And once in a while there's a screwup

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Astro Day Coordinator
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Joined: Fri Jun 13, 2003 9:03 pm

And once in a while there's a screwup

Unread post by Pete »

Wednesday, 14 Nov 2012

The sky’s clear in the afternoon and I’m out at dusk shooting a new set of sky flats using my usual bastardized tee shirt / twilight setup – something that usually doesn’t work really well, but it’s the best I’ve been able to come up with. It’s in the low 40s so to while away the time ‘till observing the camera’s set to run a series of -30°C bias & dark frames to replace frames from 2009.

2012 TA219 is a 1.7 km sized Amor now 18.7 magnitude and .6 AU distant. Discovered 34 days ago, uncertainty level is 5 and RMS residual is 0.49 Apparent motion is 1.9’/hr. Imaged from 18:36 – 19:18 hrs at 3 min exposure, 2X2 binning, -30C cooling, 1 Hz guiding. Frames 1, 3 & 5 show dRA = +0.4’ and dDEC = +0.1’

46362 is a 17.9 mag main belt asteroid in the same frame as 2012 TA219. 12.6 km in size and 2 AU distant, motion is 32”/hr and residual RMS is 0.52” Frames 1, 5 & 10 show dRA = +0.1’ and dDEC = 0

5587 is an 11.5 km sized main belt asteroid now 1.2 AU distant and shining a relatively bright 16.8 magnitude. RMS residual is 0.49”, and since my RMS residual is about 0.3” and since 5587 is on the MPC’s critical object list it’s a good target for Wishing Star. Motion is slow, at 1.8’/hr, so a longish exposure won’t hurt anything and will give me a better chance of picking up a discovery. Imaged from 19:35 – 20:27 hrs at 3 min, 2X2, -30C, .5 Hz. The 2 second guide rate is ‘cuz I’m guiding on a 13th mag star. And as luck would have it, 5587 is occulting a star. Frames 1, 7 & 10 show dRA & dDEC = 0.

8761 Crane is an 18.1 mag main belt asteroid now 2 AU distant. With an RMS of 0.54 it’s worth reporting. More important, it’s in the FOV from 5587. It too is occulting a star. Frames 1, 8 & 10 show dRA and dDEC = 0.

2012 TJ146 is a 19.2 mag Apollo now .23 AU distant and moving 1.4’/hr. And it’s in the same FOV as Uranus! First time ever I’ve encountered a planet in my relatively tiny FOV while working an asteroid. Discovered 33 days ago, TJ146 has an uncertainty level of 5. Imaged from 20:41 – 21:43 hrs at 3 min, 2X2, -30C. Titan is visible but the other moons are lost in the blooming. Screwed up here as I forgot to set the reduction, so the images are quite noisy and sub-par to work with, and require significant stacking. Here’s the data reported:
Frames dRA dDEC S/N FWHM
1-5 +0.3’ 0 4.8 6.2
8-12 +0.2’ 0 3.9 3.6
14-19 +0.1’ 0 7.5 6.2
The MPC subsequently rejected this data set because of inconsistencies in the measures, as determined by their departure from the calculated ephemeris. Shame on me. These weren’t robust images and what signal there was happened to be scattered over a whole lot of landscape. Furthermore, I should have picked up on the variation in dRA. That would have tipped me to the probability that I was chasing a ghost.

2012 VE37 is a 477 meter sized Apollo now 19.4 magnitude and .34 AU distant. Discovered only 7 days ago, it’s uncertainty level is 9 and its motion is 3.4’/hr. Imaged from 21:57 – 23:01 hrs at 90sec, 2X2 binning, -30C cooling, 2 Hz guiding. Stacking, frames 1-5, 6-10 & 11-15 show dRA = +0.4’ and dDEC = +0.2’ There are several other asteroids in this FOV. Air temp’s down to 33F, and most of the astrometry I’m doing now is remote from inside the house.

83830 is in the same frame as 2012 VE37. It’s an 11.5 km sized main belt asteroid now 2 AU distant and 18.0 mag in brightness. Moving slowly at 32”/hr, its residual RMS is 0.58 Frames 1, 11 & 21 show dRA = +0.1 and dDEC = 0.

193608 is also in 2012 VE37’s FOV. This 4.4 km sized main belt asteroid is 1 AU distant and 17.5 magnitude. Motion is 36”/hr and RMS is 0.48 Frames 1, 11 & 21 show dRA = +0.2’ and dDEC = +0.1’

171086 is also in my FOV with 2012 VE37. This is another main belt asteroid 5 km in size and 1.7 AU distant. It’s 19.2 magnitude and has a residual RMS of 0.53 In the early exposures it’s occluding a star. Stacking frames 15-19, 22 – 26 & 27-31, dRA = +0.1’ and dDEC = 0

Air temp is down to 32F at 23:07 hrs as I close up the dome and head inside to transmit a total of 27 observations to the MPC. There was a lesson learned but it's unfortunate that 3 observations were bad…………

hgp belatedly logged several days and 2 clear nights later on 20 Nov 2012
Pete P.