Wonky trail of 2004 BL86

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Robin Scagell
Posts: 1059
Joined: Sat Jul 24, 2004 12:12 pm
Location: Flackwell Heath, Bucks, UK
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Wonky trail of 2004 BL86

Post by Robin Scagell »

I got some shots of 2004 BL86 this morning at about 00.10 UT. I decided to use a 200 mm lens on my Canon 70D, driven on my HEQ5 but not guided. I thought that the guiding would be unnecessary in 30-second shots, but I was wrong. As you can see, the trail is not straight, which on the face of it is very mysterious.
BL86_crop.jpg
BL86_crop.jpg (88.6 KiB) Viewed 1556 times
I think the reason is that the periodic error in the drive shows up far more in this way than it would normally do. Looking at an individual frame (second from bottom) enlarged you can see that the star images are slightly trailed though in the combined shot this is not evident.
BL86_crop_frame 31.jpg
BL86_crop_frame 31.jpg (63.37 KiB) Viewed 1556 times
The fact that the drive was running a little slow at this point is enough to skew the asteroid trail.

Oh well, better luck next time!

Robin
stella
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Joined: Fri Dec 03, 2004 2:41 pm
Location: 55° 57'N: 03° 08'W
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Re: Wonky trail of 2004 BL86

Post by stella »

Have you considered the possibility that its small moon is pulling it first to one
side and then to the other? This kind of 'wobble-spotting' is one way we have
of detecting exoplanets. Perhaps you have made the first discovery of a
intramoon by this method.
(Dactyl and other intramoons are available).
Robin Scagell
Posts: 1059
Joined: Sat Jul 24, 2004 12:12 pm
Location: Flackwell Heath, Bucks, UK
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Re: Wonky trail of 2004 BL86

Post by Robin Scagell »

For the benefit of others, I'm sure that Stella realises that it is highly unlikely for a 500-m asteroid to have a moon orbiting it with what would have to be a period of about eight minutes, which just happens to be the same as my periodic error! (They are 30 sec exposures with a 30 sec gap, and there are seven or eight between the same orientation of the skew.)

Robin
Vega
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Re: Wonky trail of 2004 BL86

Post by Vega »

Fascinating capture there. Nice one
Evostar Skywatcher 120/1000mm Refractor, Motor Driven EQ3.2 Mount.
Skyliner 250PX, EQ6 GOTO Synscan Mount
10x50 Bressner Bins, Canon EOS1000D, Canon S30
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