Asteroid (6925) Susumu to occult a mag 5 star

[Alex Pratt]

At 23:44 UT on the night of September 9 ( 00:44 BST on September 10) the mag 17.8 asteroid (6925) Susumu is predicted to occult the mag 5.1 star sigma1 Tauri (HIP 21673,  UCAC4 529-009019).                                       

(6925) Susumu / HIP 21673 event on 2017 Sep 09, 23:51 UT

The target star, which is located near Aldebaran, could be occulted for up to 1.8s causing a temporary drop in brightness of 12.7 magnitudes. This short duration is ideally suited for video or drift scan recording. It should also be an attractive event for visual observers using minimal optical aid.                                                              

The predicted ground track passes over or near Snowdonia, Chester, Liverpool, Sheffield, Leeds, York and Hull, although it’s worthwhile observing from a location 100km either side of this region.                                   

It’s suggested that attendees at the BAA Chester Weekend could monitor the event in groups of widely-spaced observers, several km apart. Note that the star’s altitude will only be about 14 degrees.

Clear skies,

     Alex.

[Jeremy Shears]

More details in the BAA article by Alex on the front page of the BAA website.

We have arranged for members who may be staying in Chester overnight on the Saturday/Sunday of the Chester meeting to observe from a farmer’s field in the village of Waverton, 3.5 miles south of Chester. This is just on the S edge of the predicted track, but the track has some uncertainty associated with it. This is a rural location and people wishing to observe from here need their own transport and instrumentation.

[Tim Haymes]

Alex suggests my web pages in his note https://britastro.org/node/11043#overlay-context=node/11043
These pages were written some time ago, but still offer some ideas to follow up like “Drift Scan”. I did some experiments with this (Detailed How To section 17) using a 300mm lens and a simulated occultation.  I suggest this might be a usable method to record it with a DSLR and an un-driven optic. I hope someone will see the occultation and time the start and duration of the event.  I wont be observing this (too far away) but I look forward to receiving any results (negative or positive) by whatever means is available – best of luck and my regards to the Chester group.

[Richard Miles]

I suspect that this could be much larger than depicted on the supplied map and that observers much further afield should try to observe this very bright star disappear momentarily (for up to 2 seconds). Asteroid occultations of ‘naked-eye’ stars visible from the UK are extremely rare and so, if clear, I recommend observers trying for this. Use optical aid, or better still video recording, together with as large an aperture telescope or other optical aid as is convenient. Naturally timing the disappearance and reappearance would be good, and do remember that the asteroid may actually be multiple (we do not know this however) and so watch out for the star to potentially disappear TWICE – you never know.

[Alex Pratt]

The prediction lists the target star as ‘possible double star’. Let’s hope we obtain timings and light curves of this event. Please observe even if you are 100km distant from the predicted shadow zone.

Clear skies,

     Alex.

[Lars Lindhard]

No occultation in Esbjerg, Denmark.

[Alex Pratt]

Thanks for your report, Lars.

I had good weather and recorded the target field for 5 minutes centred on the predicted time. No occultation was detected from Leeds. I’ll put a summary report on my Member Page.

Hopefully some observers had a positive result to help define the path of the shadow zone.

     Alex.

[William Stewart]

Observed (recorded video) for 2 minutes either side of the predicted time from Ravensmoor, Cheshire (21km outside shadow path) – alas no occultation detected.

Best regards, William

[Richard Sargent]

Hi Alex,

Observed via video cam on telescope from about a minute and a half before predicted time to 3 minutes after but no occultation seen.

Regards,

Richard

[Alex Pratt]

Hi Richard, William,

Thanks for your confirmations of a miss from you locations.. 

Tim and I haven’t received a positive report, yet. The hunt is still on for the shadow track!

Clear skies,

     Alex.

[Alex Pratt]

Oops, I was going to attach an occultation report form template, but the website doesn’t support uploading txt files.

Clear skies,

     Alex.

[Peter Mulligan]

Hi Alex

I took a series of  images  of  Sigma1 Tau with my Canon 1100d with a 250mm FL lens between 23:43-00 and 23:45:00UT, 0.250sec exposures, at ISO 6400, I looked through all the images the stars light was constant, But then I suppose I was aiming for a lucky shot, there was a 4sec interval between my images so I would have probably missed it!

Peter Sheffield

[Tim Haymes]

Looks like Richard (Chester) was closest to the track – inside by 1 km, while Alex and Stuart were North and South respectively by about 1 path width. I have observations from Great Yarmouth area where there was a small possibility (S Hubbard, A Robertson). Both report no occultation. Lars (Denmark) you were about 2 path widths North of the predicted track. I have one other video observation from Derek Robson and your data is being looked at.

Alex and I will be at ESOP36 in Germany 5 days over this weekend so there may be a lull in feedback – Thanks to all contributors and to Alex for the alert for this event.

[Lars Lindhard]

>Lars (Denmark) you were about 2 path widths North of the predicted track.

Yes, 67 km north according to the prediction. I observed from 23.43 – 23.50 UT and nothing happened. About 23.50 clouds came in and covered the sky. 

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