SEQ: Naked eye asteroidal occultation 10 Oct

[AstroJunk]

It is outstandingly rare to have an oportunity to see a naked eye asteroidal occultation. Someone between Brisbane and Gympie may get lucky and spot the asteroid (3995) Sakaino blot out Theta Ceti (mag 3.6) for upto 1.4 seconds. Short but very sweet.

The event will happen on Saturday the 10th of Oct at about 7:55 pm. Theta Ceti will be 30 degrees high almost due East.

Please put it in your 'to do' list, it would be a really significant observation as this asteroid has never been measured before.

I will bang the drum a little closer too :thumbsup:

http://www.asteroidoccultation.com/2009_10/1010_3995_18539.htm

[coldspace]

Hi Jonathan,

Will this make for a good target to video record, I might give it a go if it is.
Also I might be just outside the target zone as I am in Shailer Park near the Hyperdome, still would it be worth having ago or are the calculations for the target zone accurate?

And if so will say .25 second intergrations be ok or would you need faster ones?

Matt.

[AstroJunk]

Matt, Asteroidal Occultations are a bit of a lottery. In this case that star position is very well established, but not the asteroid so it is absolutely worth recording - you will go down in history if you capture it!

If you are using your malincam, you can do this one live with no issues. Have a go before hand (once this dust clears)!

[jjjnettie]

I'll have to dust off the gstar for this one.
Thanks for the heads up Jon.

[coldspace]

Yep, bloody dust.
I will give it a try and pray for a lottery win.
Everyone with a means to capture something like this let me say the excitement if you pull it off is amazing, I have been part of a S/nova discovery and the rush that goes on when you pull it off is very rewarding, so I will be giving this one ago weather dependent.

Matt.

[pirate of skies]

Hey Matt,
Are you planning on using a scope for this, or naked eye ???
What size scope ?
I live at Tanah Merah, 2 minutes from you with an eight inch. I assume you get as much light pollution as me?
Visiting the website given by Astrojunk, it seems the Moon will be at 78 degrees and at 61%, so there may be a complete washout to see Theta Ceti naked eye. Will have to use a scope.

Just a heads up.

[AstroJunk]

Hi Rob, I wouldn't worry - that page is a little misleading. It is true that the moon is separated by 78 degrees from the star, but what it fails to mention is that it won't be above the horizon for another 4 hours :)

Clouds/dust/streetlights are going to be the main concern...

[coldspace]

I will be using a scope for this Rob unless its raining.
Its a 12 inch LX200R with a Mallincam astro video system attached so I won't have too much trouble seeing Theta Ceti. My combo can go down to about Mag 20 in 56 seconds on a good night here in the burbs but I won't be using long intergrations just short ones probally 0.15 seconds so if the star blocks out for the 2 seconds hopefully I can catch it, like Jonathan says, it will be a lottery win to capture but might as well have ago.

This sort of astronomy along with super nova searching which a good friend of mine does is what astronomy is all about and not just pretty pictures. I find it very interesting as its real action taking place out there.

Good luck with your observations.

Matt.

[jjjnettie]

Thanks Matt, I didn't think about integration times with this. Ta for the reminder.
Cheers

[coldspace]

At Mag 3.6 jjj, your g-star will be able to easily pick it up with very short intergrations, say 12X or even with the intergration setting off. Those g-stars are very sensitive.
The short intergrations will act like live viewing so if the star blocks out should be very cool.
I am going to try a few different intergration settings on the star this week to see what shows its nice and clear, if this dust ever goes.
I am going to record to a hard disk video recorder as I find this records the best live image then frames can be accessed from there. I am going to start recording 10mins before.

I've never down this before so should be fun, and if its blocks out what a prize.

Regards Matt.

[jjjnettie]

I'm looking forward to it too.

[citivolus]

I've listed myself as intending to observe this one, as my GPS timing software is coming together well enough that I think it will be running in time. Even though I am just outside the 1-sigma line, it is still worth having a go since the error margin is fairly high.

If all goes well the equipment would be ready for the magnitude 13 event with 554 Peraga just under 2 hours later. Admittedly the second one would be a bit more of a stretch for my equipment :)

[jjjnettie]

Which scope would be best? Seeing how it's such a bright occulation, could I get away with using the 80mm or is it still a case of aperture rules?

[[1ponders]]

Jonathan, what would be the easiest way to set up for the timing of this event? Can i use my laptop clock if I do a syn with tick.usno.navy.mil just before time and then run an AVI during the process. If the start time is known and the frame rate is known then the rest, as they say should be history. :)

BTW I'm about center of the very bottom of the 'b' in Nambour in your map.

the Kilcoy contingent look like they are going to get to nail it. :thumbsup:

[jjjnettie]

I can use the time stamp in the Gstar Capture, but how do you get your lappy showing the correct time?

[[1ponders]]

Double click on the time in the task bar. Select internet time. I use tick.usno.navy.mil as my syn and then click update and then apply.

[jjjnettie]

You're a champ, thanks.

[[1ponders]]

NP. I try to get into the habit of updating everytime I setup for some imaging. I may not need it, but you never know what may appear in an image. I wonder if there is a way to automatically update the 20D clock when I connect it to the laptop via USB. good question to start a new thread with. :cool2:

[citivolus]

I'm relatively new to this, however I have a few answers for you :)

If you have any dropped frames they will skew the perceived time, also this would give you second level accuracy at best. I'm currently working on a capture application to timestamp AVI frames as they are recorded using time from GPS and NTP sources, for exactly this purpose. It currently supports primarily the Imaging Source cameras. Basically I am hoping to provide an alternative to the Kiwi-OSD for people using USB/Firewire cameras. In the long term the app will need to be non-free, as I am needing to pay for the API, but I will be providing it for free to any willing beta testers :) I'm hoping to provide both lite and feature rich versions to keep the cost down for users who just need the basic features. Obviously any work/support/etc related to this will be kept off of IIS, as it is my own personal venture.

If you have a stable NTP server running on your laptop, and have adequate time for the clock to stabilise prior to your capture, NTP can be a viable clock option. The port of NTPD to Windows can be found here (http://www.meinberg.de/english/sw/ntp.htm). It will provide significantly better clock synchronisation than the bare bones SNTP implementation in Windows, as it actually attempts to discipline the system clock and not just periodically skew it.

However, as NTP requires a significant time to discipline a system clock, especially under Windows, I have additionally added support for directly reading a PPS and NMEA signal from a serial attached GPS receiver. The timing loop driven by this is capable of sub-millisecond accuracy, within tens of seconds of the GPS receiver acquiring a satellite lock, rather than the minutes to hours needed by NTP. GPS receiver hardware needed to support this is a Garmin 18x LVC in a serial configuration, as described and available here (http://psn.quake.net/gps/gps18.html), or a similar PPS capable serial GPS receiver with the PPS signal connected to the DCD pin. A unit in this configuration is around $100 AU if ordered from overseas, which isn't too bad considering what it provides.

Regards,
Eric

[[1ponders]]

Cheers Eric. I got the first line and the next paragraph, but the rest went over my head like a circus tent.:) However I would be interested in beta testing as I have DMK and DBK cameras (usb). Can you tone the rest down for me. What do I need in way of a GPS? I see the Garmin is serial, what about USB connection to a GPS?

[citivolus]

Hi Paul.

Basically the way that windows sets its clock when you use the Internet time sync option is that it periodically polls a time server and steps the system clock to match the time that it was told that it is. This results in discontinuities in the time, or the same time occurring twice, etc.

The better way to control the clock is to adjust the actual clock rate, so that the clock is running at the proper speed in the first place. This is the method used by NTPD, however it can take a fair amount of time to do clock adjustments using this method. In some systems, such as my laptop, the system clock is bad enough that NTP can never establish a steady state and NTPD can be a lost cause. This will happen whenever the system clock rate is off by over 0.5%, or whenever it does not run at a consistant rate.

GPS receivers are capable of providing an accurate time stamp as they are constantly receiving a time signal from each satellite that they can see. Most of them provide the current time in NMEA format over a serial connection, however, this time can be off by almost a second due to various factors, and is not reliable. To adjust for this, some GPS receivers have an output available on them that will proved a signal, once per second, which can be used as a time reference. This is known as the PPS signal (pulse per second), but it isn't available on most consumer grade receivers. The Garmin 18x LVC is one low cost receiver that does provide this signal, though. It comes as a bare receiver which you can connect to a 9 pin serial connection to your PC, or you can buy it from some places (such as the one linked) with a serial and USB connection on it, serial for data/PPS and USB for power.

Your average USB GPS unfortunately won't be able to provide the signal that we need.

Your easiest option if you simply want a fairly accurate system clock and don't have a PPS GPS receiver would be to install NTPD for Windows, and configure it to use the Australian NTP pool servers. This would be acheived by using the following ntp.conf file (in C:\Program Files\NTP\etc\ntp.conf):


server 0.au.pool.ntp.org
server 1.au.pool.ntp.org
server 2.au.pool.ntp.org
server 3.au.pool.ntp.org

driftfile "C:\Program Files\NTP\etc\ntp.drift"
However, your system clock could still potentially be off by a significant amount if it has not been running for several hours with a reliable network connection. The Meinberg NTP monitor allows you to see how much your "offset" (clock error) is in milliseconds from the servers, so that you can see if you have a good synchronisation.

I'd be happy to go over details if you want, via PM :)

Regards,
Eric

[citivolus]

I should probably mention that none of the above is necessary to simply observe this event. All of that is intended for super-accurate timing, but binoculars and a stopwatch in this case will get you 90% of the way there :)

[[1ponders]]

Cheers, thanks for that Eric. My connection is not stable enough for NTP I don't think. I can get more than a dozen dropouts a day on my satellite connection so I think if I want to get into this I'll need to look at the GPS option.

I don't think I'd be able to get the Garmin one in time for this event, but it is certainly an option I'll look into. I will be intouch. Thanks.

[[1ponders]]

Also I guess if my capture frame rate isn't too high and the event is short enough frame drops could be kept to a minimum.

[jjjnettie]

I've one you could borrow, but getting it to you in time, that's the problem.:shrug:

[[1ponders]]

Do you have the Garmin one? If you do then express post would get to me by mid week. I've got a GPS unit at work I could use (don't know if I can USB connect it though :confuse3: ) but I don't know if its one that is suitable and accurate enough. I wonder if one of the GPS units that plug into mounts would be suitable and if it could be used to plug into a laptop.

[jjjnettie]

Sorry to get your hopes up, it's not the right unit.

[[1ponders]]

Ah well, thanks for the offer.

[AstroJunk]

You guys have been busy!

I think that beeperSync to set the pc clock and Gstar3 to record will get a +/- 20ms accuracy, which is outstanding. I'll give instructions later of how to achieve this (and I need to do some calibration tests too).

This star is brighter than a Galilean satellite - so there will be no issues of capturing it live on a gstar/dmk/toucam/malincam/watec live even on a 80mm scope i would have thought.

More later - I have chores to do now :(

[[1ponders]]

Jonathan, I've downloaded beeperSync but I'm having trouble getting a Sync. Maybe you can tell me what I'm doing wrong.

1. set priority high
2. set connection broadband (I'm non satellite. I've tried the dial-up option as well)
3. selected ntp0.cs.mu.OZ.AU & ntp1.cs.muOZ.AU & tick.usno.navy.mil (which is what I normally sync my laptop clock to)
4. Click Get Tim Sync
5. Graph at the top (Syncronising and calibrating) goes and goes and goes (a few minutes)
6 Message "Syncronization was not successful. Please try again."

Just out of interest I tried to sync my laptop normally through tick.usno.navy.mil and had np.

[AstroJunk]

Interesting...

I have just tried with mine and no issues with getting the time - However, on my Win7 machine i had to run as administrator to actually set the time. I can't test on vista, but my xp machine was fine too.

Could it be to do with security?

[[1ponders]]

Not sure. I'm the only one that uses this machine so it starts up as administrator anyway. I wouldn't know where to start to look for security issues, however I did have firewall, antivirus, spyware and adware and all other security type prog turned off.

I'll give it another whirl.

[citivolus]

tick.usno.navy.mil, being located across the Pacific, will get you a lot of "jitter" or instability within your time source, due to differences in routing between subsequent network packets. The Australian servers mentioned are technically stratum 1 (or rather, top level, highest authority) and use a GPS reference clock, as is my server at home. I've spoken to the person who originally was responsible for setting up and maintaining those servers, as we know each other from a separate pursuit, and he has suggested that they may be of some questionable stability at this time, due to being hand rolled and using aging hardware. It was suggested that one not become too reliant on the existence of those UM servers due to a number of reasons, these included.

The CSIRO operates a number of time servers around the country, but access to them is by private individual agreement as they have been abused in the past. There are also many servers in the NTP "pool" which provide public access, but most of them are just referencing the UM and CSIRO server time anyway. I would also be willing to open my server up for queries from the astronomical community, once I relocate my GPS antenna.

In the short term, I would recommend using one of the recently updated AU servers from this list:

http://support.ntp.org/bin/view/Servers/StratumTwoTimeServers

Specifically, Brisbane area people would be well served by ntp.wfsltd.com.au and ntp.sjkwi.com.au

If you are on Internode, ntp.on.net is also available. It is generally sub-ms accuracy.

A number of the servers which I have tested against across Australia are of dubious time accuracy, being off by anywhere from 2 to 17 milliseconds. This includes many top level (Stratum 1) servers, which are supposed to be accurate to the microsecond level. We don't really have a good time infrastructure for public access, unfortunately.

Regards,
Eric

[AstroJunk]

A quick guide to FREE occultation timing!

Ok, the very best that one can hope for is a time of +/- 10 ms. That is simply a limitation of the cameras. We use a standard called PAL in Oz, and that runs at a frame rate of 25 fps and each frame can be further split into 2 fields and measured individually. This gives in effect 50 20ms exposures every second.

If you happen to have the occultation hardware such as KIWI-OSD, then the whole thing is made simpler by a GPS derived time which is overlaid on the video stream and can be captured by whatever device for later analysis.

If you don't have such a thing - fear not as a couple of freely available programs are available that will do the trick very well indeed.

The first is BeeperSync: http://hristopavlov.net/BeeperSync/ (http://hristopavlov.net/BeeperSync/) This program is designed to set a great device called a beeper box wich is used for occultation timing. Luckily for us, the way it does it is by first setting the PC clock to within a very high tolerance using internet time servers. Run it and press the Sync Time button. The software will tell you how accurate it judges to have made the sync. Repeat until within single figures!

The second program is Gstar3 (very recently upgraded): http://www.myastroshop.com.au/guides/gstar/ (http://www.myastroshop.com.au/guides/gstar/) Not content with just producing the most sensitive video camera, the guys have also produced a pretty good capture program too. This latest version has a check box to add UTC timestamp in the session settings. The time stamp is added to every frame and to millisecond precision. Nice. HOWEVER - be aware that GSTAR3 can't bust thought the old 2Gig file size limit yet. That equates to only about 2 mins of full speed video, so don't start running it too soon.

If you get lucky, Limovie will help you analyse your trophy: http://www005.upp.so-net.ne.jp/k_miyash/occ02/limovie_en.html (http://www005.upp.so-net.ne.jp/k_miyash/occ02/limovie_en.html)
but more of that later

There are some inbuilt latencies in the system which need to be subtracted from any measured time - the Gstar camera retards the signal by 20ms and the GSTAR3 uses the time of the end of the frame I think so you will need to subtract about 30 or 40 ms to get the best approximation of the actual event time, but overall a time accurate to +/- 20 ms is easily achievable with any PC with an internet connection. This is outstandingly good :)

[[1ponders]]

Any advice for us non Gstar users Jonathan? I'll probably use a DMK

[AstroJunk]

Oops, forgot to make it clear that the Gstar3 program should work with any camera, not just our beloved Gstars!

Hopefully that includes your DMK :)

[[1ponders]]

I'll give it a go Jonathan. Bit of training to do before the 10th then. ;)

[coldspace]

Way, way, way,way over my head now:eyepop: all this timming stuff. Its a computer science that I have trouble following.

I will just be happy if I get to see it happen on my CRT and capture it onto a video feed ;).


Matt.

[AstroJunk]

So will I Matt; so will I :thumbsup:

[jjjnettie]

It's a very intuitive program Paul, if I can use it anyone can.:D

[citivolus]

It isn't looking good for me tonight, due to random showers moving through my area and my equipment not being in an observatory. Hopefully this stuff clears out in time for me to set up, although this type of weather pattern seems to hang around for days sometimes.

[AstroJunk]

Yes, its looking a bit grim right now. My dry run (no pun intended!)yesterday was in under ideal conditions.

[[1ponders]]

Fingers crossed it stays fine. It clear here atm, seeing is pretty poor, but you get that at only 17 deg alt. Here's hoping for a moment of 10+ seeing at T-60 to T+60 :thumbsup

[AstroJunk]

Locked and loaded, live with the 20" and 3". Should be spectacular if it goes.

I can even see theta Ceti with the naked eye in the East which is good from my site.

[[1ponders]]

Chasin' clouds here now. 5 min and counting.

[citivolus]

Clouded out :(

Hope you all had better luck!

[[1ponders]]

Well here's hoping I picked up that ellusive couple of sec somewhere withing the 15 min of AVI on two laptops. 8" SCT with DMK21 and ED80 with the ol' faithful ToUcam 840. :thumbsup:

[astroron]

Best of luck Paul:) I didn't notice anything different:(

[coldspace]

No luck here either:(, thick clouds all over the East. Have lots of cloud breaks everwhere else but none on the east.
Bit disappointing as I was all set up with the IC capture ready and waiting.

Regards Matt.

[AstroJunk]

A clear miss from me. Well done for trying everyone, lets hope someone turns something up:thumbsup:

[[1ponders]]

I have quite a few thousand frames to work through. I was lucky enough to get about 2 min before through to 15 min after. The Sky6 gave the closest approach around 8:05 so I imaged the whole way through til about 8:08. 1575 frames for each 120 sec run.

Anyone like a avi to work through :P

[[1ponders]]

Does anyone have a better idea now of a time of closest approach? Or a link to a webpage with that info?

[AstroJunk]

19:57:01 +/- 10 sec for me. Yours won't be very far away from that, and will be earlier if anything but by no more that 20 seconds. It is always worth checking a minute or two around the prediction, but don't go too far.

http://www.asteroidoccultation.com/2009_10/1010_3995_18539_Map.gif

I wouldn't know how acurate Sky 6 is for predictions, but the data presented by OW has come from the uber-gurus.

[[1ponders]]

Thanks Jonathan

[jjjnettie]

I had a clear shot for the entire time. Though I didn't notice it visually via the gstar, I'm yet to go through the entire avi.

[AstroJunk]

It's always worth a second look even though to saw nothing. I once found a short event (of a different occultation) nearly a minute late that i hadn't noticed at the time!

You never can tell...

If anyone is up for more punishment, there is a nice event at 4am next monday morning ;) http://www.asteroidoccultation.com/2009_10/1018_1708_18827.htm

[jjjnettie]

I have a dimming of the star around 7.56.33.
It's probably just the seeing though.

[Outbackmanyep]

Hi Nettie!

If you look at your field, see if you have any other stars in the same frame as the target star, if your target star dims and you also notice your other stars dim then it's probably not a genuine occultation, ie it could be atmospheric turbulence or cloud........

Play it back and see how you go!

If not, try and get your avi to Jonathan who can run it through LiMovie.
:thumbsup: