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Synchronising UTC across my system.


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#21 Jay

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Posted 26 August 2016 - 01:51 PM

You can only adjust the time between exposures, otherwise you create a step in the tracking that breaks the image. But Autoslew does not know when you start/end your exposures...

 

In fact, the little drift of the PC clock has a good side effect: it creates an automatic dithering every 100 minutes!!!

 

Best regards.

 

Bernard

 

I usually take 20 min exposures, so a little drift every 100 minutes would mean that I have every 5th image with double dithering :)

 

Best regards,

Jay 


Edited by Jay, 26 August 2016 - 01:52 PM.


#22 maxmirot

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Posted 14 September 2016 - 05:38 PM

This is incorrect.

 

Review Autoslew time settings. The GPS updates the clock as frequently as you wish not just slews, start and stops. I have Autoslew using the GPS to update every 3 minutes. This should be fine for most any exposure.

 

 

Max



#23 MikePaling

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Posted 14 September 2016 - 07:32 PM

Hi ...

 

How to do set a GPS to make automatic updates during a session? I can't find this anywhere :-(((

 

Regards Mike



#24 RamaSpaceShip

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Posted 14 September 2016 - 08:48 PM

This is incorrect.

 

Review Autoslew time settings. The GPS updates the clock as frequently as you wish not just slews, start and stops. I have Autoslew using the GPS to update every 3 minutes. This should be fine for most any exposure.

 

 

Max

Hi Max,

 

The fact that the PC clock is updated does not mean that Autoslew takes it into account between slews.

 

Anyway, a GPS update every 3 minutes is useless and may have more bad effects that good ones as most applications are not prepared for such clock changes and may react in a weird manner. Such clock updates are highly discouraged (when not completely forbidden) in real time systems, and a PC running Autoslew is one of them.

 

I don't know which benefits you expect from such a high frequency, and I am curious to see figures that show that this is helpful.

 

 

How to do set a GPS to make automatic updates during a session? I can't find this anywhere :-(((

Mike, I don't know as I don't use a GPS, I use NTP instead, and it is configured to update the clock once per day. But if you update your clock with the GPS at the beginning of your session, it is highly sufficient, as no updates during the session are necessary.

 

Best regards.

 

Bernard



#25 maxmirot

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Posted 15 September 2016 - 10:39 PM

I hope that Autoslew would not allow  time to shift rapidly during tracking. 

 

How time  updates from GPS or NTP are handled are unknown

No way to tell without asking Dr. Keller. 

 

I am sure it would be helpful have subsecond time accuracy during an exposure for tracking.

 

Syncing at the start on an exposure or session updates the time offset. After that you are relying on the system or other clock source.

Time drift is not desirable during an exposure.

 

 

Max



#26 maxmirot

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Posted 16 September 2016 - 05:07 AM

I take it back.

Bring up the time settings menu for Autoslew with GPS it specifically says " Sync Query during tracking for GPS.

You can input the time interval. default is three minutes.

This strongly suggests  the time reference  is update by Autoslew from the GPS during an exposure.

 

Max



#27 RamaSpaceShip

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Posted 16 September 2016 - 11:37 AM

Yes, the PC clock is updated. But is it used by Autoslew during tracking? Not sure, but I would not take such a risk, as it can cause steps of several pixels that can kill your image.

 

But mainly, I do not see any benefit of such frequent updates, as the PC clock is precise enough. And if your PC clock is broken, I would suggest to quickly fix it, as using frequent GPS updates may not even be an effective workaround.

 

Bernard






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