containment intervals: {+/- 0.8691} seconds
R: 0.9973 containment intervals: {+/- 2.2652} seconds

Duration (R - D): 2.5600 seconds
Duration: 0.6800 containment intervals: {+/- 0.4671} seconds
Duration: 0.9500 containment intervals: {+/- 1.2728} seconds
Duration: 0.9973 containment intervals: {+/- 2.7912} seconds

     

 

Kirk Bender

I got a recording at 2x of 2000 SK45 from the Glenwood drive parking in Scotts Valley, don't know if I got an event. There was intermittent wind so I collapsed the tripod legs and got close to the car. I went to the trail crossing at UCSC and got a recording at 16x of Shimizu. Looked like a positive. It was barely visible at 8x but there was wind again and not good seeing so I put it at 16x. I also got some test recordings of the Quaoar field with and without the reducer.