The Occultation of a 12.5 star by the asteroid van den Bergh

Oct 27, 2021 at 9:30 pm

 

This decent rank event crosses Montara, where we plan to observe it. 1.5 sec max duration. Jerry B in Carson City is also signed on. So with luck we could get 3 chords.

 

 

 

Results:

We got two very different cloud forecasts; this time the optimistic one was the ECMWF, but the GFS prediction seemed better at showing what the satellite was showing during the afternoon. Still, it looked like the cloud (singular!) was hanging just off shore and might be OK for this event which was 31 degrees up in the East. I figured worst case, we could drive over Hwy 92 and set up on the summit. So, we did get a bit of a late start as these on/off decisions changed. In the end, I said "let's do it!" and Kirk was game to carpool with me. We drove up Hwy 1, got to Half Moon Bay and while there were hints of ground fog all along the way, as the damp ground from our recent storm and clear skies made for radiation fog to form right on the ground. At the Hwy 92 intersection, I made the decision to stick with our "Plan A": Kirk on Airport Rd, and me at the Hostel, giving a good spread with Jerry B in Carson City just north of the centerline and us south of it. But as we got to Moss Beach and looking for Kirk's turnoff, we hit fog. I drove further - more fog. I drove up an ascending road on the east, more fog. Now we were getting close and had to immediately find clear skies regardless of where. I drove south on Hwy 1, past Hwy 92, now just wanting to see those clear skies we had on the drive up - they were still there! I looked for a small quiet road of any sort; found one, took the turn, and it was decided we had time to do just one station - I encourged Kirk to set up right next to me, but he declined, as he usually takes more time and we were down to just 1/2 hour before the event. I got set up efficiently, chose Hamal and Altair as my 2-star align and went then to our target, which was in Aries. But the field did not look at all like my charts. I had Kirk double check the coordinates - they were correct, after precessing to the current date as appropriate. I had gotten a "success" on the 2-star align so I didn't question it's validity... I should have. The event came and went w/o us acquiring the target. The field the scope swung to was in Aries, and the target was in the middle of dim stars and not far enough away from where I thought it should be, by naked eye, to arouse suspicioun. But in fact it was many degrees off. When I sent the scope to M45 it went a good 5 degrees away from where it was supposed to.

Learning Moment!: Don't take "Align Success" at face value! If, in the future, you go to your target field and don't recognize the stars, then if time is short, immediately do another 2-star align and chose different stars.

Jerry B had a miss, so most likely the target did shift south and we were well placed.