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Just one more main belt asteroid

Recently, I have been searching archival images obtained by the 2.5 m Apache Point telescope, New Mexico, USA. This CCD imagery was created as part of the Sloan Digital Sky Survey (SDSS) during September-December 2000-2008. It is perfect source for finding precovery observations of asteroids. In addition, it has been shown that, despite many years past since then, there are many unknown objects still hidden in the archive.

After a period of occasional searching for precovery observations of my SkyMorph/NEAT discoveries, I decided to do systematic work on SDSS images - to chceck field by field from one specific day.

My choice fell on November 11, 2001 with 1524 images in total. I used for astrometry great software programe Astrometrica. To receive more reliable result I integrated MPC Orbit database (MPCORB) from current epoch to date 2001 Nov 11. MPCORB is a database of all numbered and unnumbered asteroids orbits. After this Astrometrica accurately marked positions of asteroids on images, even those discovered recently. I also used the function for automatic detection of moving objects. In addition to the known asteroids, I found many other objects and overall measured positions for more than 1600 "new" bodies.

The advantage of the SDSS archive is that it captured objects around 22 mag. and even slightly dimmer. It would be ideal if these observations could be complemented by other observations from the SkyMorph/NEAT archive. Usually you could not detect asteroids below 20th magnitude in NEAT archive, so most of the objects identified in the SDSS are invisible to NEAT.

pis823 from obs 645, 2001 11.11, moves down. Credit: SDSS
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However, this was not the case for my object named pis823. Since it was a relatively bright of 19 magnitude, I thought it could be found in the NEAT archive. When SkyMorph displayed a list of observations, it was promising. To my observation from Nov 11 it found data from 29.10.2001 with brightness of 19.5 mag. After loading the images, I actually found a moving object in close proximity to calculated position by FIND ORB. Moreover the Know Object overlay system did not mark this body as an already known. After measuring and recalculating orbit with added positions, it was clear that I managed to confirm "my discovery". Suddenly I had a 13-days arc from the previous 4.8 minute arc. After next calculation, SkyMorph suggested images from two more nights, 23.10. and 15.10.2001. And in both cases I really found the asteroid.

I had an 18-days arc and in the next phase of my search I examined the database of single-night observations Isolated Tracklet File (ITF). This is a set of data that Minor Planet Center (MPC) could not link to any asteroid from their database. At present, this file contains more than 18 million lines (1.4 GB of data) and it is quite difficult and time consuming to work with. Thanks to David Rankin's handy NEOTK software, you can expand e.g. asteroid with 2 weeks arc to a multi-opposition object. In the first step, the NEOTK program picked up observations from October 23, 2001, which I already found in NEAT archive. Subsequently, I continued to check data back until 1994, but with no result. So I turned in opposite direction and I found one night from 2008 and another from 2017. There was nothing in the more current data until May 2019.

After this I sent the data to the MPC and I am waiting for processing. If the MPC confirms my data, just one more main belt asteroid will be added to our knowledge, so nothing extraordinary. If I am similarly lucky in identifying another asteroid out of that number of more than 1600 "candidates", it is possible that some turn to be something special eg. it will be a Mars-crosser, or even a NEO. Professional observatories discover new objects on daily basis in a big numbers. But for an amateur astronomer without access to new observations, adding one more, even main belt asteroid from archival data, it is quite a decent performance ...

2019 September 12

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