USB 3.0 Extension Cable with ZWO ASI294MC Pro

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poolemarkw
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USB 3.0 Extension Cable with ZWO ASI294MC Pro

Post by poolemarkw » Fri Feb 01, 2019 2:25 am

Hi Everyone,

I'd like to use a long USB 3.0 extension cable with SharpCap and my ZWO ASI294MC Pro camera so I can use SharpCap inside my house when it's cold outside. I bought and tried a 32' active USB 3.0 extension cable both with and without the included 5V power supply and in both cases SharpCap can't find the camera. Anyone successfully doing this? If so, please explain what cable/settings worked for you.

Thanks,

Mark

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turfpit
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Re: USB 3.0 Extension Cable with ZWO ASI294MC Pro

Post by turfpit » Fri Feb 01, 2019 12:26 pm

Mark

You don't mention:
  • The make/cost of cable you are trying to use.
  • The make/model of PC/laptop.
  • If a USB hub is involved.
All the above can potentially affect a successful outcome.

If I was trying to run a USB3 camera over a 10m cable (and I would be doing my utmost to avoid doing it in the first place) I would:
  • Go direct from camera > extender > capture PC's USB port.
  • Not go through a hub.
  • Ensure guide camera cabling was completely separate from the imaging camera.
  • Disable USB Selective Suspend on the capture machine.
I would try to make that distance with USB2 instead, as it is more stable, more forgiving of both cable length, doesn't require additional power and is more forgiving of the power output of the PC USB port.

I once did some systematic testing on USB2 v USB3 to assess the impact. Using an Altair 183C at full frame of 5000 x 3000 I captured 100x15s RAW12 images. These were 38Mb files. I calculated the time taken as the difference between the time stamp on the disk of the last and first image. The USB3 test took just over 30 minutes to complete, the USB2 took 35 minutes. Not much of an overhead in 100 frames. The USB2 test also completed in the same time using a 15m active extender cable (which did not require additional power).

For me, doing deep sky with exposures of 60s or longer, the time overhead is not an issue. If I was carrying out high speed planetary imaging then a rethink might be in order. I would always prize reliability over speed (having worked in the computer industry supporting operating systems for over 30 years).

As always with this type of thing, YMMV.

Dave

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Re: USB 3.0 Extension Cable with ZWO ASI294MC Pro

Post by BlackWikkett » Fri Feb 01, 2019 2:31 pm

All of Dave's Suggestion are very valid. I have read in the past it's a bad idea to run USB 3 camera's on USB 2. Not that they're not compatible but the USB 2 adds noise to images. This has something to do with the USB circuitry. I've searched for links about this but of course I can't find them.

If you want to image from the comfort of your cozy home I'd suggest setting up a dedicated laptop or imaging PC at the scope. Remote to this host computer and all the USB and other connectivity issues will go away. I'm relatively new to the astronomy hobby but it didn't take long for me to move inside with the host PC outside doing all the heavy lifting.

-Wikkett

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Re: USB 3.0 Extension Cable with ZWO ASI294MC Pro

Post by turfpit » Fri Feb 01, 2019 3:32 pm

setting up a dedicated laptop or imaging PC at the scope. Remote to this host computer and all the USB and other connectivity issues will go away
I agree with that. However, it does add, what might be for some, the complexity of network connectivity.
I have read in the past it's a bad idea to run USB 3 camera's on USB 2. Not that they're not compatible but the USB 2 adds noise to images.
Invariably this type of issue will be down to poor USB3 chipset implementation, poor cables/hubs or optimistic user hardware configuration (seen plenty of those). I have £1500 when new laptop from a reputable manufacturer which has a Renesas v0.9 USB3 chipset. The 183C camera would not run on the USB3 ports. There was no firmware upgrade for that hardware. That is why I did the USB3 v USB2 tests - find out for myself rather than rely on 'forum group think'.
I've searched for links about this but of course I can't find them.
Annoying isn't it, happens to me all the time. All I can offer is the standards definitions at https://www.usb.org/.

There was an article on CMOS imaging in the January issue of Sky at Night. It was written by world class imager Gary Palmer - who makes his living testing kit for manufacturers. He mentions to get from scope to his warm room, a distance of 7m, he uses USB2 because of stability. The camera he was using was a ZWO ASI 094MC Pro. This has an inbuilt dual USB2/3 hub which allows direct USB2 connect from camera. I wonder why ZWO implemented that?

At the end of the day, with USB3, the length is the killer. It can be overcome but needs correctly implemented hardware (read expensive) to be purchased.

Dave

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Re: USB 3.0 Extension Cable with ZWO ASI294MC Pro

Post by BlackWikkett » Fri Feb 01, 2019 6:24 pm

My understanding for ZWO USB 2 hub on their USB 3 cameras was to allow connection of guide camera / filter wheel. The additional potential USB 2 noise is more or less irrelevant. I've used the feature for guide camera before I upgraded my mount that has a built in USB 2 hub in the saddle. At the end of the day I'm sure USB 3 device on a USB 2 port is fine and the noise is more or less not an issue. If you're not doing any high FPS planetary imaging you're not loosing anything.

-Wikkett

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Re: USB 3.0 Extension Cable with ZWO ASI294MC Pro

Post by admin » Fri Feb 01, 2019 7:52 pm

Hi there,

Long USB cables are invariably a problem – the limit for a single run without a hub is less than 5 m for USB 2 and realistically less than 3.5 m for USB 3. That means that very long run needs multiple hubs (or the equivalent of a hub built into the cable) and these all add to the possibilities of something not quite working right. The length limits of USB cables are based on timing issues of how fast the signal propagates down the cable, rather than attenuation, so supposedly a higher quality cables will not really give you any advantage over the lengths laid out above.

Since USB is a digital system, it's very unlikely that you will get additional noise in an image due to using a USB 3 camera on a USB 2 cable – there is error correcting or at least checking built into the transfer so that if there is data corruption along the cable you will lose frames rather than getting a corrupted image. There is a possibility that if you're USB 3 camera does not get enough power that may affect image quality.

By far the best approach to imaging and to distance is to run a computer near to the camera and then remotely access that computer over Wi-Fi or a network cable.

Cheers, Robin

poolemarkw
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Re: USB 3.0 Extension Cable with ZWO ASI294MC Pro

Post by poolemarkw » Sat Feb 02, 2019 6:21 pm

Excellent responses everyone! I've ordered a couple of powered USB 3.0 hubs that I'll try next, and if not successful, will then try the remote PC solution.

Thanks for your help!

Mark

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