There are already two threads with some info on this upcoming occultation of Pluto, so I thought to condense the info into one place for those who are interested.
The original predictions, from IOTA, the RIO group, and MIT are attached.
Both predictions are converging somewhat, in that the MIT prediction has moved a bit north, and the RIO prediction has moved south. Interesting times !
The casual reader will perhaps note that these predictions are fairly widely divergent. It is not possible to say at this time which one is the most correct; so any observer between Indonesia and Antarctica is in with a chance for the event, and should consider observing.
The last link above, from MIT, has a very good section on Observing Notes. Well worth reading. This section may help to answer the difficult question on filters, observing times, etc; although the prediction is for NZ and Tassie it is worth reading for anyone in the souther hemisphere.
Jay Pasachoff from Williams / MIT also writes on the planethunters blog, with some very nice info on previous occultation results and what people are looking for with the June 29 occ.
Tony - I'm somewhat astonished that the occultation path & timings cannot be more precisely defined in advance - we're not looking at a mere asteroid (Pluto used to be a bloody planet!).
Can New Horizon's emergent approach data be used (not by us mere mortal amateurs!) to refine geometries?
Can New Horizon's emergent approach data be used (not by us mere mortal amateurs!) to refine geometries?
I think it is the other way around. New Horizons needs accurate telemetry, and an occultation of a fixed star by the planetoid can go a long way to better aiming the space probe at the space rock.
I think it is the other way around. New Horizons needs accurate telemetry, and an occultation of a fixed star by the planetoid can go a long way to better aiming the space probe at the space rock.
That is exactly right. And that is why it so crucial to observe this event - it will provide data for any final adjustments that need to be made to New Horizons as it approaches Pluto.
Dean - I found this out a few years ago and was as astonished as you. I think some of the problem comes from the huge swing between Pluto and Charon, with the barycentre outside the surface of Pluto. Have you seen that animation of them orbiting each other? Huge wobble. This is also part of what makes Pluto so interesting!
Steffen and Jacquie have answered better than I could. And yes, it seems astonishing that we have such a poor grasp of the orbit of Pluto, and such a poor knowledge of the position of the occulted star.
But that is the current state of play.
When Gaia finishes its observing run an a couple of years, our astrometry will be ten times more precise than what we have now.
Also you may consider that Pluto has (as far as I know) the best determined orbit of any of the objects beyond Neptune. At least the uncertaintly is only about one planetary diameter. So there is still an awful lot of work to do even in the solar system to refine our knowledge, and this is work that amateurs can play a pivotal role in. Occultations of trans-Neptunian objects benefit greatly from amateur involvement. We may not have the biggest scopes or the coolest cameras, but there are enough of us to spread out widely and refine these orbits in a way that the professional astronomers cannot do.
As far as the info from New Horizons being able to refine our knowledge of the position of Pluto ... the uncertainties in all spacecraft motions require "mid-course corrections" at points along the way. So New Horizons' position is being refined as it gets closer to its target, which is good. Unfortunately, the occulted star's position is still not as well known. Astrometry is probably the biggest source of error, with the Pluto orbit being second. The post from MIT mentioned above has astrometry on the target star to about 29 milli-arc-sec, which is pretty good, but all the errors could push the path north or south by more than 1000 km (1 standard deviation of the error = 1097km).
The bottom line - observe first, and settle the question with direct measurements.
Regards,
Tony Barry
WSAAG
Last edited by tonybarry; 31-05-2015 at 10:52 AM.
Reason: added bit about New Horizons refining orbit
Yes, you have the times right. The error in time (due to the prediction uncertainty) is a bit less than one minute. The occultation duration has a maximum of 99 seconds. The disparity between predictions is somewhat larger :-) so for safety, you would choose to observe for around five minutes either side of central time. I realise that would be difficult for a visual observer, but magnitude 12 stars would be doable in that 40cm Newt ! The magnitude drop is around 2 full magnitudes, so it would be easily noticed. The ingress and egress are not sharp, so you must consider that; more like a fade away than a turn off the lights.
Yes, you have the times right. The error in time (due to the prediction uncertainty) is a bit less than one minute. The occultation duration has a maximum of 99 seconds. The disparity between predictions is somewhat larger :-) so for safety, you would choose to observe for around five minutes either side of central time. I realise that would be difficult for a visual observer, but magnitude 12 stars would be doable in that 40cm Newt ! The magnitude drop is around 2 full magnitudes, so it would be easily noticed. The ingress and egress are not sharp, so you must consider that; more like a fade away than a turn off the lights.
Regards,
Tony Barry
WSAAG
Thanks Tony, I will give it a try weather permitting.
12 mag stars no problem for my scope.
My "Sky6 program gives a 12.2 star in that position and is occulted around that time,so will print off a chart and get the ARGO NAVIS to do it's thing and see how I go.
I have only ever had one successful Asteroidle occultation that is mainly due to the weather.
Fingers crossed.
Cheers
For an asteroid (or Dwarf Planet) Occultation Observer, OW is a must-have software. It does the following;
- It automatically keeps up to date with the various prediction websites, and condenses all the info into one place where it's easily sorted.
- you enter your site coordinates, and it presents event criteria unique for your site; e.g. event time, target atlitude and azimuth etc.
- allows the observer to 'announce' their intention to observe an event. This is then propegated to all other announced observers, so everybody can see what is going on.
- allows printing of finder charts (two clicks) from C2A if installed.
- sends reminders via email and by on-screen messages if you are using the PC at the time.
- is linked into the reporting process to improve the quality and timeleness of the reports.
- and a host of other helpful features.
- and it's created by an an Aussie - Hristo Pavlov.
It is interesting that the MIT prediction has moved north, to encompass Melbourne and perhaps up to Euroa; while the RIO group prediction has moved south, with the northern limit a bit north of Brisbane.
While it's obvious they cannot both be correct, it does illustrate how difficult the task of such predictions can be; and the best advice is to observe if you are anywhere in the right hemisphere.
I have added the prediction images to the first post of this thread.
FYI...
Here is the latest Epheremis.. It has moved further south as per Bruno Sicardy a world renowned reputed Occulatation tracker (from France - see his page, its amazing) working w/the Brazilian folks.. dated June 14th.. So probably just in Tasmania (if at all).. see the latest ephemeris below..
There are many in the South Island imaging the event (if no clouds).. The RASNZ Occultation Section headed by John Talbot knows also the current info..
Also the BOOTES-3 telescope in Blenheim (South Island, New Zealand) is going to image it.. they too can advise the current ephemeris..
Who am I ?.. name: Raj Pillai an avid Pluto fan a co-admin of one of the most well read Facebook Pluto specific page called "Society of Unapologetic Pluto Huggers" welcome to join it.. Work closely w/the PI of the New Horizons mission.. Dr Alan Stern..
Any Pluto related help.. send me message.. Love your thread, so joined IceInSpace today.. not an imager..
Hope this all helps..
Raj Pillai
Last edited by Plutoholic; 18-06-2015 at 11:23 PM.
Thank you for the updates, and welcome to Ice In Space. I hope you have a good time here and enjoy the diverse crowd. Always something happening !
Are you involved with any astronomy groups in India ?
Yes Bruno's prediction has moved south, although I think to observe anyway. The current 1-sigma is around 400km for the RIO group, and about 1100km for the MIT group. So observations even 1000km north of Melbourne still have a reasonable chance.
As a aside, Andrew Cole might not actually want his email address publicised here. It might be good to confirm with him first before publishing it, to avoid him getting spammed.
News from the MIT crew - their prediction has moved north. Now Melbourne and perhaps as far north as Canberra is/are in the shadow. Previously their estimate was Launceston was at the northern extent of the shadow.
Tony,
Thanks for the input... How can one delete A.Cole's email ID.. though I got it from a simple Google search..
Want to know how many are imaging from Aus this event.. Interested in the Movie of the image.. not the light curves..
Thanks, Raj
