The Occultation of a 12.0 by 10.4 Herculina

Aug 14, 2020 at 11:23:25pm

Preston predictions

 

Northern limit across Watsonville, northern 1-sigma across Santa Cruz. Centerline through Pinnacles. At my actual site off Mar Monte Rd, my nominal odds of a hit in OccultWatcher were 38%.

     

Results:

I ended up setting up off Mar Monte Rd next to the freeway Hwy 1. Got a successful taping. However, I didn't pay close enough attention to how close this 12.18 star was to an 11.08 star and ended up blurring them both together in an attempt to not saturate the pixels, at 8x integration. That means that the actual dip in the total image of 12.0 +11.1 + 10.4 Herculina is not the 0.2 dip of just asteroid+target star but only 0.13. In the graph from LiMovie below, I put a vertical line at the predicted occultation time according to OW. The depth of the event (if it's real) is about from 2950 counts down to 2540, or a dip of 0.16 magnitudes, which is very close to predicted and within my eye-ball error measurements. Now, lets see if any other observations suggest the slight north shift needed. The OW predicted occultation center was 11:23:25pm PDT and I marked it on the chart according to time stamps on the video record. No correction made for the 8x (1/4 sec) integrations used, but that'll be small at this scale. It appears if my event was real and Herculina is circular, that the event was a 3 second early. The duration of my event, as eyeballed, is 14 seconds.

I tried re-doing the video LiMovie photometry with wider aperture circles, in case some of the two stars may have slopped over on some readings. But the final curve looked no better and pretty much identical to the first try, which is shown below.

I'll now await other observations to see if this suggestive dip is real and timings should be estimated. As it, stand alone, I wouldn't report it.

The LiMovie graph, with no comparison or trackng star used. The star images were significantly defocused, so that the target and the neighboring 11.1 star were both included. That means the predicted dip is not 0.2 magnitudes but 0.16 magnitude. The observed dip, if real, is 0.13 magnitude, eyeballed in in Photoshop

Without correcting for time stamp offsets, but the duration of the dip I drew in is 14 seconds.

 

It looks like only Jerry B got data. Not good enough to make a judgment on a shift. Derek didn't get observations. Mine alone don't make the S/N cutoff for confident judgement of an occultation here, so I'm making no report.