SharpCap Timestamp accuracy

Anything that doesn't fit into any of the other forums
Posts: 5
Joined: Sat Jul 21, 2018 12:21 pm

Re: SharpCap Timestamp accuracy

Post by Astrojunk » Mon Jun 03, 2019 11:54 am

Hi all, another Occultation timer here - I never knew there were so many of us :)

I've been dual recording events from my observatory using a video setup timestamped with IOTA-VTI and with an ASI174MM using NTP timing and can say that I can't find a significant delay using (the magnificent) SharpCap.

I'm currently doing a lot of lunar occultations using very high frame rates with very small regions of interest to generate stunning diffraction curves at 1000fps which are identifying many companions hiding in their midst.
Fresnel eg.jpg
Fresnel eg.jpg (21.78 KiB) Viewed 431 times
There's a slo-mo here ... 320681123/ on my FB page of water drop experiment - we are so lucky to have this tech at our disposal. I hope to be doing some further timing experiments in the not too distant future with a more advanced rig than just pointing at my IOTA-VTI, but here are the results from that:
NTP Test.png
NTP Test.png (121.01 KiB) Viewed 431 times
It's interesting that no one can quite explain how well it works...

Posts: 20
Joined: Fri Mar 16, 2018 9:27 am

Re: SharpCap Timestamp accuracy

Post by Furgus » Thu Nov 21, 2019 11:52 am

Hi All,

I have noticed a significant change!

Can I summarise what the timing situation used to be, this copied from my previous post:

"Firstly, when testing my usual laptop with my GPS server, I found that with an exposure time of 400ms or shorter, Sharpcap was stamping at the start of a frame, while an exposure setting of 450ms or above was stamped at the end of the frame."

I now notice that since Windows 10 update 1903 (in fact thats a new version of W10) ......that ALL time stamps are applied at the END of the exposure for each frame. Suddenly its working as Robin says it should (why previously it was applying a stamp at the beginning of the frames seemed to be a mystery).

Everything still seems nicely stable......can anyone suggest why this might have happened?!!
The change can easily be accounted for in my observations, in a way I'm glad its working as it should.
Every observation would include a check w.r.t. the 1PPS light flash, so not a problem.

All the best


User avatar
Site Admin
Posts: 4322
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK

Re: SharpCap Timestamp accuracy

Post by admin » Thu Nov 21, 2019 6:35 pm


I have to say that that sounds like a weird change to happen with Windows update. I will just note that with the latest SharpCap 3.2 update I changed the DATE-OBS fits header so that it will try to be as close as possible to the start of the frames capture rather than the end. I don't think this will affect you though.

Cheers, Robin

Post Reply