The new discovery appeared in MPEC 2012-T11 today as 2012 SM58 (packed designation: K12S58M). It is a high-inclination main belt asteroid.
On September 21, I was using SSON's 61-cm Cassegrain in search of an object discovered by another observatory, when I noted a faint mag. +19.5 object moving near the upper edge of the images. It is indicated in the blink below (which shows only part of the original images):
The images were made at a high declination (+35 degrees) well away from the ecliptic. A check showed that no known object was at this position. So, a new, high inclination asteroid? At first I was not entirely sure. The object came out of the glare of a bright star, so it was a possibility that it was a reflection in the telescope's optical system. In the first of the 4 images (taken 15 minutes apart) it was difficult to see, probably because it was closer to the glare of the star. After measuring it in Astrometrica, and trying an orbit fit with FindOrb, it did however seem to fit an asteroid orbit.
I decided to wait until I had been able to image it a second time before sending in the observations to the Minor Planet Center. Bad weather on the two telescopes I use (in Arizona and California) however meant it took six days before I could image it again, on September 27th. With a Vaïsälä orbit fit to the Sept 21 observations to go by only, 6 days is already enough to create clear positional uncertainties. I was lucky though: the object was visible (near the image edges) in the new images.
While I was quite sure it was the same object, FindOrb initially had some trouble linking the 21 Sep and 27 Sep data, so I decided to send in both sets under different temporary designations: LaMa 502 and LaMa 504. The MPC sent me back a message indicating they thought it concerned the same object: " LaMa504 (LaMa502 "
More bad weather and the entry of a full moon next again prevented new observations, untill I was able to image it again on October 4 and 5. Below is the blink of the October 5 images:
The new discovery appeared in MPEC 2012-T11 today as 2012 SM58 (packed designation: K12S58M). It is a MBIIb asteroid with an inclination of 21 degrees. Orbital elements (from the MPC):
Epoch 2012 Sept. 10.0 TT = JDT 2456180.5 MPC
M 344.68019 (2000.0)
n 0.21885053 Peri. 110.11057 T = 2456250.50125 JDT
a 2.7271204 Node 273.19478 q = 2.3235562
e 0.1479818 Incl. 21.08086
P 4.50 H 16.7 G 0.15
Assuming a typical albedo, the absolute brightness of H 16.7 suggests an object about 1.5 km large.
The orbit in our solar system: