The Graze of Upsilon Geminorum - Apr 16, 2005 UT

4.1 star 10N of 48%+ Moon

This graze was part of Astro 28M Field Astronomy class, and we had 6 stations set up. The data is still trickling in. I have reduced my own videorecording of 6 events. The seeing was OK, the skies were clear, and there was a moderate breeze, blocked somewhat by my RAV4 but still causing some vibration of the image on tape.

A highlight of this graze was the discovery that the star is most likely a previously unknown close binary. Derek Breit and Ed Morana at the Bay Area team site noticed on their videorecordings a faint, ~10th magnitude star after some D's. I found the same on my tape of 6 events. This is a significant interest because the late K giant Upsilon Gem is a standard star used in stellar diameter studies using interferometry. Having a contaminating star so close will not likely be a welcome discovery for astronomers who've used it in this way in the past.

The prediction sheet is here.


Nearby red giant; diameter estimated around 0.3 AU. All timings were gradual. D's and R's have beginning, middle (time of 1/4 maximum light corresponding in diffraction theory to the geometric time of occultation), and end of the fadings and brightenings.

Long: 118 12.22'
Lat: 35 07.07'
Elev 3318 ft (from USGS map). Coordinates from GPS set on WGS84 system.

Ph UT Comments
-- ---------- ----------
bD 4:46:58.06
mD 4:46:58.13
eD 4:46:58.33 gradual fade, no leveling off before invisibility

bR 4:48:02.40
mR 4:48:02.96
eR 4:48:03.23

bD 4:48:04.33
mD 4:48:05.56 ~9.8 mag for ~8 frames
eD 4:48:06.00

bR 4:48:14.13
mR 4:48:14.26
eR 4:48:14.36

bD 4:48:19.00
mD 4:48:19.10 ~9.8 mag for nearly 1 second
eD 4:48:20.10

bR 4:48:26.96
mR 4:48:27.20
eR 4:48:27.30