|
Hi, I would like to try occultation observing and provide data to upload. I would like to use a planetary camera that I have, ZWO ASI224MC,? but not sure how to get GPS time to it.
|
Hi Leonard,
This can be done. ? Please join the IOTAoccultations group.io
where there will be a lot of advice for you.
Wishing you good observing.
Tim
(UK)
On 22/11/2023 19:15, Leonard Ward
wrote:
toggle quoted message
Show quoted text
Hi, I would like to try occultation observing and provide data to
upload. I would like to use a planetary camera that I have, ZWO
ASI224MC,? but not sure how to get GPS time to it.
|
Leonard,
Ive not seen any other responses to your question (so far), so i will add some food for thought. The purpose of GPS is to control the computer clock. You could look at the TIMEBOX which is a GPS receiver that plugs into USB2 and controls the system clock (W10/11 preferred). Or you could build your own RasPi GPS to do the same. I know some folks have done this if you have these DIYskills.? The simplest option is to download Meinberg software to control the clock over the internet (NTP). This is prone to time errors, but with care it will work, but will always be second-best to GPS.
Ive not used a colour CMOS but it will be a magnitude less sensitive than mono.? ?It would be helpful to know where you are based, and what instrument you will use, so that you can reach out to a local group for more direct practical advice, and someone who has the software installed to give you the feedback.? ?And I refer to OW, Occult4, Tangra, and PyOte.
Looking at the future, there are some very nice gps-cameras now (mono) that have gps build in, so no timing problem. If you go down this route i would not consider the TIMEBOX of RasPi-gps.
All the best - Tim.
|
Good morning, there are reliable solutions with a GPS module, the <<NTP Time Server Monitor>> software and the file configuration <<ntp-4.2.8p15-v2 >> from Meinberg on a recent PC. Just copy these few lines into the NTP configuration file here:
# Add GPS clock server 127.127.20.3 minpoll 4 maxpoll 4 mode 16 prefer fudge 127.127.20.3 refid gGPS time2 0.1275 # Add PPS driver server 127.127.22.3 minpoll 4 maxpoll 4 fudge 127.127.22.3 time1 0.004 refid kPPS
Accuracy is +/- 1ms With this method your PC is on very precise time after 5 minutes, no need to wait like other software 30 minutes to 1 hour..
Your module generates a COM port number that must be entered in NTP(configuration) from the start of the configuration just below the country. Ex: 127.127.20.(com port number)
If you have any questions..
Karim Saci
trd google
http://www.astrosurf.com/topic/163700-ma-synchronisation-dun-pc-au-1pps-offline-pour-les-occultations/?tab=comments#comment-2338266
|
The short answer:? Use a GPS flasher.? NTP is not a good idea.
Although it is possible to accurately synchronize the PC clock with UTC, you cannot easily guarantee enough accuracy with the timestamps for the exposures.? The major challenge is measuring the delay between the start of exposure at the
camera and the time the capture software requests the system time (to generate the actual timestamp).? This delay varies based on several factors which are not in your control:? the camera firmware, the camera configuration, the camera device driver, all other
windows device drivers, and all windows subsystems.? The greatest risk is probably Windows.? Windows is constantly firing off various automated processes which may, or may not, impact the delay factor mentioned above.? In addition, the overall behavior and
timing profile of Windows can change with every Windows update.? Even if I took the time to measure this delay prior to every recording session, I would not trust the times due to the lack of control over other drivers and processes in Windows.? Window, Linux,
Mac are all about the same – none of these operating systems are true real time operating systems where the system can enforce timing requirements.
?
GPS Flasher:
If you are comfortable with small electronics projects, you could build a flasher based on one of Aart Olsen’s Arduino designs (posted to the files section of the main IOTA mailing list).? Otherwise …. a group of people is currently working
on a “productized” GPS flasher.
?
Steve
|
Hi Karim;
? I thank you for your help. Is this the way the lines should appear in the config file? I have not determined the com port yet.
# Add GPS clock? server 127.127.20.3 minpoll 4 maxpoll 4 mode 16 prefer? fudge 127.127.20.3 refid gGPS time2 0.1275? # Add PPS driver? server 127.127.22.3 minpoll 4 maxpoll 4? fudge 127.127.22.3 time1 0.004 refid kPPS
[Edited Message Follows]
Good morning, there are reliable solutions with a GPS module, the <<NTP Time Server Monitor>> software and the file configuration <<ntp-4.2.8p15-v2 >> from Meinberg on a recent PC. Just copy these few lines into the NTP configuration file here:
# Add GPS clock server 127.127.20.3 minpoll 4 maxpoll 4 mode 16 prefer fudge 127.127.20.3 refid gGPS time2 0.1275 # Add PPS driver server 127.127.22.3 minpoll 4 maxpoll 4 fudge 127.127.22.3 time1 0.004 refid kPPS
Accuracy is +/- 1ms With this method your PC is on very precise time after 5 minutes, no need to wait like other software 30 minutes to 1 hour..
Your module generates a COM port number that must be entered in NTP(configuration) from the start of the configuration just below the country. Ex: 127.127.20.(com port number)
If you have any questions..
Karim Saci
trd google
|
Le dimanche 26 nov. 2023 à 16?:19, Leonard Ward a écrit :
<<Est-ce ainsi que les lignes devraient appara?tre dans le fichier de configuration ?
Oui
|
To Steve, there is a delay between the GPS time and the recording of the video, this is easily adjusted with a PPS LED flash.
|
“To Steve, there is a delay between the GPS time and the recording of the video, this is easily adjusted with a PPS LED flash.
”
?
You can use the PPS signal of a GPS receiver to measure the difference (delay) between GPS time and the System timestamps.? But this GPS/SystemTime delay can vary significantly based on the factors I mentioned earlier (e.g. Windows process
starting/stopping, other device drivers, Windows updates, etc).? If you measure the GPS/SystemTime delay now, it may be different five minutes later and different again an hour later.? As a result, you cannot generate reliably accurate times by adjusting system
timestamps.? For reliable timestamps, you must reference the exposure times directly to the PPS signal via a methodology with known accuracy.
?
For example:
Various “flasher” devices (e.g. TimeBox, Aart’s flasher, etc) provide a direct reference to the PPS signal by marking (PPS LED flashes) exposures at the beginning and ending of an event recording session.
?
Steve
?
|
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. ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Steve Preston via groups.io
Sent: Monday, November 27, 2023 12:58 PM
To: [email protected]
Subject: Re: [OccultWatcher] How to use a planetary camera for occultations? “To Steve, there is a delay between the GPS time and the recording of the video, this is easily adjusted with a PPS LED flash. ” ? You can use the PPS signal of a GPS receiver to measure the difference (delay) between GPS time and the System timestamps.? But this GPS/SystemTime delay can vary significantly based on the factors I mentioned earlier (e.g. Windows process starting/stopping, other device drivers, Windows updates, etc).? If you measure the GPS/SystemTime delay now, it may be different five minutes later and different again an hour later.? As a result, you cannot generate reliably accurate times by adjusting system timestamps.? For reliable timestamps, you must reference the exposure times directly to the PPS signal via a methodology with known accuracy. ? For example: Various “flasher” devices (e.g. TimeBox, Aart’s flasher, etc) provide a direct reference to the PPS signal by marking (PPS LED flashes) exposures at the beginning and ending of an event recording session. ? Steve ?
|
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:
toggle quoted message
Show quoted text
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.
|
On Sun, Nov 26, 2023 at 04:13 PM, Steve Preston wrote:
The major challenge is measuring the delay between the start of exposure at the camera and the time the capture software requests the system time (to generate the actual timestamp).? This delay varies based on several factors which are not in your control:? the camera firmware, the camera configuration, the camera device driver, all other windows device drivers, and all windows subsystems.? The greatest risk is probably Windows.? Windows is constantly firing off various automated processes which may, or may not, impact the delay factor mentioned above.? In addition, the overall behavior and timing profile of Windows can change with every Windows update.?
Steve, there is no latency with this system, it's 100% digital and the offset is adjusted after recording, that's precisely the major challenge. On the graph that I posted you see the tracking over a whole day with one or two interruptions on my part from the GPS, we notice the precision of +/- 1ms. In addition, this graph was made under the clouds and indoors, which disadvantages the signal but is still precise.
trd google
|
On Mon, Nov 27, 2023 at 12:41 PM, smrussellau wrote:
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.
NMEATime2 does the same thing with the same precision as NTP Meinberg.
|
Saci,
?
You posted a chart from a program called “NTP Plotter”.? This looks like a measure of the offset between the system clock and a reference clock.? The chart doesn’t provide a lot of detail on the reference clock.? ?But let’s assume the reference
clock is a PPS signal from a GPS receiver and additional assume that there is no significant latency in measure the difference between the PPS signal and the system clock.? In this case, the chart demonstrates that the system clock with accurately synchronized
with UTC.? I have no trouble believing the system clock can be accuracy synchronized with UTC (as I think I said in an earlier post).? However, this is not good enough to generate reliably accurate timestamps for the incoming image data from a camera connected
to the system via USB. ?As I tried to describe earlier, the more significant latency issue is the timing of the data: the delay between the start of the exposure in the camera and the time the image data arrives in the code that requests the system time (for
the timestamp).? ?This “image communication delay” is highly variable and dependent on a variety of factors which are not in our control.
?
Steve
|
On Mon, Nov 27, 2023 at 10:31 PM, Steve Preston wrote:
You posted a chart from a program called “NTP Plotter”
It's just an app that reads Meinberg files in graphic form that's a little bigger than the original. Well apparently you haven't read the major challenge, I repeat the offset is adjusted once the recording is finished there is no more latency you can even have an advance on the timestamp. You must try this method, it is the most precise with a recent computer.
|
Test pps saturday suite graphique
advance 1ms
|
?
“repeat the offset is adjusted once the recording is finished”
What is the basis for making an adjustment after recording?? It would help if you can provide a more complete explanation of your methodology.
?
Thanks
Steve
|
In the configuration file there is the offset adjustment in "Timer2 0.00".. which must be set to zero then a SER must be carried out at 1000fps by reducing the format with SharpCap. You open your SER then you adjust the delay between the led/pps signal and your timestamp. see astrosurf link below.
http://www.astrosurf.com/topic/163700-ma-synchronisation-dun-pc-au-1pps-offline-pour-les-occultations/?tab=comments#comment-2338266
|
Sorry for the confusion.? 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?? The system timestamps will be offset from the actual camera Exposure start times by
a value of X seconds.? How do you determine the appropriate value of X?
?
Steve
?
|
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
toggle quoted message
Show quoted text
-------- Original message -------- From: jerryrst <jroyston@...> Date: 2023-11-27 9:23 a.m. (GMT-07:00) 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.
|
Tim Haymes
Saci
smrussellau
