Flicking/jerky movement of image in Sharpcap

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js10
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Joined: Sat Nov 21, 2020 4:20 am

Flicking/jerky movement of image in Sharpcap

Post by js10 »

Hi. First post on this forum and still fairly new to amateur astronomy and astrophotography in general. As such, I'm still going through the learning curve when it comes to how to use the various products and programs required, and have hit a bit of a bump when it comes to Sharpcap. The last time it occurred, I actually took a video of it and was all set to attach it to this post, but apparently this forum doesn't allow video attachments (please let me know if there is some kind of workaround for this)! Explaining it visually would be MUCH easier, but as that doesn't seem possible, what I'll just say is that as the subject line suggests, what's happening is that I'll get a particular object (only planets so far for me) in my eyepiece, which will look fine, remove the eyepiece and attach my camera (the ZWO ASI 385) so that the planet appears on my laptop screen, and then once I start the capture, the planet will kind of jerk up and down on my screen. No, not the smooth drifting movement that I guess is to be expected, but it's like it disappears, appears again a few inches lower on the screen, and then bounces right back to its original position. Again, a bit hard to describe in words! Even so, does anyone have any thoughts on what could be happening here? Thank you.

PS. Oh, it's v.3.2.6383. Windows 7 on an Acer laptop. As stated above, camera is the ZWO ASI385.
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Re: Flicking/jerky movement of image in Sharpcap

Post by admin »

Hi,

firstly, if you want to share a video then the best thing to do is to upload it to somewhere like dropbox or one drive and then put the sharing link into a post here. The forums have limits on attachment types and sizes mainly to keep the size of data that needs to be backed up under control. As you say, sharing a video may be the easiest way to get a good understanding of what's going on here.

If you are only seeing problems once the start capture button has been pressed then it's possible that your PC could be struggling to keep up with the dataflow once it has the additional task of saving the data to disk as well as just displaying it on screen. If that's the case then it may be worth trying to use a subarea of the camera sensor to reduce the load.

Cheers, Robin
js10
Posts: 21
Joined: Sat Nov 21, 2020 4:20 am

Re: Flicking/jerky movement of image in Sharpcap

Post by js10 »

Thanks Robin! Good idea about the Dropbox. I'll get that together soon and post it -- this is kind of a busy and stressful week (I see you're in the UK, but as you probably know, it's Thanksgiving week here, and a strange one at that). But in the meantime, I have to ask. What do you mean by a subarea of the camera sensor? Is that something that can be (or has to be) set in SharpCap itself? Also, any idea why that would be the case? I mean, it's clearly not true of all users, right? So why would my PC, in particular, struggle to keep up? Low memory or something along those lines? I could use the subarea as you suggested, but I figure it would be even better to get to the root of the problem and try to fix it. Thanks again.
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Re: Flicking/jerky movement of image in Sharpcap

Post by admin »

Hi,

have a look at the documentation on setting the capture area to put your camera into a mode where we are only collecting the data from some of the sensor area - https://docs.sharpcap.co.uk/3.2/#!2!Cap ... and%20Area - basically just select a capture area that is about half the full size of the sensor in each direction.

At this stage I'm just hoping we can do some experiments to work out why the problem is happening – if it goes away by selecting a smaller capture area then it's quite possible that something (CPU? Disk speed?) Is being overloaded when the camera is running at full resolution. If reducing the resolution doesn't help then that's less likely.

Alongside any captured video showing the problem, it would be good to have the log from SharpCap (grab the contents of it after the capture has been attempted) - there may be useful information in the log. A full list of the camera settings and details of the camera model and PC hardware might be helpful too. You will get the camera settings in the .CameraSettings.txt file that is saved alongside the output video.

Cheers, Robin
js10
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Joined: Sat Nov 21, 2020 4:20 am

Re: Flicking/jerky movement of image in Sharpcap

Post by js10 »

Okay, as promised, following is a Dropbox link to a video clearly demonstrating the issue: https://www.dropbox.com/home/Miscellane ... 136119.mp4 . Hope this helps clarify! Thanks.

PS. By the way, you may have noticed that I just created another thread about a different issue involving file size. No, I do NOT think that the two issues are related, as this flickering effect has been happening well before lack of space became an issue.
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Re: Flicking/jerky movement of image in Sharpcap

Post by admin »

Hi,

I'm afraid that when I click on the link, dropbox gives me a message about the folder '/miscellaneous' not existing, and I don't see the file :(

Cheers, Robin
js10
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Joined: Sat Nov 21, 2020 4:20 am

Re: Flicking/jerky movement of image in Sharpcap

Post by js10 »

Ugh, okay. Thanks for letting me know. I'll deal with it and post again when I do.
js10
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Re: Flicking/jerky movement of image in Sharpcap

Post by js10 »

Hi. Could you please try it one more time? I absolutley did click "Share" and it gave me this link, so it seems like it should work. No?

https://www.dropbox.com/s/4b6j2d3aez47d ... 9.mp4?dl=0
celkins
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Re: Flicking/jerky movement of image in Sharpcap

Post by celkins »

Hi, just viewed your mp4, and I’d say you have USB transfer issues - if you look carefully, there are several tearing artefacts on the frames where the image jumps...
There is a very good section in the manual on debugging USB issues.
Regards,
Carl
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Re: Flicking/jerky movement of image in Sharpcap

Post by admin »

Hi,

I think Carl's diagnosis is right (and I can see the video this time – thanks for sorting that). The fact that the planet is jumping about is definitely a bad sign and frequently goes along with USB transfer problems. You can also see that during the short time that you have captured on video the number of dropped frames goes up by nearly 200 – it looks like about two frames are being dropped for everyone that is getting through.

Do have a look at the USB troubleshooting hints – the link is in the orange box at the top of this page. In particular try to keep to short USB cables with no hubs or extensions and try adjusting the Turbo USB and 'High Speed Mode' controls for your camera – turning down the Turbo USB may reduce the frame rate but could well make things run in a more stable fashion.

Cheers, Robin
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