The accidental discovery of Apollo 2002BJ2 The details as to the discovery of Apollo asteroid 2002BJ2 is relatively short, but the lesson it taught me was not. I have always been interested in recovering PHAs and 1998FW4 seems to be a interesting target. At mag. 20.2, it is right at the limit of my 18" set up. The uncertainty could be +/- several degrees in either direction, that suite the wide FOV of my system too. The difficulty was that at 15 Hr RA and -15 degree Dec., it would only be visible for about 90 minutes every morning and it never rises above 40 degree above horizon. After 4 nights of trial, there was still no sign of 1998FW4, may be it was fainter than predicted. On Jan. 21, as usual there was no sign of 1998FW4 during visual blinking. And I would like to test how well Pin Point could detect other faint objects that might happen to be in the same field. So I set the mag. tab of Pin Point to an unbelievable 22 (note 1), knowing full well that at this level there will be so many possible false "loners" in all three images and it will make the auto detection take zillion of hrs to complete. To my surprise the whole process took only a few minutes (with a 2 GHz computer though) and there were a few detections. Among them was Y00C62. It's motion was about 0.87" per minute at PA 140 degree or so. The motion in RA was not too out of line, but the motion in dec was a bit high. I am no orbit expert. But from my limited experience in seeing how asteroid move in images, this mean that this asteroid may have high inclination. While this seemed interesting, I have my fair share of interesting MB discovery so I just emailed the whole batch of astrometry to MPC. As usual, Tim Spahr processed the batch really fast. He emailed me back all IDs, along with the six lines of astrometry on Y00C52 and asked me whether this object was real. With 6 positions obtained by 2 sets of triplets, I was pretty sure it was real. Upon rechecking the astrometry it was confirm that this was a real object. Pin Point indicated the mag. to be between mag. 21 to 22. I compared the flux to a known asteroid in the same images and advised Tim to change the mag. on the NEOCP page to 20.5. This is NOT data manipulation. I just didn't want to discourage potential observer that this object is too faint to observe. The weather in Jan. so far had been frustrating at 333. On a rare good night I could detect and report astrometry on 600 moving objects, and the next day only 450 could be IDed to known objects. Leaving 150 potential new discoveries. But the next night the weather was less than perfect and only 30 objects could be picked up. The whole experience was really disappointing. However, it did allow me to reflect on the method I used and in the next dark run, a totally new method to discover MB will be tested. But well all of this belongs to another article. With this kind of weather I was worry about spotting this object again the second night. Well, luck was indeed on my side this time and I did manage to pick up this object on Jan. 22 too. With only a one day arc, all Tim could tell me was that nothing normal could fit these observations, and more observations were need. On the third night it could be observed again. With a minimum of three well spread observation some meaning orbit could be tried. Tim came up with an Apollo orbit but he said more observation was necessary. So far I had not been too excited by this whole incident. I have NEA discovery in my mind and I know eventually I will discover one. But I never give this too much attention as I have other more immediate goals at this point of time. But I also have to admit that by the third day, it really got me curious as to what kind of asteroid Y00C62 could be? I had to arrive at the airport by 6 am so no more observation could be made. Luckily thanks to Tim again, Spacewatch jumped in to help. With a 4th day observation, Tim was finally able to conclude that it was indeed an Apollo. The rough orbit indicated that it has a=2.1 AU with one sigma error of 0.7 AU! It also had very eccentric orbit (e=0.66) and high inclination (I=25 degree) and H=17 or so (a disappointment at first). I got the news when I was in the New York airport. So after all I did discover my first NEA and it was a relatively big Apollo! While waiting for the next flight I draw the Earth's orbit and an Apollo's orbit on a piece of paper, just to discover something that a lot of you might already know. If an Apollo has inclination=0, it is just a matter of time that it will hit Earth. But further rough calculation showed that on average it will still take about 100,000 year for the two to collide, no wonder funding NEA search has been such a hard sell to the public. After all the dusts settled I have to confess that this discovery was pure luck. I seldom visit this region of sky and I only shot a few sets of images with hope to recover the faint PHA 1998FW4. While this effort failed, a fair size Apollo was discovered. If credit has to be given I think Tim Spahr and Bob Denny's Pin Point has to be mentioned to share any honor. As to me, it just remind me once again that how interesting this "sport" (to quote a term used by Roy Tucker) is. At the end all I want to say that I will find another NEA soon, and this time it won't be another accident, but a well plan effort :) Bill Yeung (Note 1) It is well known that with barely a few photons above the background, photometry at such mag. is not very accurate. That is why I set the mag. tab to 22, with the intention to get mag. 21 objects. This is not a problem with Pin Point.
