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Rare occultation of a 5th magnitude star by an asteroid visible from UK on Sept 9/10 (early Sunday morn)


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I wanted to post a copy of this bulletin I received from the BAA regarding a rare occultation of a star in Taurus by asteroid Susumu.  I hope that some of you will have a sufficient horizon view to make some observations, measurements, imaging etc.  I'm not sure how high it will be in the sky at close to midnight tonight, I suspect quite low, so we need a good horizon.  I'm not sure I want to drive to Belper as it's probably an hour and if the weather is poor, it's two hours of driving wasted, but I wondered if Wymeswold -only 10 mins from me, would have the horizon needed?  I assume Belper would definitely have the horizon though, so it could be tempting??

 

I'm trying to think of ways to record an image of the event duration so that some work could be done on the data afterwards such as measuring the light intensity by a densitometer of video frames, or, if someone had a photometer fitted to their scope, carry out the photometry.  

 

The BAA bulletin is pasted below.

Good luck, Derek

 

 [BAA-ebulletin 00986] 

 

On the night of Saturday, September 9 at 23:44 UT (00:44 BST on September

10) the asteroid (6925) Susumu (mag 17.8V) is predicted to occult star

sigma(1) Tauri (HIP 21673, mag 5.1V). A detailed account by Alex Pratt of this very favourable event is available at:

 

https://www.britastro.org/node/11043

 

Given that the star is bright enough to be visible to the unaided eye, and that it is a spectroscopic binary star, many observers may be treated to a 'double' shadow cast by the star system transecting the mid-UK region. The maximum duration of an occultation from any one location is about 2 seconds when the star disappears from view. Be watchful however for secondary events, either arising from the binary nature of the star or the distinct possibility that the asteroid is a binary system too. Although the marked uncertainty in the exact location of the track is about 100 km, given duplicity in the star/asteroid, observers several hundred km either side of the centre-line should watch for a positive occultation event. Likewise, start observing a few minutes ahead of the due time and continue a few minutes after too in order to capture unexpected phenomena. Note that the star is in Taurus and will be fairly low towards your eastern horizon.

 

Do please make every effort, weather permitting, to observe this especially rare event. If you are able to use a video camera hooked up to some form of optical aid then do consider using it, as this type of permanent record is invaluable observation-wise. Visual observers should also attempt to time the event, both the duration of the disappearance and the absolute time if at all possible. An easy way to add time marks to your video record (say after the start and before the end)is to momentarily shine a flashlight or similar near the entrance of your optics, synchronising the flash as accurately as possible to some reliable time signal.

 

Good luck everyone!

 

Richard Miles

Director, Asteroids and Remote Planets Section

2017 September 07 09:24 UT

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weather looks good for Belper but unsure if they have a fixture on today, if so they may well be in the bar afterwards. I'm sure software can figure the relative brightness especially if there is a known brightness source in the same fov. I'm not sure how to set it up but LT Image can give distances, luminosity and angular separation.

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yes, free from the Liverpool telescope. It's a bit basic as far as imaging goes, it's made for schools. But some of the other functions of it are really good, very simple to use too.

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Excellent.  I'll look it up and get.  Thanks.

 

BTW, in my post above, I mentioned close to midnight - that is in GMT, so the actual event would be 00:44 BST, but it is mentioned in the post too.

 

Looks like it will be about 17-18 degrees high from my location.  If I can see Aldebaran, then I might just get the 5th star underneath it.

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Its too low for me if my calculations ,via stellarium, are correct - 23.44 would put it at 6 degree above horizon - right in my distant tree line plus light pollution. Good luck to everyone who tries.

 

Plus Mr Blobby will be at 21 degree to the right by 15 degree's

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That's very interesting Derek. :thumbsup:

 

2 hours ago, stash said:

Its too low for me if my calculations ,via stellarium, are correct - 23.44 would put it at 6 degree above horizon - right in my distant tree line plus light pollution. Good luck to everyone who tries.

 

Plus Mr Blobby will be at 21 degree to the right by 15 degree's

Clive, I think it is at 00.44 BST (after midnight) which would put it 16 degrees above your horizon. Would that clear your trees? It is just a degree below Aldebaran. :)

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If you can see Aldebaran, the star is just underneath (or possibly at that time of rising, may be to the lower left).  In Stellarium, with a 300mm on my 1100d, if I got Aldebaran in the FOV at the top middle of the landscape orientation, the star should be in the same FOV. But if it's clear, I intend to hopefully frame the star as close to the middle of the frame as I can.  If anyone else can image it at another location, I think data can be used to generate the shape of the asteroid, although I don't know how many locations are needed.

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23 minutes ago, Tweedledee said:

That's very interesting Derek. :thumbsup:

 

Clive, I think it is at 00.44 BST (after midnight) which would put it 16 degrees above your horizon. Would that clear your trees? It is just a degree below Aldebaran. :)

Yeh I read Derek's adjustment to the time. Yep above trees but MR B will be in full flow and anyway the clouds are moving in - some much for a clear night.  Might have a look thru the Bino's 

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The red box shows the FOV of my 300mm lens on the 1100d camera, roughly anyway.  Sigma1 tauri is under Aldebaran.

sigma tauri.jpg

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3 minutes ago, stash said:

Yeh I read Derek's adjustment to the time. Yep above trees but MR B will be in full flow and anyway the clouds are moving in - some much for a clear night.  Might have a look thru the Bino's 

Clouds drifting over Mansfield with the odd gap showing stars, but my forecast is for badly deteriorating seeing and transparency over the next few hours looking pretty bad by the time of the occultation. If I'm still up and it's clear, I might go to my nearby park because I can't see that low in the east from my backyard.

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1 minute ago, Tweedledee said:

Clouds drifting over Mansfield with the odd gap showing stars, but my forecast is for badly deteriorating seeing and transparency over the next few hours looking pretty bad by the time of the occultation. If I'm still up and it's clear, I might go to my nearby park because I can't see that low in the east from my backyard.

Its saying 100% humidity at about 00.30 onwards - thats water droplets - so fog/mist and where I live the east of me will be crap (tech term!) still if I haven't fallen asleep I might have a go - good luck.

I didn't see the Aurora either last night :(

On the good side I just had fresh Bramley apple and custard - HMmmmm

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I've just had a look out.  I can see Aldebaran above the roof tops easily.  With 10x50 bins and no dark adaptation, I could see sigma tauri under Aldebaran. There is a pair of stars, sigma 1 and sigma 2.  Looking good.

 

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I managed to get some video. Dratted mobile phone clock, which I synced with the PC synced on Dimension 4, hung up whilst I was waiting to trigger the video. I now don't know if I was too late, the phone updated the clock time (previously stuck on 00:42), jumped a few minutes. I hate it when that happens.  I need a better reliable clock than a mobile phone.

 

Looking at the video, Aldebaran can be seen easily, and the two sigma tauri stars can just bee seen in play back. But they scintillate, which I guess will interfere with the occultation - say if the star goes out due to atmospheric twinkling at the same time as the occultation.  I also think I need to extract crops to enlarge, and possible invert to negative, or both.

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Well done making the effort. :thumbsup:

 

I take it you stayed at home then. Post the video up so we can have a close look. 

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Thanks.  The video is over 1 Gb. Not sure how to handle it/upload it.  Just ran PIPP, 14300 frames ouputted.  Not even sure if the frames were cropped in the right place.  I used AOI and AFB.  Here's a single image of the area just to show readers of the close proximity with Aldebaran

IMG_5796-sigma 1 tauri.jpg

Edited by Orion
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Good luck with that. Hopefully there is a second or two with a big scintillation where the star actually disappears. :)

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Just got up. It's still uploading after 10 hours, showing another 2.5 to go. If you let me have your email address, I can share the folder with you and you can have a look.  I think you're right, I was thinking scintillation could be regarded as a sort of noise due to changes in refractive index of the air - not necesarilly in a random manner. But, lets say it was random around that time. I took about 7 minutes of video, so in that time, the scintillations (light or dark) could be averaged and subtracted from the overall intensity - say if one could extract intensity data of pixels going through the star.  May be scope there?

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Video was succesfully uploaded to my Google Drive.  I don't understand the workings of Google Drive, but I have other stuff on there, not relevant to astro. But I would only want to share the astro video. Do I just be selective in sharing a file, or folder? Is it possible that other stuff can be seen if files are in the same folder?  (I suppose it might depend on whether the file, or folder has been shared does it?).

 

If anyone can work on the video, do please collaborate with me on it.  I may have been successful in inserting a time marker on the video, by quickly waving a red LED light past the lens front, whilst watching the time on my mobile phone, previously synced less than an hour before the event, with Dimension 4.  But it may have been on a trial video before the actual event video. I hope not.  The first red flash signals 00:42 BST.  The second red flash signalled 00:52 but has an uncertainty of at least 5-10 seconds due to mobile phone issues (I don't think the clock advanced to 00:52 when it should have, due to some notification that came in.  I hestitated before I swung the red light, so the 00:52 might represent 00:52:(+05-10s), possibly.  

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Got the video thanks Derek.

 

Going to have to study it closely in a darkened room. I see what you mean about the scintillation. 

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The bright star at top is Alderbaran mind.  Sigma Tauri double is closer to the centre of the frame.  First red flash = 00:42 BST.

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