An Audience with 2004 Bl86 Near Earth Asteroid

Having recently signed up online with American astronomy magazine “Sky and Telescope”, I received a notification that Earth was to have a close encounter with an asteroid on the evening of Monday 26 January, and that it would be visible from the UK.

Not really thinking that we would stand a chance of seeing a Magnitude 10 object in Chesterfield, I nevertheless contacted John Brown and asked if he would like to join me and try to find it; I also asked Sue Silver to put an APB out to the general membership inviting them to join us if the sky was clear.

In preparation, I read the “S&T” article online, and printed off the map showing the object’s track (passing to the right of Hydra’s head, and then upward through Cancer), and stars shown down to 9th Magnitude. The map was based on a viewpoint from the centre of the Earth, so I cobbled together a correction for our viewpoint in the UK with the aid of a planisphere, a globe, a calculator and the map pinned to a wall.

Shortly before I left for the observatory, the online weather forecast didn’t look good between 8pm and 11pm, with cloud predicted. However I decided to proceed, and I arrived at the observatory at about 7.30pm. Pete arrived shortly after, and he set up the scope while I made coffee.

We pointed the 18”scope (using a 32mm plossel) at Jupiter first, which was a bit fuzzy but otherwise steady. I collimated the finder with the scope. We went outside and saw that it was clear, but with the light pollution we could not find Cancer with the naked eye, and the only two stars we could see near the asteroid were the bright ones in Hydra’s head. We lined up on one of these, and using the finder I started to star-hop between the faint stars indicated on the map (which was difficult because the finder view was reversed). John Brown, then John Bardwell, arrived in the meantime.

At about 8.30pm, after some breaks from the eyepiece and a couple of cups of coffee, I settled on two stars that I thought were close to where the asteroid would be at 9pm and I left the scope tracking. We had another break, and we went into the lecture room, immediately ruining our night vision!

At 8.55pm I looked through the eyepiece (yes, amazingly it was still clear despite the weather forecast), and at the top right edge, I saw a star that I hadn’t seen earlier. It was difficult to tell if it was moving so I asked for Pete’s opinion, and he looked and thought that it was. When I returned to the eyepiece, it had clearly moved downwards in the field of view. We had found the asteroid! I called the two Johns into the dome and we took turns to watch it drifting through some star fields for the next hour or so. Pete noticed that the asteroid faded and brightened on a regular basis – perhaps it was rotating! At 9.55pm John Bardwell was at the eyepiece and noticed another body crossing the field of view from left to right. It was travelling only slightly faster than the asteroid so it stayed in the eyepiece long enough for us all to see it. So far we don’t know what it was, but Paul Money later confirmed that he saw it as well.

At just after 10pm, we called it a night, all having seen something new - an asteroid (possibly two?) motoring through the Solar System!

(Sorry Folks, our attempts to get photos of it failed)

PS the video is just an artist’s impression of our first view of it.

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