CLOSE APPROACH OF (357439) 2004 BL86

Page as of 2015 Feb 11 10:22UT

Discovered in 2004, this object appeared on the list of NEO Close Approaches to Earth in the 2015 BAA Handbook indicating a nominal miss-distance of 3.1 LD (Lunar-Distances) at a relative velocity of 15.67 km/s and expected to reach a V magnitude of 8.9 on 2015 January 27at an elongation of 179 deg.

A news note entitled, "Asteroid 2004 BL86 - a very bright close approach" was posted on the BAA News Page on January 19.

[BAA-ebulletin 00836] "2004 BL86 - An unusually brightclose-approaching asteroid" was issued on January 22 alerting observers to the forthcoming approach. A subsequent note [BAA-ebulletin 00837] announced that live-imaging would be available on the BAA website thanks to Nick James who relayed the data as a livefeed from his observatory in Chelmsford, UK.



Photometric studies made before closest approach identified a mutual event indicative of the binary nature of this system. Preliminary work indicated a rotation period of 2.62 h for the primary body and an orbital period of 13.8 h for the secondary. Subsequent radar studies by NASA from their Goldstone antenna revealed the presence of the secondary object. An announcement of the findings was made via CBET 4063.



Alexandre Amorim - visual photometry on Jan 25/26 and Jan 26/27, (Click on thumbnail for larger image.)

Tony Angel

David Boyd (high-quality spectrum) - asteroid has been reported as being of V (Vesta) type. (Click on thumbnail for larger image.)

David Briggs - prepared this chart showing the its path on the sky as seen from southern UK but was thwarted by cloud and so was unable to observe the object.

Denis Buczynski - widefield 100s exposure using 300mm f.l. Minolta lens. (Click on thumbnail for larger image.)

Peter Carson - created a 105-frame time-lapse from an imaging session between 2015 Jan 27th 00:02:38 to 00:17:34UT. All frames are 5 second exposures through a 315mm reflector at f5.3 with a ST8300 CCD on a Paramount. The field of view is 36' x 27'.

Martin Cole (visual) - He comments,

"Although at times plagued by poor transparency I did manage to observe this
object visually with an 80mm refractor having downloaded the elements into
SkyMap Pro. It was at times just on the edge of visibility in a field of
very similar brightness stars which meant about half an hour's searching
before I finally pinned it down from its motion. Fascinating to realise what
I was looking at!

Roger Drew - still and animation (60Mb) near Messier 44 (Praesepe). (Click on individual thumbnail image)

Roger comments:

The first ~6 hours were through cloud so exposures are a bit on the long side. It eventually cleared about an hour before BL86 passed through M44 so I managed to get it using 10-sec exposures. Also took a few 1-sec exposures after that until it went behind the house. I've made videos and uploaded short versions here (under Comets):

The videos are from original 3326 x 2504 fits (FSQ106,QSI683). I have a few flats and darks but did not use them for the videos. I also have C14 (F7) x QSI640 images from the first sequence (prior to M44 flyby) which are probably not of much use. The images jump periodically as the target drifted. I found I had to re-load the database a few times during the long sequence to keep the target in the frame of the C14


Gordon Ewen comments:

I thought you might be interested in this image of the asteroid I took tonight. It is 3 x 5 minute subs with a Edge 11/Hyperstar on an EQ8 mount and taken with a QHY10 colour camera.

John Fletcher - John's observations were dogged by mist and cloud. It was only during the early hours of January 27 that he managed to capture this VFMO as shown in this stack of 40-sec exposures using his 0.25-m SCT:

Sequence of 6 exposures, 02:29:43 - 02:33:42 UT, cut short by the arrival of more cloud!

Maurice Gavin reported, "failed to see it through binos, as promised, from SW London [Worcester Park Observatory] but got a record via my scope's e-finder as attached, e.g. first and last images and more in between.

Gary Gawthrope reports, "I managed to get 45 images of asteroid 2004BL86 on 27-01-2015 between 01:01 and 02:04 (when the clouds rolled in). Each frame was 60 seconds long. I was using a modified EOS500D with an Astronomik CLS visual clip-filter for Canon EOS. The telescope was a Takahashi TOA-130F (1000mm fl)."

Nick James - experiencing some of the best skies in the UK, Nick's log was as follows:

From 20:10 - 00:15, 381 frames on 11 field centres, 30s exposures, FoV
72'x54' (SXV-H9 + Megrez 72).

From 01:10 - 02:40, 41 frames on 3 field centres, 120s exposures, FoV
143'x108' (SXV-H18 + Megrez 72). Conditions go
off badly towards the end.

He was able to compare individual frames from his observing run with those obtained by Denis Buczynski (Tarbatness, Scotland) and Dave Storey (Isle of Man), each pair taken at almost the same time to illustrate the effect of parallax of the nearby asteroiod projected against the distant star background.

(More contributions to come from Nick ...)

Martin Mobberley - obtained the following image remotely, more than 1 day before closest approach. (Click on thumbnail for larger image.)

Tom Moran

Observation made between 22.28 and 22.46h UT Whitley bay England. Evostar 80ED Canon 350D Astronomik CLS CCD filter. 13x60s exposures. (Click on image for larger version).

Still image:


Alessandro Odasso

Using iTelelescope's 0.5-m f/6.7 instrument at Siding Spring, the following 60-sec exposure through a clear filter was made on January 25 starting at 14:04:09 UT. The original frame has been cropped here. (Click on image for larger version).

Alex Pratt (video astrometry)

Click image to go to one of Alex's animations:

Alex is also able to make astrometric measurements from his video frames, the advantage here is that the time-stamp on each frame is known to millisecond accuracy via GPS. Knowing when a CCD camera shutter starts and finishes is a real issue when performing astrometry of VFMOs. Video can solve this problem and very accurate astrometry is the result.

David Pugh of Clacton-on-Sea reported, "I took 12 x 3 min images of the above on 26 Jan 22.00 - 22.47UT in NW Hydra using an Astrotrac tracking mount, Canon 600D DSLR with 200mm lens at f5.6 at ISO 800 and Astronomik CLS Cllp filter. Each image produced an 8 arc min long trail of the asteroid. My reason for contacting you is that, to my surprise, if I heavily zoomed any of these images it showed the asteroid following a
zigzag course. At first I thought that I had recorded a tumbling motion of the asteroid. However, when radar imaging subsequently confirmed that this was a binary asteroid I have assumed that I have recorded the wobble of the primary caused by its satellite's gravitational attraction."

The Director was able to point out that fast-moving asteroids are sever tests of the mounting and telescope drive, since any departure from a regular rate causes apparent wobbles in an otherwise straight trail on the image. The wobble also increases the size of the stars recorded on the image but that effect is much more subtle. It turned out that David was using an AstroTrac to guide his camera rather than a telescope mount per se, hence the guiding issue.

Martin Ratcliffe

Stack of 9 x 5-sec exposures taken on January 27 05:07:07 - 05:08:12 UT. (Click on image for larger version)

John Rogers - Here's a contribution made by John using a digital camera + 200mm f.l. lens on a tripod. It shows just how bright this object became.

Dave Shave-Wall

Dave was the first to send in a report on the evening of closest approach, his being timed at 2025 UT. He set his mount to track the fast-mover, the result of which is shown below (having found a hole in the clouds to peer through!). Click on image:

Dave Storey

From the Isle of Man, Dave used a 0.4-m f/10 SCT and froze the motion of the asteroid by making 1-sec duration exposures as shown in false colour with this stack of 4 frames taken between 21:00:10 - 21:02:02 UT.

David Strange

Colour images obtained at the Norman Lockyer Observatory (NLO) illustrate the somewhat reddened appearance due to sunlight reflected from the asteroid's surface.

(Click on the left-hand image for an enlarged view)

Here's an animation from the NLO:

John Talbot

Lovely clear night for me. I took a couple of videos of it from the UK,
for example...

And a sequence of stills...

I also watched it moving through an eyepiece FOV for a while too.