The Occultation of a W=13.7 Star by Asteroid 1999 CD138

Thur morn July 23, 2026 at 12:29:09am

OWc page

 

This event is faint, but long enough to be detectable I believe. The path is through Santa Cruz. Kirk and I are comfortably inside the path. I will try from home if I can. Otherwise I might drive to West Cliff if I can't get a workable horizon from home

Alt=22, Az=193 in Sagittarius, just 1 deg above left of Delta Sag, where the spout meats the teapot, top boundary. Also 1 deg above bright globular cluster NGC 6624

     

 

Results:

I drove to West Cliff; the first parking inlet east of the entrance to Natural Bridges, several curves away actually. Kirk got fogged out at the last minute. Karl was not in the path. Just me...

Richard Nolthenius

     

 

I got on target efficiently, had to go to 32x to see the star well, which was worse than I hoped, but at 16x I just couldn't see it often enough to make it usable. 32x means I'll get only 1 or 1.5 dots inside the occultation, which is asking a lot. Fog stayed away until after the event. I had to dial the 'brightness' way down, and the contrast way up. The star was visible on every integration on the computer, but got very faint on some. It looked to be gone entirely at the predicted moment, so I may have a single point occultation. Not reduced yet.

PyOTE says for the 2.4px mask I used, that the event of duration 0.8s was not detectable. The sharp drop at the predicted time is suggestive of a real event, however, so I will have to file it as "unsure". Kirk was clouded out after set up. Karl did not try it.