Opposition of 433 Eros and the solar parallax

[Steven van Roode]

Only yesterday I realised that the next opposition of asteroid 433 Eros in late January 2012 will be a close one. For the first time since 1975 the asteroid will get as bright as magnitude +8, making it visible in small telescopes.

Such a close encounter did remind me of the 1901 and 1931 apparitions, which were then used to measure the parallax of Eros, and ultimately that of the sun. The value of the solar parallax obtained during the 1931 opposition (8".790) was held to be definitive until 1968, when radar measurements took over!

So, there's this exciting opportunity next year to measure the sun's distance twice using two classic and historically important methods: the transit of Venus on June 5-6 and the opposition of Eros on January 31. This also lets us compare the accuracy of both methods.

By taking simultaneous pictures of the asteroid from different places on earth during the last days of January, its parallactic displacement can be measured. If you would like to join this project and perform this unique experiment together with others, please drop me a message. I know it's on short notice, but it's not too late to get things organised!

[Demonperformer]

That sounds like a really interesting project. What sort of photographs would we need to be able to produce? I only have very basic photographic abilities atm.

[Ags]

Sounds interesting, but I also only have basic capabilities. Mag 8 does not sound too demanding though, although reference stars may well be fainter.

[Steven van Roode]

I still have to work out the details, but I think basic photographic abilities should be sufficient to participate in the project.

The aim is to photograph Eros simultaneously from different locations, with some clear reference stars within the field of view. It shouldn't be too difficult to find out up to which magnitude stars have to be captured to get a good set of reference stars on the photographs.

[Demonperformer]

Just checked its position on 31 Jan through MPC. Looks like it should be quite an easily identifiable field. There is a triangle of 9th mag stars west, with a pair of 9th mag stars east. There is also an 8th mag star north of its position and a 7th mag star to the south, all within a 1.25 degree fov.

[lukebl]

Thanks for the heads up. I'm always fascinated by the asteroids, and as you say this is the best opposition of Eros for years (I am old enough to remember the 1975 opposition being mentioned in Sky and Telescope, and I think I even observed it then with my childhood 70mm refractor. must dig out my old copy of S&T and read that article). At opposition it will be motoring along at a rate of 160" per hour, at a distance of around 27 million kilometres

Did this quick chart showing its apparent magnitude for the next 20 years. As you can see, it fades rapidly next year to around mag 15 but will be nearly as bright again in 2019, then won't be that bright again for a long time.

[Steven van Roode]

I made a finder chart for Jan 30 (12 UT) until Feb 1 (12 UT), more or less centred around the moment of perigee. This most likely will be the period for coordinated imaging of Eros to determine the parallax.

The map data is from TriAtlas, the positions of Eros are computed using JPL online Horizon tool (both J2000.0). Is this looking any good? Suggestions for improvement are very welcome!

[lukebl]

Really interesting stuff. We will clearly need to be co-ordinated so that we take our images at precisely the same time. Assuming the skies are clear, would an image taken precisely on the hour (i.e at, say, 22:00, 23:00, etc) be satisfactory?

Over to you to organise us all!

[Ags]

We need to schedule several shots, for example every half hour. That way can get more data and also maximise the chance of a gap in the clouds for all of us.

[Steven van Roode]

Right, we need several times to accommodate for gaps in clouds, etc. But we also should be aware of observers at other places on earth. If we are to create a long baseline, other observers should be far away (like India, where a considerable group of individuals has already showed interest in taking part in the observations, or the USA). In order for all these observers to be able to see and photograph Eros simultaneously, some convenient times should be chosen.

I should look into this with a planetarium programme, but I guess it would be around 0 UT.

[Steven van Roode]

Michael Zeiler made some images of the earth as viewed from Eros for me. These helped to find some good times at which Eros is to be photographed on January 31 (or January 30, or February 1):

The night side of earth is, for clarity, made light, while the day-side of earth is darker.

At 7:00 UT North and South America will provide a long north-south baseline. At 18:00 UT Asia and Australia will both see Eros (though low in the sky). At 23:00 observations from Europe, India and Africa can be made.

[Steven van Roode]

Detailed instructions are now online! For links to the announcement of the project and the instructions, see this thread of the Astronomy Activity group: Yahoo! Groups

[TycoFrance]

Hi Steve,

I surprinsingly found up your post with Google research. Indeed, we have already engaged in France several experiments on the Eros Parallax since Autumn 2011.

It follows first measurements made on Mars in January 2010 :

Mesure et interprétation de la parallaxe de Mars | Les Expériences d'Aphélie

(unfortunately it's in French !)

So I subscribed to the forum to invite you (or other volunteers !) to join us for the future experimentations we are considering now.

We have several volunteers in Reunion (Indian ocean French island) and in France and Greece, and two automatic telescopes available.

The first results show that we are capable to measure the AU with an accuracy better than 1%.

We are programming now several experiments in January or february. But the poor weather won''t help us !

The idea is to make at the same time 15 seconds photo synchronized with the GPS time and to measure the parallax with astrometric measurements. We'll make probably these photos a Friday or Satursday evening.

So don't hesitate to join us and we'll send you a email alert if you want to participate. My mail is lauboudetatyahoodotcom

Best regards,

Tyco

[Steven van Roode]

Thanks for this. It seems that our initiatives are nearly identical. I invite you to submit your data to our project as well.

Our Eros Parallax Project runs from January 28 to February 3. Each night at 7, 18 or 23 UT you take a picture of Eros. Then you process the picture with free and online software, and subsequently submit the obtained data through a form on the website. There's also the possibility to send in your pictures, as to create a depository of all pictures taken across the world.

Submitted data (location, date and time, RA and Decl of Eros) will be available to everyone.

Detailed instructions and the submission form can be found at Eros and the solar parallax | Venustransit

I'm looking forward to your contribution!

[shd01]

Hi all,

I too had my own project before stumbling upon this post. I plan to use diurnal parallax, which will be thirty-something arc seconds at my latitude.

In the lead-up to opposition I've been using a Canon DSLR on a fixed tripod with a 75mm lens. This detects the asteroid, but only on moonless nights.

My pictures to date haven't been taken at the prescribed times, but I'm happy to share them anyway. Here's one with a Sky Charts overlay.

I'm keeping a log of my observations on my livejournal page.

[TycoFrance]

It seems that's the weather will be clear in the next days in France (and very cold...)

We have programmed to take pictures of Eros with our partners of the Reunion Island (French island in the Indian Ocean).

We will take pictures between 22h TU and 23 TU each minute, synchronized on the GPS clock, wednesday February 1st... (that is to say, tomorrow !) We will take pictures the next days if the sky stays cloudy...

So be ready !! ;-))

TycoFrance

[Demonperformer]

Hi

I posted a thread on the imaging section about this, but it has not generated any responses. So has anyone used Astromety.net, because I can't get into the dashboard, and my eros picture from last night is just a picture in search of some data?

The thread I posted is here

Thanks.

[themos]

We took lots of shots of Eros last night, from midnight onwards. We used an 8 inch SCT at its normal focal length and DSLR exposures of one minute and half minute. The images can be solved by astrometry.net (to our relief). Lots of data reduction to do...

[TycoFrance]

We have succeeded to take images of Eros from Paris and Reunion Island yesterday evening !

But it was very cold and windy ! -8°C and 40 km/h of wind...

But some images are good...

Tyco

[themos]

This is what it looked like last night from Oxford, there are some dodgy frames in there but also some good ones. The bright star on the right is TYC 4918-1211-1, mag 8.5, the one on the left TYC 4918-1305-1, mag 11.

[themos]

This is what a successful astrometry solve looks like. There is an RA/DEC grid, two stars that are circled in green and Eros circled in red. The circles are centered on the centroids of the image blobs and the little red diamonds in the stars are the positions as stated in the Tycho catalog, providing a visual confirmation that the astrometry is accurate. The coordinates of Eros are printed in red.

[michael.h.f.wilkinson]

This is what it looked like last night from Oxford, there are some dodgy frames in there but also some good ones. The bright star on the right is TYC 4918-1211-1, mag 8.5, the one on the left TYC 4918-1305-1, mag 11.

Really nice footage! Must show the kids that.