(ASI120mm) SharpCap ignoring exposure time, not updating image or polar alignment info

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Marlin
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(ASI120mm) SharpCap ignoring exposure time, not updating image or polar alignment info

Post by Marlin » Mon Nov 13, 2017 3:55 am

Specs: ZWO ASI120mm, Sharpcap 2.9 (included software), Windows 10 on Lenovo Thinkpad

Hello-
I'm not sure if this is the right spot to ask about this, so please point me in the right direction if it's not.
I'm using a ZWO ASI120mm camera, which came with SharpCap 2.9. When I went to use it last night, I came across an issue where the software was ignoring my exposure time setting and going for however long it felt like. Please see this image: https://imgur.com/a/YYE4g

On the bottom right, the exposure frames turned to x/-y, going for around 8 seconds at a time, regardless of what I set the exposure time to. I tried playing around with the different camera settings to see what might be causing it, but I couldn't seem to figure it out. This happened both in and out of the polar alignment process.

On top of this, sometimes the preview image wouldn't update, which proved to be a hassle when I was trying to use the polar alignment tool. I often ran into a case where I would be moving the mount but not see any kind of movement on the screen, only to have the image update and show me that I was now off in the other direction. The feedback was not consistent at all, sometimes not updating for 20 seconds at a time.

I'm new to astro-imaging software and CCD's, so I'm not quite sure what the cause might be. It was around 35-40 degrees last night - could the cold have something to do with it? I also had used a USB extension cable on a 2.0 port - could that have caused some kind of lag? Is there a setting I was overlooking?

Any advice would be helpful. Thank you.

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admin
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Re: (ASI120mm) SharpCap ignoring exposure time, not updating image or polar alignment info

Post by admin » Mon Nov 13, 2017 7:04 am

Hi,

the negative numbers in the time remaining indicate that the frame from the camera is overdue and that SharpCap is still waiting for it. A small amount of this is expected as it just represents the time needed to download the frame from the camera (especially for larger cameras). What you are seeing indicates a problem however.

It sounds like a USB related issue - try working through the steps in this post on troubleshooting USB problems - viewtopic.php?f=18&t=349

Another thing of course is to try SharpCap 3.0 which has a newer version of the ZWO SDK (maybe they have been fixing bugs that will help you). Do be aware though that Polar Alignment is a SharpCap Pro feature in SC3.0 (license required).

When you have issues like this it's always a good idea to test as much as possible in daylight - after all you don't really care what image appears on your 2s exposures, just that you can get them to come through regularly.

cheers,

Robin

Marlin
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Re: (ASI120mm) SharpCap ignoring exposure time, not updating image or polar alignment info

Post by Marlin » Mon Nov 13, 2017 1:52 pm

Okay - I will try eliminating the extension cord and connecting to the 3.0 port next time, and if that doesn't work then I will try upgrading to the Pro version. Thanks for the advice.

Edit: Just looked it up and apparently the camera I have is only USB2.0, so that's a bit of a drag. Still will connect it to 3.0 port just to be sure.

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Re: (ASI120mm) SharpCap ignoring exposure time, not updating image or polar alignment info

Post by admin » Mon Nov 13, 2017 7:05 pm

Sounds good - also remember to check the Turbo USB control - having that set too high can lead to the symptoms you describe.

cheers,

Robin

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turfpit
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Re: (ASI120mm) SharpCap ignoring exposure time, not updating image or polar alignment info

Post by turfpit » Mon Nov 13, 2017 9:42 pm

Marlin

This may *not* apply to you but just be aware of this. If it happens to you, the info might save you some time.

I have a ASI120MC, USB2 camera (no autoguider port). When plugged into a USB3 port on my Lenovo W510 laptop the camera is not recognised (detected) but does work when plugged into a USB2 port. This always puzzled me. However I stumbled upon the reason in the ZWO User Group Linux section - it appears the ASI120 USB2 version was implemented with a non standard USB packet size and to get the camera to work under Linux, people who were writing their own capture programs had to hack the kernel to get the camera to work. It appears the USB3 variants are implemented to USB 'standards'. This would explain why a USB3 port will not recognise the USB2 device (first time I have ever seen this).

Dave

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Re: (ASI120mm) SharpCap ignoring exposure time, not updating image or polar alignment info

Post by Marlin » Mon Nov 13, 2017 9:56 pm

admin wrote:
Mon Nov 13, 2017 7:05 pm
Sounds good - also remember to check the Turbo USB control - having that set too high can lead to the symptoms you describe.
I'll keep that in mind. I'll try auto first and see what it does. Should I leave it on high speed mode as well?
turfpit wrote:
Mon Nov 13, 2017 9:42 pm
When plugged into a USB3 port on my Lenovo W510 laptop the camera is not recognised (detected) but does work when plugged into a USB2 port.
I seem to recall when I tested it back inside that it did recognize it when plugged into 3.0.

I will have to pay close attention next time to see if something in particular causes it. Would the processing of the polar alignment cause any kind of input lag like I'm experiencing? It seemed to happen regardless, but even so.

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Re: (ASI120mm) SharpCap ignoring exposure time, not updating image or polar alignment info

Post by admin » Mon Nov 13, 2017 10:04 pm

Hi,

the polar alignment should not cause this sort of lag - it may take a second or two to build the plate solving index when you first activate polar alignment, but after that each frame is processed quite quickly (typically less than 0.25s).

cheers,

Robin

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