Re: About APCC and ISS tracking and PC Time

Dale Ghent

Ugh. Windows' built-in time client has been a pain to deal with and performed sadly only until recently, and even still it requires some tweaks in order to keep host clock drift reasonably in check. One of the time server vendors I've used in the past has a decent series of KB articles regarding this:

As for using a GPS to sync the signal timecode to the host, I do this now using a $15 USB GPS dongle from Amazon and the NMEATime2 app from VisualGPS:

NMEATime2 does it right, including calibrating for the delay between the signal being emitted, received, and working its way through the OS to the app. This delay calibration is key for any app that's used to keep time with any signal source and why you can't just read the GPS sentences as they come off the serial port and write that time to the OS clock. It's pretty good for $20 and change, and a total solution for under $40 if you include the cost of any USB GPS dongle.


On Apr 7, 2021, at 21:08, W Hilmo <> wrote:

Your computer should be able to sync time with NIST, as long as you have an internet connection. APCC can then update the mount’s time with the computer’s time. This doesn’t require a new feature.

The new feature that I would like to see is for APCC to have an option to update the computer time from a GPS receiver. I do a fair amount of imaging from sites with no internet. Right now, I have a 3rd party piece of software that I use to sync the computer clock from the GPS, but it would be nice to have an option to do this right from APCC.

From: <> On Behalf Of drgert1 via
Sent: Wednesday, April 7, 2021 2:02 PM
Subject: [ap-gto] About APCC and ISS tracking and PC Time

Hello All,

There was a nice ISS pass yesterday. I tried to follow it with APCC horizon utility.
I see the PC time as the most tricky parameter. In my case the mount was trailing the ISS by a bit.
Obviously my PC time wasn't spot-on. Now for folks like me who are getting forgetful maybe it's an opportunity for Ray to put some automated NIST time sync into APCC just as a helpful measure. Maybe with a little popup 'OK' button.

The tracking feature is just great. I like the way it is organized sending the custom tracking speeds to the mount (which you can see in the driver UI)

My one improvement request would be to have the hand controller buttons 'N E S W' able to overlay the motion of the tracking. When I pushed the buttons during the ISS flyover the mount moved but 'something was fighting' the motion and pushed the ISS back to the edge of the field of view.

Maybe even have an option for a USB joystick to control the mount motion. (This would be even a cool thing outside off ISS tracking) :-)

Of course a great shout-out to Ray for the excellent work.


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