Asteroid Zelinda Occultation - 10 Sept 2007

Hey Vagelis, really nice work!

This is something on my to do list and a goal well worth pursuing, not only for useful scientific purposes which can be shared but also as a matter of personal achievement. I have a Watec 902DM2S ½” CCD video camera fitted onto an 8” SCT with F6.3 FR.
I have software that will automatically time stamp (and other data) onto video frames, while timing is by means of “Atom Time Pro”.
Did you manage to complete any photometric measurements from your video?

Clear skies
Mike

Just some information for those that wish to video record a star occultation by an asteroid event from Ireland for this, the month of March (2008). I’ll give it a go if clear; the times for these events are sociable.

Minor Planet “3273 Drukar”, 7th march 22:53>23:02 UT
astrosurf.com/eaon/Cartes/03%20March/07_drukar.htm (from south east to south west Ireland looks prime location for this event).

Minor planet “6924 Fukui”, 14th march 20:47>21:07 UT
astrosurf.com/eaon/Cartes/03%20March/14_fukui.htm (south east to northwest Ireland).

Minor planet “4350 Shibecha”, 22nd march 21:50>22:03 UT
astrosurf.com/eaon/Cartes/03%20March/22_shibecha.htm (approx. Dublin - Galway track).


Clear skies
Mike
astrosurf.com/eaon/Occultations%20March.htm

Hey Vagelis, really nice work!

This is something on my to do list and a goal well worth pursuing, not only for useful scientific purposes which can be shared but also as a matter of personal achievement. I have a Watec 902DM2S ½” CCD video camera fitted onto an 8” SCT with F6.3 FR.
I have software that will automatically time stamp (and other data) onto video frames, while timing is by means of “Atom Time Pro”.
Did you manage to complete any photometric measurements from your video?

Clear skies
Mike

Hi Mike,
Zelinda was a clear case, no photometry needed, because the star is clearly visible at frame 20:51:21.112 UT and disappears at frame 20:51:21.152 UT and then reappears at frame 20:51:31.352 UT.
We do photometry whenever the magnitude drop is considerably small, or the recording is uncertain.
The best program for occultation photometry is Limovie: www005.upp.so-net.ne.jp/k_miyash/occ02/l...928/limovie0928.html

Are you going to try any of these events in March?

I wish you all the good luck,
& Clear Skies!

Just some information for those that wish to video record a star occultation by an asteroid event from Ireland for this, the month of March (2008). I’ll give it a go if clear; the times for these events are sociable.

Mike, have you ever tried an occultation before, or is it your first time?

Hi Vagelis
Many thanks for the information and of course advice. I haven’t tried imaging an occultation of a star by an asteroid yet, but it is definitely something I would like to attempt. This month maybe my chance (and others) weather permitting of course.

I’ve downloaded LiMovie and have been trying it out with random star fields I recorded just to practice, there is a technique in RegiStax I am sure you are aware of for pre-registration and enhancement of video frames which can then be read by LiMovie very precisely and produce a light curve. I was wondering if you use a more sophisticated analysis program such as Mira Pro, would it be possible to ascertain if a shape profile of the asteroid maybe forthcoming as well if the conditions were right. Worth a try I suppose!

Clear skies
Mike

Hi Mike,
You have a good camera, which is ideal for occultation (or meteor) work!
It is very good news that you are going to try occultations, so I would like to give you some more advise!

1. These particular events in March for Ireland that you have spoted, are all low probability - high uncertainty events. So you must be prepared not only for positive, but also for negative observations.
eg, for Fukui, on the prediction map, if you look at the "Center line %", "Shadow edges %" and "1-sigma lines %" you can see that the numbers are 7%, 7% and 4% respectively, which is, really, very low probability. For comparison see astrosurf.com/eaon/Cartes/02%20February/05_aspasia.htm where the numbers were: 98%, 50% and 16%, and most observations were positive www.euraster.net/results/2008/index.html#0205-409 - Aspasia was a sitting duck. But such cases are not very often (I mean, to happen often at any particular site).

I am not saying you should not try these events, to the contrary, occultations is a non-stopping chase, and success is for those who dare and go against the odds.
Secondly, not only a positive, but also a negative report has scientific value. It is valuable information if an observer reports that he observed NO OCCULTATION from a SPECIFIC site (precise long and lat) at a CERTAIN time UT. The scientists will take it from there and will do their job in the model of the asteroid orbit in relation to the prediction data used.
Personally, I observed my first occultation while I was, against all odds, near the 1-sigma line. And then I thought: "Well, now I know why I missed at my last 12 attempts: I was placed at the center line!!" he he.

2. DO locate the star to be occulted and its surrounding field of view at least 1-2 nights before the occultation night. You will have a lot to do during those last couple of hours before the predicted time. Strugling to find the star at the last moment is out of question. Ideally, you should have located it early enough.

3. Be prepared to report precise latitude and longitude of the observing site, as well as UT time.

4. Read the bible: “Chasing the Shadow” The IOTA Occultation Observer’s Manual www.poyntsource.com/IOTAmanual/

5. It may sound strange as an advise, since you have this great Watec, but consider doing visual observations also. I am saying that because it is very inportant to understand what's the whole thing about occultations: TIMMING them!
Also take a look at EAON Circular 5: "The timing of visual observations" astrosurf.com/eaon/Circulaires/Circulaire5.htm Old stuff but you get an idea of the old methods and you can appreciate the technology advances of today.

6. Limovie and photometry can wait. It is the next stage, after you will have gained some experience. Your priority now should be clear events and how to precisely time them.
(I have used Limovie only in 2 cases, where there was no obvious star magnitude drop, and the results were also negative).

Clear Skies,
Vagelis.