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How to use a planetary camera for occultations

smrussellau All Messages By This Member #403 开云体育 Hi Graem ? The LED is flashed into the optical path at the beginning and end of the observation. ? You can use the flashes to work out the capture delay of your camera system and the offset of your PC clock. However, you will need to have the PC clock as close the accurate as possible, using either NTP or GPS to sync the PC clock to better than one second. ? The flashes can also help you work out if there is any jitter in the time interval between captures. ? BTW, you will find USB GPS dongles on eBay with a 1PPS flash if you don’t want to go DIY. Just use a USB extension lead to connect the dongle to your PC, and make up a clip to attach it to the front of your telescope. You could then use the GPS dongle to correct your PC clock. ? Cheers, Steve. ? ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Graem Schmidt Sent: Tuesday, November 28, 2023 5:47 AM To: [email protected] Subject: Re: [OccultWatcher] How to use a planetary camera for occultations ? Hello: I am not clear on one point - are you planning to shine the LED from the GPS module into the telescope with no gating (I.e. it could flash while the occultation is in progress?)? ? Graem ? ? ? ? ? -------- Original message -------- From: jerryrst <jroyston@...> Date: 2023-11-27 9:23 a.m. (GMT-07:00) To: [email protected] Subject: Re: [OccultWatcher] How to use a planetary camera for occultations ? Hello all, ??? I used a module with antenna. One can also attach an aerial. It has an LED wish flashes with the PPS, albeit not very bright. It has a PPS output on one of the pins, you could add an FET, resistor and LED to produce a brighter flash If the signal is weak you can attach an external GPS aerial, I have one on a 5m cable See for a suitable module Best wishes, Jerry Am 27.11.2023 um 12:40 schrieb smrussellau via groups.io: Hi all ? Thanks for the interesting discussion. ? Another source of 1PPS flashes are GPS dongles such as the Ublox7 et al. Cheap off the self solutions. ? These should work with software such as NMEATime2 to bring the PC clock well within the <1sec accuracy required to know which seconds the flashes correspond to while using capture software that uses the PC clock for timestamps. All you need is a USB extension lead to use the dongle as both a flasher and a ?time source. No need for Internet for NTP. ? Steve P, I hope to find the time to test this out prior to the next TTSO. ? Cheers, Steve R. ?
Saci Member Profile All Messages By This Member #404 Edited <<I’m not asking how you apply the adjustment to the times in the file.? I’m asking how you determine the amount of adjustment?>> How do I determine the value or rather the start of the second? that's it ? The amount of the adjustment is in milliseconds anyway recent PCs do not have precision greater than ms. Le GPS and the serial cable https://www.amazon.fr/dp/B0758B6MK6?psc=1&ref=ppx_yo2ov_dt_b_product_details
Graem Schmidt All Messages By This Member #405 Hi Steve Russell - I have been recording occultations for about a year now and I am currently using a LED flashed into the optical path as you mention.??? I have a GPS module that generates a PPS signal, but I feed that through an Arduino that is programmed to make sure flashes do not occur during the occultation as it would mess up the timing algorithms.? There are only a couple flashes produced by the Arduino and I know exactly what time they occurred.? Thus I do not need to use the PC clock at all. If I understand correctly, you are using a GPS dongle only, and thus flashes are always occurring at 1 PPS.? How do you prevent the flashes from happening during an occultation?? Are you manually just holding the GPS dongle in front of the telescope before the start of the occultation?? If this is the case, I would be worried about not holding it steady enough for the timing algorithm to correctly interpolate the exact time of the pulse.? And if I understand correctly, you are only training the PC clock so you know which LED flash captured in a recording corresponds to a particular second (by looking at time stamps)??? If you can detail your process, that would be great. Hi Steve Preston - Sorry that my message popped up in the middle of your questions.? I had posted about a day earlier but it was delayed probably because this was my first post on this forum. Cheers Graem
Saci Member Profile All Messages By This Member #407 Good morning,? I continue to monitor NTP Meinberg and I find that the more I use it, the more precise it is. I don't have to wait 1 hour for stability unlike NMEATime2. NTP Meinberg is operational after 5 minutes, on the go that's reassuring.? ADOPT for me.? Happy weekend everyone test début NTP Meinberg pps.gif test début NTP Meinberg pps 2.gif
Saci Member Profile All Messages By This Member #408 With Tangra file: test tangra samedi 2 dec.jpg fichier lc tangra.lc fichier lc tangra.lc
Saci Member Profile All Messages By This Member #409 Edited RE, One last important thing for my GPS to work well, you must only keep the GPS satellites (American) you must deactivate all the others in Ucenter (Ublox) otherwise it does not work. https://www.u-blox.com/en/product/u-center connecting the GPS: ? ? ? ? Ucenter VS.jpg branchement usb gps.jpg
TriAstro #410 开云体育 I have seen discussions of this NTP PC timing issue posted offline.? The issue is not that the observer can get good accurate timing at the PC, the problem is the timing at the PC is not the timing at the start of frame of the camera, and there is no way to precisely calibrate the time lag between the start of frame and the PC time.? The lag is not constant, hence there will always be error in the PC logged time stamps.? Unless I have misread the offline postings.? So getting an ultraprecise PC clock time is not going to necessarily get you an ultraprecise start of frame time on the video sequence. ? Tony George Scottsdale, AZ ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Saci Sent: Saturday, December 2, 2023 2:14 AM To: [email protected] Subject: Re: [OccultWatcher] How to use a planetary camera for occultations ? Good morning,? I continue to monitor NTP Meinberg and I find that the more I use it, the more precise it is. I don't have to wait 1 hour for stability unlike NMEATime2. NTP Meinberg is operational after 5 minutes, on the go that's reassuring.? ADOPT for me.? Happy weekend everyone
Saci Member Profile All Messages By This Member #411 A PC with good live timing cannot record a video with good recording timing I agree because of the latency it creates, there it is not the same thing there is no random timestamp it's all digital PCs since w8 are more efficient in managing the time and here with this system it's you who chooses the start of the second you have to try it.. it costs a GPS module and a good PC.. Karim
Saci Member Profile All Messages By This Member #412 Here with two GPS: the DCDTRAKER software from (tools)GENIKA which recovers the pps and NTP Meinberg signal. Nothing more to say about precision. You need the right serial cables to use it correctly (dcdtraker) ? ? ? ? fichier dcdtrack ntp meinberg.jpg

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