Stefan Kürti´s Astro Web

Cooperation with professionals

Observational arc of minor planets and its extention

Astronomers - asteroid hunters - know very well how important role play precovery observations of minor planets. When you discover a new asteroid, there is necessary to observe it as long as possible in order to get reliable orbit. To easily recover this asteroid in next apparition you need to observe it at least in 30 days period, but you get better orbital solution from 60 days observational arc. The wayback machine does not exist, but astronomers can "travel" back in time through image archives.

When they found new object, they can return to their archival images and search for precovery positions. There is one deficiency of those archives - you cannot usually access them. But there are excemptions - one of them is SkyMorph, images database aquired during 1995-2007 by NEAT research programm. Other accessible source of images is Lulin Sky Survey archive, which consist data from 2006-2008. This archive is not so well functional as SkyMorph and there is only a fraction of images compared to NEAT. Although you can "dig" in the past for specific object here as well as in SkyMoprh.

I wrote in article Discover a new asteroid the way how to find new objects in SkyMorph data. You can search for precovery positions by the same way in order to extend orbital arc and improve object orbit.

There are still lot of hidden data on archival images which would be very valuable if someone could detect them. Precoveries are useful for all type of minor planets, whether it is a main belt astreroid, Jovian Trojan or Transneptunian object. But highly appreciated are precoveries of new NEOs. Search for NEOs positions does regurarly Rob D. Matson, USA and very succesfully. His latest detection was 2008 UV18, where he was able to find it on 2004 images based only on 5 days arc.

Cooperation with professionals

Precovery positions could be not only result of coincidence but you can search for them on purpose. In Slovak republic, Observatory AGO Modra (code 118) conduct photometry and astrometry works. In Czech republic is renown for their astrometry works Kleť Observatory (code 046, 246). As I know both of them did not use SkyMorph data for precovery works. Perhaps for lack of time. They are sticked to their research programmes and have no time for other search. This could be the advantage of skilled amateurs. After you learned the ropes of work with Skymorph, you can supply professionals with valueable data.

That is why I checked out NEAT images for asteroids discovered at Modra. And I picked up some of them. Minor planet 2004 VM15 was one of them. It had only short arc around its discovery time. I managed to detect this asteroid on plates from two days in 2002. After sending these data to MPC, they refined orbital elements of the object, further MPC linked it with some more observations from their own archive which resulted another observed year 2007. Straightaway it was easy for astronomers from Modra to catch MP 2004 VM15 on first attempt in 2009 opposition.

I was not so lucky with several other objects. The reason is apparent - very short observational period. Orbital solution based on 2 days arc is enough for rough ephemerides for week or two. When you could not extend this arc, reliability of caclulated positions decrease essentialy. And this is true for time in both directions. As the times goes, your chance to recover such an asteroid is going down.

For example for minor planet 1998 BX14 found SkyMorph searching tool several images where it should be easily find. At computed brightness it will not be difficult. Although I did not find it, although I scanned the bigger area around the supposed position. I can do nothing, just wait for another observations which improves its orbit and try again. But I can also search for it in bigger area. Contrary to professionals with busy research agenda, they cannot afford to spend a lot of time to one object, I am not in hurry and I can devote as much time to search as I want.

Precovery observations of asteroids discovered at AGO UK Modra (118)

Here I listed minor planets with precoveries in SkyMoprh archive. As a result of longer observational arc the uncertainty parameter "U" was improved, in some cases at least for 1 level, in others even for more, so a further step was made for numbering these minor planets.

Notes: in column Obs (Observatory) is listed that observatory where precovery images were taken:

644 - NEAT/Mt. Palomar
608 - Haleakala/Hawai Islands
566 - Haleakala/Hawai Islands

In two cases there were not extention of observation arc, precovery positions found on archive images lies between first and last already known observations.

Follow up observations from AGO UK Modra (118) of minor planets discovered at 644 and H06

Astronomers at AGO UK Modra help with follow up of my discoveries. Although they have their own research programm to follow, when they have an opportunity they try to images some of my asteroids. Here you can see their list up to date:

Zoznam následných pozorovaní z AGO UK Modra