It is not often that we have 3 high quality asteroid predictions that are observable from the Australia in the one month.The predictions for June 2015 have 3 such events, the first time that I can remember.
First off, let us define what is a high quality asteroid prediction, and in no particular order the attributes are;
- Reasonably bright star – a star brighter than mag. 12 is considered helpful.
- Asteroid fainter than star – it always helps to have the asteroid fainter than the star because then the magnitude drop when the even occurs is large, and this makes the event easier to see. In the case of the three events, all have mag.-drop of 2 or more.
- Event duration grater than 2 seconds – this helps to distinguish atmospheric scintillation from a real event.
- Error in time less than 5 seconds – this helps because we know with certainty that the event will occur at a certain time and we don’t have to watch the star for minutes at a time.
- IOTA Rank greater than 90 – IOTA ranks all event on a scale up to 100, where an event of 100 means that if an observer is sited between the bold path lines shown on the map, then they almost certainly will see the event.
- The event has extremely high value because the data obtained from the observations will directly aid space exploration. The 29th June Pluto event falls into this category.More on this later.
Lets discuss the events in detail. (refer to the Occult prediction maps).
5th June : (212) Medea occults TYC 0604-1157
This event occurs at 19:04:22 UT = 5:04:22 am on Saturday morning. The star is mag. 11 and the asteroid is mag. 14, so the mag.-drop is 3.1, making this easy for visual observers.
The southern limit crosses Sydney CBD, so any sites to the north-west, like Linden Observatory will benefit with greater event certainty.
The star and asteroid will be at alt. of 32° and az. of 52° at event time.
Steve Preston (of IOTA) has sourced the star position from the URAT1 catalogue, so we can be assured that the star position coordinates are the best available.
19th June : (420) Berthholda occults TYC 628-01716
This event occurs at 14:33:57 UT
= 12:33:57 am on Saturday morning. The star is mag. 11.6 and the asteroid is mag. 13.4, so the mag. drop is 2.0, and it is still in the realm of the visual observer.
The path is centred on Sutherland, and extends from Gosford to Moss Vale, so anywhere between those limits will see the event.
The star and asteroid will be at alt. of 74° and az. of 14° at event time.
Steve Preston (of IOTA) has sourced the star position from the URAT1 catalogue, so we can be assured that the star position coordinates are the best available.
29th June : Pluto Occults 4 UCAC 347-165728
This event occurs at 16:48:40 UT
= 2:48:40 am on Tuesday morning. The star is mag. 12 and the Dwarf planet is mag. 14, so the mag. drop is 2.2, and it is still in the realm of the visual observer, however the disappearance and reappearance events will be gradual, taking many seconds to occur, due to Pluto’s atmosphere.
The predicted path, obtained using the UCAC4 catalogue and the Pluto DE432 ephemeris, covers almost all of Australia, however we expect updates from The RIO Group (Felipe Braga Ribas et al) leading up to the event.The RIO Group perform precise astronomy on the target star and Pluto and produce high quality predictions.
Any positive observations from this event could benefit the New Horizons flyby.
Marc Buie of The Southwest Research Institute writes; It's (the occultation) going to be a very important with its occurrence so close to the New Horizons flyby and it's own occultation experiments. It's also nice that the star is bright (and red).
One goal for this event will be to go for extra density coverage on the central flash if that part of the shadow is accessible over land.
This prediction work, when completed, will be distributed to everyone with any interest in this event. I expect Bruno and Felipe will be crucial to getting the word out.
I wish I could be in the field with everyone to observe this for myself but I'll be tied up in Baltimore with all the activities surrounding the New Horizons encounter with Pluto. I'm on the hazard team that is on the lookout for dangerous stuff on the way in. It's going to be a crazy-busy but exciting time.
--Marc
So I encourage all observers to monitor these three events. I have indicated that all three events are observable visually (with telescopes 8” or larger) but if you do have time inserted video technology, use this in preference.Should you require advice on how to go about this, please contact me at; dave4gee (AT) yahoo.com.au
Should you observe a positive event, please contact me and I will direct you to the proper reporting person and their email address.
I'll let Dave know. It's not in my OW feed either.
EDIT:- Dave has some Internet Service Provider issues. He can't upload new stuff right now. I think he's not that happy about it, but has no way to connect.
Regards
Tony Barry
Last edited by tonybarry; 21-05-2015 at 07:57 PM.
Reason: added info.
As for Pluto - the timing of the event is almost irrelevant for two reasons. Firstly, we can retro-fit the event based on other timed observations and secondly, the scientific payload is observing differences in the shape of the curve in the centre (the central flash) at different wavelengths to give an indication of atmospheric shape and zonal winds. The Horizons project won't be doing this, so its up to us!!!
So it is critical to get a video of it for it to have scientific value. If anyone with a video device such as a gstar, imaging-source, or ZWO120 can make a really useful contribution simply by making a recording of it and letting us have a copy...
As for Pluto - the timing of the event is almost irrelevant for two reasons. Firstly, we can retro-fit the event based on other timed observations and secondly, the scientific payload is observing differences in the shape of the curve in the centre (the central flash) at different wavelengths to give an indication of atmospheric shape and zonal winds. The Horizons project won't be doing this, so its up to us!!!
So it is critical to get a video of it for it to have scientific value. If anyone with a video device such as a gstar, imaging-source, or ZWO120 can make a really useful contribution simply by making a recording of it and letting us have a copy...
just confirming that the Pluto event won't be visible from Melbourne?
One from IOTA, using UCAC4 positions and DE432 offsets, predicts a shadow from about Darwin to about Port Pirie. (Melbourne is too far south).
Another from the RIO team, using UCAC4 positions, DE413 offsets (which are older than DE432), but with astrometric observations of the target star, predicts from Rockhampton to Auckland. (Includes Melbourne).
A third from the MIT crew, predicts from Melbourne to Antarctica. Melbourne is the northernmost point where the occultation can be seen.
Pluto is around 40AU distant, light takes 4.5 hours to reach here, and an error of 20 milli-arc-seconds in star position will easily cause the variations we see in these predictions.
Moral of the story - observe first, debate later.
My earnest advice to anybody who wants to see a rare bright occultation of Pluto, see the atmosphere effect of Pluto, and perhaps even help out with the New Horizons mission ... observe this occultation. The last mag.12 occultation of Pluto was six years ago.
One from IOTA, using UCAC4 positions and DE432 offsets, predicts a shadow from about Darwin to about Port Pirie. (Melbourne is too far south).
Another from the RIO team, using UCAC4 positions, DE413 offsets (which are older than DE432), but with astrometric observations of the target star, predicts from Rockhampton to Auckland. (Includes Melbourne).
A third from the MIT crew, predicts from Melbourne to Antarctica. Melbourne is the northernmost point where the occultation can be seen.
Pluto is around 40AU distant, light takes 4.5 hours to reach here, and an error of 20 milli-arc-seconds in star position will easily cause the variations we see in these predictions.
Moral of the story - observe first, debate later.
My earnest advice to anybody who wants to see a rare bright occultation of Pluto, see the atmosphere effect of Pluto, and perhaps even help out with the New Horizons mission ... observe this occultation. The last mag.12 occultation of Pluto was six years ago.
Regards,
Tony Barry
WSAAG
Yes thanks for that Tony, I thought I had seen that there were a few differing views on the location a while back (with one including Melbourne), but hadn't heard anything for some time, I wasn't sure if the predictions had been further narrowed down to be outside of Melbourne. I am thinking I may have a crack at it, I wonder if the A7s will be capable in video mode, or perhaps I can hook up the lodestar somehow for recording.
I wonder if the A7s will be capable in video mode, or perhaps I can hook up the lodestar somehow for recording.
I'd love to know too. I have my eye on that fabulous camera!
Of course, you can test it between now and then - just find a 14th mag star and set the iso so that you can see it clearly with a low exposure - Our cameras will be something around .25 to .5 second exposure for 14th mag.
The star that will be occulted is much brighter at mag 12, but we are looking to get a good result at the minimum brightness (14.2)
Its a balancing act between amplification and exposure, so it would be great if you could post some frames here so we can see what your set up is capable of - Its my guess that it could be fantastic!
The Sony A7s has a good reputation for low light, low noise imaging.
You would need to test it out on the star in question, with your chosen scope, to see how it would go as a movie mode device. That would be an easy first step, and something you would do anyway to get a good experience with the field of view and the behaviour of your camera.
Traditional occultation recordings have precise timekeeping as a major input to the science. As Jonathan says (above) the central flash is the big money for the science crew, but good timekeeping will still be very important. For example, if you are close to (but not right on) the central line, your central flash recording will display a different behaviour to a dead centre line. Now if the field of observers is densely packed and we get a lot of chords, then yes we may be able to retrofit your chord to the rest of the pack based on your location. This is not ideal, but desperate people can do desperate things :-). Also bear in mind that Pluto has an atmosphere, and the soggy ingress and egress light curves do nothing to make that retrofit alignment task easier.
If the field is not packed and we have few chords, then timekeeping, preferably to the millisecond and referred to UTC, is really quite necessary. At the very least, syncing the camera with the computer clock will get you to within a second if the computer is running Network Time Protocol and it is properly peered to a local server. But be aware that NTP has to be running, and working, and for that something like Dimension4 or TARDIS, and a good ADSL link, might be helpful.
Most of the regular occ people who correspond here use GPS based video time insertion of one flavour or another, and analog video cameras.
I am currently reading Bruno Sicardy's paper on the central flash of an occ of Neptune in 1998:-
which is a bit to get through but I am getting to appreciate the science behind the observing of the central flash, and in particular what observers (such as us) might want to do to prepare properly for the event.
Again, I would encourage you to observe the Pluto event. It is probably a once-in-a-decade occultation for brightness, and a once-in-a-lifetime chance to help out with a NASA space probe data collection.
I've got an old KIWI-OSD I could lend you Russell, but it needs to be "rebooted" because it hasn't been used in so long (something I will need to ask other occ section members about, but I think I've seen someone else do it). I'm planning on coming along to the MPAS members night on Sat, might see you there? Could always drop it off another time, too, if you're keen.
I'd love to know too. I have my eye on that fabulous camera!
Of course, you can test it between now and then - just find a 14th mag star and set the iso so that you can see it clearly with a low exposure - Our cameras will be something around .25 to .5 second exposure for 14th mag.
The star that will be occulted is much brighter at mag 12, but we are looking to get a good result at the minimum brightness (14.2)
Its a balancing act between amplification and exposure, so it would be great if you could post some frames here so we can see what your set up is capable of - Its my guess that it could be fantastic!
that's a good idea, next time I set up i'll do some investigating.
Quote:
Originally Posted by tonybarry
Hi Russell,
The Sony A7s has a good reputation for low light, low noise imaging.
You would need to test it out on the star in question, with your chosen scope, to see how it would go as a movie mode device. That would be an easy first step, and something you would do anyway to get a good experience with the field of view and the behaviour of your camera.
Traditional occultation recordings have precise timekeeping as a major input to the science. As Jonathan says (above) the central flash is the big money for the science crew, but good timekeeping will still be very important. For example, if you are close to (but not right on) the central line, your central flash recording will display a different behaviour to a dead centre line. Now if the field of observers is densely packed and we get a lot of chords, then yes we may be able to retrofit your chord to the rest of the pack based on your location. This is not ideal, but desperate people can do desperate things :-). Also bear in mind that Pluto has an atmosphere, and the soggy ingress and egress light curves do nothing to make that retrofit alignment task easier.
If the field is not packed and we have few chords, then timekeeping, preferably to the millisecond and referred to UTC, is really quite necessary. At the very least, syncing the camera with the computer clock will get you to within a second if the computer is running Network Time Protocol and it is properly peered to a local server. But be aware that NTP has to be running, and working, and for that something like Dimension4 or TARDIS, and a good ADSL link, might be helpful.
Most of the regular occ people who correspond here use GPS based video time insertion of one flavour or another, and analog video cameras.
I am currently reading Bruno Sicardy's paper on the central flash of an occ of Neptune in 1998:-
which is a bit to get through but I am getting to appreciate the science behind the observing of the central flash, and in particular what observers (such as us) might want to do to prepare properly for the event.
Again, I would encourage you to observe the Pluto event. It is probably a once-in-a-decade occultation for brightness, and a once-in-a-lifetime chance to help out with a NASA space probe data collection.
Regards,
Tony Barry
WSAAG
Hi Tony, thanks for the indepth replies. I maybe just outside Canberra also, but its fascinating that there can be such differing predictions. Is there any particular reason you follow the prediction for the north of Melbourne?
Unfortunately my laptop is fairly terrible and just runs PHD2 and BYEOS, while attempting to obtain video in Backyard eos the fps was very low probably around 8-10. I know the A7s has a gps in it i'm not sure how accurate it would be and useful in the exif data in addition it also has timecode although I don't know much about that either (perhaps it could be linked to the KIWI OSD).
First things first I need to check the video capability out.
Quote:
Originally Posted by Blue Skies
I've got an old KIWI-OSD I could lend you Russell, but it needs to be "rebooted" because it hasn't been used in so long (something I will need to ask other occ section members about, but I think I've seen someone else do it). I'm planning on coming along to the MPAS members night on Sat, might see you there? Could always drop it off another time, too, if you're keen.
Thanks for this, unfortunately I rarely make the MPAS meetings due to being so busy! I am not familiar with the KIWI-OSD does it include a camera or do I plug one into it then use through a laptop? Potentially I could have the A7s going on the 12"f4 and another camera on my dob 12"f5 (lodestar?)... I've got a bit of reading to do!
I am not familiar with the KIWI-OSD does it include a camera or do I plug one into it then use through a laptop? Potentially I could have the A7s going on the 12"f4 and another camera on my dob 12"f5 (lodestar?)... I've got a bit of reading to do!
No, its just the video time inserter (VTI). You need to have telescope=>video=>VTI=>recorder in sequence. The video goes into the VTI, gets the time stamp inserted onto the frames, then comes back out and on to whatever you are recording on.
