Summary of the Occultation of SAO 108610 by 25 Phocaea

October 3, 2006

00:52:08.90 UT  (first event)

October 2, 2006 at 8:52:08.90 EDT

Latitude:  43 d   00 m   24.0 s   North
Longitude:  77 d   07 m   06.0 s   West
Altitude:  158 m

+ 51 km from the predicted path (west)

Newark, New York
10" LX200GPS at f/6.3 using PC164C gain modified video camera
Recorded by Brad Timerson

Predicted path of occultation from Steve Preston
Approximate observatory location shown just below Lake Ontario to the west of the predicted path.

Here is a low-resolution video clip of the event from YouTube
  The video starts a few seconds before the WWV time signal at 00:52:00 UT, which can just be heard.
First disappearance occurs nearly 9 seconds after that time signal.
Watch as the star/asteroid combination dim to the magnitude of the asteroid only.
Then the star reappears, disappears, and reappears in rapid succession.
This looks like a GRAZING occultation by an asteroid!



Graph produced from LiMovie analysis of the Occultation
LiMovie Analysis Graph

Star first disappears at 00:52:08.90 UT

Stays hidden for 102 video frames - 3.40 seconds
Reappears for 14 frames - 0.47 seconds
Disappears for 9 frames - 0.30 seconds
Reappears for good at 00:52:13.07 UT
Profile resulting from analysis in OCCULT software

The colored lines show where the star never disappeared (lines top to bottom)
and where the star was hidden by the asteroid for varying durations at various observing sites.
Notice chords 16 and 17, mine.  You can compare them directly with the graph
above to see how the star was blocked by the asteroid, reappeared for a brief time,
and was then blocked again before the event finally ended.
Below is one person's (Richard Nugent) idea of how the asteroid
might have looked if we could have actually seen it.
Notice the gap in the upper right side.
In a presentation to an astronomy group a few weeks after the event,
one of the other observers, Guy Nason from Toronto, Canada, gave
the gap a name. It is now known as "Timerson Gulch" in the literature.