fourtwo

My attempt at timing the occultation of TYC 6394-00986-1 by (618) Elfriede
was met with the usual cloud. Those who read the posts in the forum will have seen that AJ and others did get a result. To date I have not seen a report posted on the RASNZ site to show the combined results of the observations.
My next excursion to attempt a timing of one of these events will be in July and a summary of the event by Steve Preston follows.

IOTA/IOTA-ES occultation update for
(2151) Hadwiger / HIP 61558 event on 2008 Jul 05, 09:36 UT
Visible from New Zealand, Australia

Summary
-------
On 2008 Jul 05 UT, the 20 km diameter asteroid (2151) Hadwiger will occult a 5.9
mag star in the constellation Virgo for observers along a path across New Zealand
and Australia.

In the case of an occultation, the combined light of the asteroid and the star
will drop by 10.3 mag to 16.2 mag (the magnitude of the asteroid) for at most
1.1 seconds.

This update is based on UNSO/Flagstaff astrometry for the asteroid kindly
provided by Alice Monet, historical astrometry from the MPC files (via AstDys),
and the following catalogs for the star position: .

The event at a glimpse
----------------------
* Rank: 32
* date and approx. time of event: 2008 Jul 05, 09:36 - 2008 Jul 05, 09:41 UT
* midpoint of event [JD]: 2454652.90014167
* magnitude of target star: 5.9
* magnitude drop [mag]: 10.3
* estimated maximum duration [s]: 1.1
* Moon: 7 % sunlit, 56° distance
* Sun: 87° distance
* rough path description: New Zealand, Australia

The occultation path
--------------------
* approximate projected width [km]: 20
* 1 sigma uncertainty interval [path widths]: +/- 2.07
* 1 sigma uncertainty interval [seconds]: +/- 2.4
* 1 sigma uncertainty interval approx RA,DE ["]: (+/- .023 +/- .024)
* 1 sigma uncertainty ellipse (major, minor, PA): ( .025", .023", 145° )
* approx speed of asteroid's shadow [km/s]: 18.6635
* website for maps:
http://www.asteroidoccultation.com

Data for the target star
------------------------
* name: HIP 61558
* constellation : Virgo
* J2000 position with proper motion to date of event [h,m,s ; °,',"]
RA: 12 36 47.3380 DE: -05 49 54.994
* position source: mpos:HIP pm:HIP plx:HIP
* standard error: RA,DE ["]: ( .011, .009 )
* V mag [mag]: 5.9
* B mag [mag]: 6.0
* Apparent position with proper motion
RA(deg): 189.3095306834 DE(deg): -5.8803126310
* Equation of equinoxes (radians) : 0.000051964384424
* remarks:

Data for the minor planet
-------------------------
* general information:
(number) name: (2151) Hadwiger
approx. diameter [km]: 20
approx. diameter ["]: .011
distance from Earth [AU]: 2.42300

* orbital information:
orbit source: Preston
date of fit: 2008 May 22
source of used astrometry: FASTT MPC (via Astdys)
number of used observations: 640
number of rejected observations: 27
time covered by the observations: 1934 Mar 07 - 2008 May 06
1 sigma uncertainty ellipse (major, minor, PA): 0.024, 0.020, 140°
remarks:

* orbital elements for (2151) Hadwiger :
Mean anomaly = 94.66127259 deg
Arg. of pericenter = 84.92645615 deg
Long. of node = 28.07903131 deg
Inclination = 15.46708268 deg
Eccentricity = 0.05713048
Semimajor axis = 2.56100708 AU
Perihelion dist = 2.41469552 AU
Mag: H = 10.87, G = 0.15
Epoch of elements : MJD 54652.40000000 TDT
(2008 Jul 05.400)

The prose and cons for travelling to time this event are: It is a resonable bright star at Mag 5.9, the altitude is good at about 50 Deg, and it will be in the WNW away from Brisbane lights, it is also nice and early at 19:39 local time. As Murphy dictates this is the day Cherrie arrives back from 6 weeks in Singapore. I don't think she will want to go anyplace as it is an overnight flight and she will be pretty stuffed.
I will most likely travel to a site near Gatton. It is a small dam called Lake Clarendon. This will put me in the shadow path for a northern chord. The shadow path is only 20Km so a minor shift will make a difference. This being so I will not make a final decision until any updates are posted on the net.

Below is a google earth image of the proposed site. This is an old image, I am sure that after the rain we have had over the last 6 months, some water will be in the dam.

Below is a map generated by Occult4 prediction software. I have modified it to show the times and PA's of the events as seen from Sydney, Melbourne, Bright and Adelaide. All times are UT. Sorry Rob, I did not put a dot in for you as it would crowd things a little. Your PA's are roughly halfway between Melbourn and Adelaide.
Little else is going on at the moment. All the predictions for Grazes and Asteroid events for the next month are just a little too far to travel to. I will be sticking to total Lunar occultations for a little while and will try to upload some of the reductions from those events here. This will give some of you an idea of the sort of things that I do with the information from the video recording.

I did not make the drive to western NSW for the Emanneia event as the weather was just too uncertain. It would have been a different matter if Cherrie was able to go as we could put in some birding to make the trip worth while.

There is an event with (1000) Piazzia on the 29th of April that is close to a birding area west of St George. We have visited this area before and like it. So if Cherri can make it then I will try for it.

An early check of weather sats gave me enough incentive to head north for this event, even though it was cloudy in Brisbane. It was an uneventful trip with enough sucker holes in the cloud to keep me optimistic. I had a good look around the roads SW of the highway between Howard and Torbanlea. I finally settled on a spot at 25deg 19' 55" south and 152deg 31'36" east. Not a great spot but good enough, on a back block gravel road.



The picture above is where I set up, looking ENE. This was taken at about 5:30 UTC. Soon after this picture the clouds began to break up from the north through east. There was a cool easterly breeze so I had a cup of coffee read the paper and fell asleep. A few spots of rain woke me at about 7:30 UTC. Seven hours to the event. What should I do?
I waited it out for a couple of hours more while I stuffed about with my Turbo Modem so I could check the weather sat pictures. Murphys Law in action. When I finally got a connection long enough to download a picture I saw a big mass of cloud pushing up from the south. I decided then to pack the gear (only the 'scope and mount were out at this point) and do a run out along the Isis Hwy to Dallarnil then loop up to Cordalba and back to Childers via the Bruce Hwy. This is an area known to me, where I had set up for grazes in the past.
Alas it was all the same picture throughout the region, so I turned for home.
A few good points came out of the exercise. I have proved the ability to set up and pack up quickly. From now on I will be testing everything the day before, including small electronic devices.
Now to get started on the next one.

Not a good start for Asteroid Occultations so far this year. Cloud and rain prevented observation of the (149) Medusa event in SE Queensland. I am not sure how things went further West. I do not know if there are any observers out there and there is no report on the RASNZ site at this time.
The next chance I get to record one of there events will be the (82) alkmene Occultation of HIP 59771 on the 20th of Jan at about 14:18 UT. The updated central path of this event passes through Childers and because I have a brother in law living in Bundaberg (with a boat) I will travel up that way to make the attempt (and may get some fishing done also).
There are a number of places off the Bruce Hwy between Maryborough and Bundaberg that I know will serve as a spot, but I will give myself plenty of time just in case I have to move on to someplace between Appletree Creek and Gin Gin.
My greatest enemy as usual will be the weather, especially the development of the present low in North Qld.
Other problems will be: The star is low in the ENE at about 30 degrees and I have not yet made a positive ID of it. The Moon will be high and bright, at about 97% sunlit. Apart from that the only other problem will be the travel time, but I enjoy the driving so that will not be too bad.



Above is a Google Earth image of the path near the area I am interested in. I hope I can follow up on this post with some pictures of a successful occultation.

I will not be able to update much here for the next few weeks because I am going overseas again for a little while. When I get back I will be putting up some pictures of the equipment and, I hope, a run down on a trip to capture the occultation of HIP 59771 by the asteroid 82 Alkmene.

Had a little time to day (15/12) so here is a picture of the equipment I use for the video capture and time stamp.

The type of equipment one uses for the timing of occultations will vary depending on what the observer wants to achieve. If the only requirement is to look at some of these events then all one needs is a telescope and some way of viewing predictions. Predictions of the brighter Lunar events are published in year books and give a time correct for a capital city. The observer can then do a little simple math to adjust the time for another location. That is if the observer's location is a long way from the predicted place, if it is within say 200km then it is probably not worth the effort, just give yourself plenty of time to spot the star. Another place to view predictions is on the web at the RANZ Occultation Section site http://occsec.wellington.net.nz/ . From this page one just follows the links on the left to total or grazing occultations. Another option is to download Occult v4, a progrmme that will provide you with predictions for any location you specify. A link to this programme can be found on the NZ site. Asteroidal events are a little different, because the shadow path is narrow an observer needs to be closer to the predicted path to see the event, but more about Asteroids later.
If an observer wishes to time the events then more equipment is required. One of the most important is an accurate, reliable, time base. With the demise of VNG this is harder to achieve than one may, at first, think. If you refer to the above website and follow the links to the timing page you will see what is available. It was this problem that prompted me to set up using a video and time inserter. I feel that this is by far the best way to get accurate timing results.
My requirements were for a portable telescope (ED100 on a HEQ5 mount), a video camera (GSTAR-EX), time base (Garmin 18 LVC) a video time inserter (KIWI-OSD) and a video capture card for the laptop. Once again there are links on the NZ website where you can view the sort of results achieved with this type of equipment.

First a little history to explain why I do this sort of thing. I first got interested in the timing of Solar System events back in the early 80's. My interest in astronomy, in those days, was mainly Solar System orientated. Bundaberg was my home town at the time and I was a member of the Bundaberg Astronomical Society. As a member of BAS I was asked to head up the Current Phenomena Section of the society. This prompted me into researching such things as Lunar total and grazing occultations, Jovian Satellite Phenomena and Meteor events.
I joined a number of organizations including the Internation Occultation Timing Association (IOTA). IOTA sent me total and grazing occultation predictions on a regular basis, and I returned report forms to them. In those days this was all done by snail mail. I organized a few members of BAS to travel to graze locations on a few occasions. I had a great time doing this as it incorporated another interest of mine, mapping. I would plot the profiles of the grazes on a map and then recce the places that telescopes could be set up. I was able to do this as I regularly drove the area in a delivery van.
Timing of the events in those days was easy as VNG was transmitting a time signal code on a number of shortwave frequencies. I was able to mix the radio beeps with my voice onto a tape recorder. When played back I was able to etimate the event time to a few tenths of a second.
All this came to an end in 1990 when I moved to Macky.
Now I am in Brisbane and the old bug is back. I spent a long time trying to sort out the best way to get back into event timing. With VNG gone and the WWVH time signal being, at the best, unreliable I decided to bite the bullet and purchase the gear to set me up to video and time stamp the events. AJ, another SCP, member purchased this gear just befor me and it was his thread that prompted me to go ahead and get set up.
Soooooo, now to timing.