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Old 21-10-2009, 11:05 PM
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Screwdriverone (Chris)
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My First Occultation - and contribution to Science

Hi Everyone,

Just thought I would share a little (well, it's not so little) story about something that happened tonight that I got quite a kick out of...

I went to our monthly meeting at the UWS Nepean Campus for the Western Sydney Amateur Astronomy Group (WSAAG) where we met and discussed club matters etc. After the formalities we had a presentation on Occultations by Dave Gault and he also gave us a quick run down on his new toy, an Ioptron Cube on which he has mounted a 5 inch SCT.

Now, I had heard of occultations and read about interesting events in AS&T and here on IIS, but some of the observations and data that Dave collects were intriguing and thought provoking as to how much we amateurs can observe and contribute by observing such phenomena.

We heard of how Dave is contributing to a massive database of ongoing occulation observations and how there are planned events coming up to observe occultations of stars behind the edge of the moon and how this data can be used to measure the heights and troughs of the mountains on the limb of the moon!

By using observers on baselines of up to a KILOMETRE or more, Dave organises observations that are synchronised against "beeper boxes" and timed with the disappearance and reappearance of bright stars grazing the moon's limb. By lining up groups of people with scopes along a line at varying distances anywhere from as close as 50m to 200m apart, the time of the "blinking" on and off varies along the line and is recorded by each observer into a mobile phone on record mode with the beeper box in the background. By using code words of "GONE" and "BACK" these recordings are all then collected and referenced against the UT of the event and the individuals time and then collated into a database of observations. The different times of the occulted star can be referenced along the baseline and this can then work out, based on the distances between the observers (and I assume with trigonometry) the measurements of the mountains on the moon. I thought all of this sounded PRETTY COOL!

Now I assume this is all riveting reading for you, but, stay with me, I will come to the point....

After the meeting, or more accurately, because the sky was clear at the time, we wrapped up early and wheeled out the 16 inch Dob and Dave's Cube as well as other members set up their Dobs to try and observe an Occultation event at 2100 AEST or thereabouts where the moon was to occult a star in Scorpius (not sure of which one, but I am sure someone will supply it for me).

With the moon only 11% illuminated, the 8th magnitude star was to "approach" the dark limb of the moon's face and then "blink" off as the moon passed in front of it. We had the scopes lined up and looking and could see the moon getting closer and closer as the event neared. Dave then brought out his "beeper box" which had already been synchronised to UT beforehand and asked if anyone wanted to do the observation. Well, after being intrigued about the "science" of this subject I jumped at the chance!

I offered to sit at the 16 inch dob and perform the observation and after realising my crappy Nokia that I had with me couldnt voice record (left the stinking Blackberry Bold at home - ) Dave gave me his mobile and set it to record with the instruction to call out "GONE" when the star disappeared.

Now the beeper box is just how it sounds - it is synchronised to UT accurately by computer (or even via the internet or GPS in the field - pretty cool) and provides a steady second beep with higher pitched beeps when it approaches a minute tick over and then goes silent. [these are apparently made by a very clever lady in NZ who makes them, solders them all up and puts them in a jiffy box]

Well, the time approached and I was glued to the eyepiece, watching the moon approach the small star, closer, closer, closer.... I was starting to actually get nervous as I thought I might blink and miss the event. There was chatter coming from our members all outside enjoying the night and the company and having conversations about this and that. It was getting quite exciting. Then, faster than you know it, the star "hung" for a split second and disappeared. Well, without thinking, I called out "GONE" and the mood all changed. Dave piped up to confirm and then the other members I think were a bit shocked that something happened so abruptly after waiting for a while and were discussing other topics. I must admit, for the first time I had seen it happen myself, it was quite a rush at the time...lots of fun in fact!

Now, my understanding of the "science" of it all is that when you call out "GONE", that moment is recorded on the phone and is determined by analysing the recording to be the exact time by referencing where the beeps are in their pattern and also with the local time of the event, which then allows Dave to record an observation (I assume also by referencing the lat/long location of where the observation happened) which then allows an accurate report to be generated and submitted to the International Occulation database. This apparently (which I learnt tonight) has been going since 1629!!!

The thing that got me all proud of myself is that Dave recorded my name as the person who did the observation so he can submit it and this made me feel all special-like and sort of important because little old me had contributed to an observation!

One small observation for an amateur Astronomer, one really cool and fun thing to do on a Wednesday night for astronomy science!

I hope you enjoyed my "report", Dave joked that I have now crossed over to the "dark side" and there is no turning back now....

Oh dear, NOT AGAIN!

Thanks for reading and cheers for now,

Chris
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Old 21-10-2009, 11:17 PM
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jjjnettie (Jeanette)
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How many dark sides are there to this hobby of ours?

Great report Chris. To be able to contribute to science, even in this small way is an achievement to be proud of.
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Old 21-10-2009, 11:21 PM
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Screwdriverone (Chris)
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Thanks Jeanette,

I am pretty proud of myself, as you can probably tell, a lot of fun too!

Oh look, 1100 posts, another achievement, only 2 more for you to get 7000!

2 more dark sides?

Cheers

Chris
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Old 21-10-2009, 11:47 PM
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Thought that was fun ... well try this!

Hi Chris,

Quote:
Originally Posted by Screwdriverone View Post
Well, after being intrigued about the "science" of this subject I jumped at the chance!


Well, the time approached and I was glued to the eyepiece, watching the moon approach the small star, closer, closer, closer.... I was starting to actually get nervous as I thought I might blink and miss the event. There was chatter coming from our members all outside enjoying the night and the company and having conversations about this and that. It was getting quite exciting. Then, faster than you know it, the star "hung" for a split second and disappeared. Well, without thinking, I called out "GONE" and the mood all changed. Dave piped up to confirm and then the other members I think were a bit shocked that something happened so abruptly after waiting for a while and were discussing other topics. I must admit, for the first time I had seen it happen myself, it was quite a rush at the time...lots of fun in fact!

Now, my understanding of the "science" of it all is that when you call out "GONE", that moment is recorded on the phone and is determined by analysing the recording to be the exact time by referencing where the beeps are in their pattern and also with the local time of the event, which then allows Dave to record an observation (I assume also by referencing the lat/long location of where the observation happened) which then allows an accurate report to be generated and submitted to the International Occulation database. This apparently (which I learnt tonight) has been going since 1629!!!

The thing that got me all proud of myself is that Dave recorded my name as the person who did the observation so he can submit it and this made me feel all special-like and sort of important because little old me had contributed to an observation!

One small observation for an amateur Astronomer, one really cool and fun thing to do on a Wednesday night for astronomy science!

I hope you enjoyed my "report", Dave joked that I have now crossed over to the "dark side" and there is no turning back now....

Oh dear, NOT AGAIN!

Thanks for reading and cheers for now,

Chris
Well done Chris ... and if you enjoyed that, wait till you get involved in a graze expedition (ask Dave) and I'm sure he'll organise to include you on one.

Instead of seeing just one occultation, you might see as many as three or four in a minute -- all on the one star as it grazes along the lunar limb. Even more valuable as science so long as several observers are involved.

I went on a dozen or so graze expeditions as a youngster. They were quite a craze in the mid to late 70s at the Sutherland Society. I think the most memorable/spectacular was a 2am one near Cooma when the Moon grazed Regulus. Not sure but I think it was maybe November/December 1979 ...?

Then there was the one I observed mid-winter (1978??) at Albion Park. My station was ... in the cemetery of a church. There were about 5 of us SASI people and maybe as many again from Illawarra observing it.

Great fun. Great memories.

And BTW ... congrats on 7000 jjj!


Best,

Les D

Last edited by ngcles; 22-10-2009 at 11:00 AM.
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Old 23-10-2009, 03:25 PM
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Screwdriverone (Chris)
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Hi Les,

Yes, Dave's talk was actually about the upcoming "graze" event and has it planned to do this around the Richmond area and observe this event with a LARGE baseline of people/scopes at the same time. I am tempted to go along and contribute as its not too far away from me and quite intriguing.

The interest is strong in this one ....

Cheers

Chris
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Old 23-10-2009, 03:44 PM
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What it looks like ...

Hi Chris & All,

This is what a graze of a 1st magnitude star looks like:

http://www.iota-es.de/regulus_2007/Regulus_graze.avi

just to whet your appetite ...


Best,

Les D
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Old 23-10-2009, 06:17 PM
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seeker372011 (Narayan)
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Chris
Dave has plenty of videos of his observations on U tube..and why not come along Sunday night if the weather is good?
its a even bigger buzz when the star reappears after blinking out-which is why a graze is so cool
Narayan
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Old 23-10-2009, 07:20 PM
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Excellent Chris - great report.

Cheers Petra d.
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Old 23-10-2009, 07:25 PM
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Chris,
Well detailed and interesting report! An example of the invaluable contributions by amateurs to astronomy whether it be occultations, variable stars observations, supernova discoveries or otherwise.

Regards, Rob.
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