Friday, 9 Dec 2016
It’s a cold day with a few puffy clouds, but the cloud is forecast to be gone by evening and the sky’s supposed to be transparent. There’s a ¾ waxing moon, wind and the temperature’s at about freezing. Dome opened & turned on before dinner. Out by 17:30 dressed in Arctic type clothing that includes an electrically heated liner. All but the first observation will be in the northern hemisphere and that’s a good thing as the transparency isn’t as good as forecast and the moon is causing a “white-out”.
2016 SD is a 19.2 mag Apollo low in the SW. Started imaging at 17:39 but realized that I’d forgotten to activate The Sky 6 that allows synchronizing coordinates to images. Had to redo the AO calibration and by that time the asteroid was gone.
2016 XK18 is a tough 95-meter sized 19.5 magnitude Apollo discovered 2 days ago. It’s passing within 4 million miles of Earth and relative motion is fast. Imaged from 18:08 – 19:08 at 1 min, 2X2, -15C, 3 Hz. Can’t see it even stacked 10 deep in 5 stacks.
The moon is wiping out the entire southern sky with glow. At 29°F one would think that the air would be dry and clear, but I can’t see diddly squat visually. Rick called to confirm that he and Lisa were coming over and we cancelled based upon the sucky visibility.
2006 UM is 16.6 mag and should be easy. But my planning was faulty. It’s right next to a 4th mag star and unworkable.
2016 XC18 is a 275-meter sized potentially hazardous Apollo now a dim 19.4 magnitude and 15 million miles distant. Discovered just 3 days ago, uncertainty level is 8 on a scale of 0 – 9. Motion is 2.8’/hr. The star field is very crowded. Imaged from 19:23 – 19:56 hours at 2 min, 2X2, -15C, 2 Hz. The sky’s still hazy and what would normally require a 3 or 4 minute exposure is taking 8 minutes and it’s still marginal. Frames 1-4, 5-8 & 9-12 show ∆RA = -0.2’ & ∆Dec = -0.1’ S/N and FWHM are 5.9/4.0”, 4.6/4.2” and 6.9/5.5” respectively. Weak but OK.
420591 is a 869-meter sized Apollo now 18.3 mag and 0.26 AU out. Discovered 4 years back there must be perturbations as uncertainty level is still 2. Motion is 2.5’/hr. Imaged from 20:06 – 20:16 at 2 min, 2X2, -15C, 2 Hz. Oh my! The temperature’s down to 27°F and the transparency has suddenly improved enormously. Moon glow’s gone way down and many stars visible naked eye. Frames 1, 2 & 3 show ∆RA = -0.1 & ∆Dec = +0.1’ S/N around 10 and FWHM has tightened up considerably to around 3.5”
326683 is a 1.4 km sized Amor now a very bright 14.9 magnitude and 0.15 AU distant. Uncertainty level is 1 and motion is 5.6’/hr. The sky’s cleared up nicely. Imaged from 20:24 – 20:41 at 1 min, 2X2, -15C, 4 Hz. Frames 1, 6 & 11 show ∆RA = -0.2 & ∆Dec = -0.3 At this brightness S/N is huge at around 56:1 while FWHM is tight at 4.1” Photometry confirms 14.8 magnitude.
85906 is a 6-km sized main belt asteroid in the 326683 FOV. It’s 17.8 mag and 1.3 AU distant, moving slowly at 40”/hr. RMS residual is 0.52” Frames 1, 8 & 15 show ∆RA & ∆Dec = 0. S/N is about 9.5:1 and FWHM almost too tight at 3.0”. Photometry confirms 17.8 mag.
D/1952 B1 Harrington-Wilson is a 9.2 mag comet I’d hoped to catch but got screwed up in planning as it’s very close to a 4th magnitude star and unworkable just now.
6534 Carriepeterson has reached perigee at 16.5 magnitude and 1.9 AU distance. Motion is 40”/hr. Imaged started at 21:04 hrs: 2 min, 2X2, -15C, 1 Hz.
4 X 2 min 14” Meade LX200GPS, SBIG ST-8XME with AO8
Patches of high white cloud are starting to float across the sky, and eventually cut planned imaging short at 21:36. Frames 4, 8 & 11 show ∆RA & ∆Dec = 0.
S/N ranges from 35:1 to 47:1 with FWHM extremely tight at 3” Photometry shows magnitude to be 16.4 (red).
In at 21:45. 15 observations transmitted to the MPC.
Conclusions & lessons learned:
The clear sky at twilight tricked me into believing that the transparency was excellent. It’s a puzzlement as to how there could be such opaque sky with the temperature below freezing. Had 3 misses tonight and that's pretty unusual.
Electric heated garment inside my Arctic coverall kept up with the cold, but I’d have not lasted past 22:00 if the cloud hadn’t curtailed observation earlier.
hgp logged 10 Dec 2016