Timing occultations

[Spica]

Planning to try timing occultations. Will begin with moon occulting stars for practice, and then hopefully - if opportunity is given - move on to asteroids occulting stars. Have downloaded Occult 4 which seems like really advanced software, as well as the IOTA manual for reference. I will observe visually.

So, which is the best way to get the correct and exact time?

What I have heard, GPS may not be correct at all times, and Fort Collins Colorado, US, time signal is not heard my way...regardless FQ. Just too far across the pond!

BBC have I guess "the pips" every hour. Maybe that's the best option. Do you all start the stopwatch on the full hour then, and just let the watch run to the occultation, regardles if its 1 min, 5 mins, 15 mins or 59 mins after the hour? I guess it can be done the other way too.... start at the occultation, and then just let it run to the full hour signal and read. Whichever you find best?

Any other hints?

Tnx

[LeoLion]

Hi , You could build a DCF receiver How to build a DCF77 receiver for PC . Conrad do them for under 10 squid & I believe Maplin do too. Have a look here too MSF Receiver modules | atomic-clock.galleon.eu.com . Have a look on here for WWV Simulators Simple Software . Take note these are exe files I have had no problems but be careful. This gives an audible WWV bleep simulation. A digital stopwatch will be great to use with the radio clock 'bleeps'. You will also need to sort out your 'personal equation' for the stopwatch timings. You appear to be looking at the right source material for the job!

I must not forget that we have our own precision VLF time source , MSF (It was Rugby but it is now broadcast from Anthorn in Cumbria .Have a look here Time from NPL - Wikipedia, the free encyclopedia . Do a search on here for occultations as the BAA UK Co-ordinator was registered on here , I think.

[Spica]

Thanks LeoLion. I like the simulator idea, although I am at a Mac right now and unable to check it. Will do that when I get home tomorrow.

The DCF & MSF are neat, I just don't know if it's reliable enough...? Been to a few stores retailing these, and all of the radiocontrolled clocks on the shelves show different sec's, even though the "online" symbol is lit! Don't know how to interpret that!

If they all have a signal I guess they'd be showing the correct time!?

I prefer the timesignal over shortwave radio I think, for the sake of reliability, but both Fort Collins and Moscow are ruled out. Doesn't BBC have a signal every hour, still? Read Finish YLE has something too, but not sure how often.

[TimH]

Hi Spica,

For lunar occultaions I use a digital stopwatch bought from MAPLIN and the BT time service (123 speaking clock). The alternative is an MSF or DCF receiver giving a clear audible second/minute output. (see Leolion). But I have moved on from visual work and use video (WAT 120N) with a GPS time overlay. Accuracy is +/- 0.02 s for Lunar Occs and 0.1 to 0.3 for asteroid occs (good enough) as the objects are fainter.

[LeoLion]

The DCF and MSF signals are very precise but the digital/watch/clock may only synchronise (say) once per day and ( as you say that is the weak link causing variations ) . Using the VLF radio receiver circuit and using it to bleep a piezo bleeper gives you a precise time changeover at the end of the missing 59 th second bleep ( See the DCF Wiki DCF77 - Wikipedia, the free encyclopedia).

[Spica]

Aha, never got that you also may LISTEN to the signal driving the DCF & MSF accurately! That puts it in a different perspective. Neat! That's what I need, I'm certain. Would you say it's recommended to start with the moon occulting stars, and then move on to grazing & then asteroidal - or is it not much of importance where to start...? I guess perhaps one should go for what's being served on the sky and not put up a particular order of things?

[Spica]

Does anyone know if these come already assembled with piezo beeper and all? If so, who has them?

[TimH]

Spica: When I do a graze, I use an old digital DV camcorder as a tape recorder. There is an internal clock that can be set manually to UT. The time of events can deduced to 0.5s which is Fine for grazes.

If there are lunar occs, do time them. I send my observatons to the BAA coordinator in the Lunar Section. Grazes - The next one for me 2B Cnc on March 4th near Aylesbury (about 1hr drive).

For asteroid occultations you need predictions for your area and select the ones within visual range. There may be some here: Asteroid occultation tracks UK 2011 The list is for the whole UK. For visual detection the magnitude drop at occultation should be 1 magnitude or more. Only a few events result in a total dissapearance of the star (unlike a lunar Occ).

[Spica]

Thanks Tim, that's another great way it seems. All of a sudden there are lots of options!

I have mailed IOTA/ES abt a week ago as I would like to join in, but they don't reply on mails. Perhaps my e-mail is blocked in a spam filter somewhere... Anyways, my question to them was if I can use my credit card for membership fee, as this Euro-check system seem like a lot of hassles. The US-branch has no issues with cred.cards and/or Paypal.

[TimH]

IOTA-ES can be joined with Paypal now. Maybe we can continue off-line? I can be contact at occultation@baalunarsection.org.uk

The main tool for asteroid occ observers is the PC program OccultWatcher : Occult Watcher

You may know about it. Cant recommend it strongly enough to an asteroid occultation observer. With this you wont miss out on any good events.

[Spica]

Thanks Tim. Just mailed you!