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I’m considering buying a ZWO ASI462MC camera for lunar and planetary imaging, I have a USB 3 socket on my PC but it is 5m away from the telescope plus a USB 2 hub to my devices I.e another 2-3m which works fine with USB 2. Just wondering what the impact on frame rate would be running the camera on the USB 2 connection? Thanks, Rob |
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| I expect a considerable reduction in frame rate over USB2. Do not use a hub. That can make things considerably worse. |
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| Thank you Andrea, I think I’ll have to buy something along the lines of the ASIair wireless hub to make the most of the frame rate. |
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| Or a Pegasus power box. Just another option that would allow you to use your PC still, while options to power other things on the mount. It is a powered USB3 hub, that unless you are simultaneosly running other cameras, equipment, would do the trick. Just another option. |
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| Thanks David, seems a bit cheaper too 😉 |
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Planetary capture, assuming sufficient RAM for buffering and/or fast storage, is ideally bus limited (esp lunar, with bigger ROI). USB3 on ASI cameras is 4800Mbps (no 10Gbps yet). Dropping to USB2 slashes that 480Mbps - a 10x reduction. On top of that, the protocol for USB3 is more efficient, allowing for more of that bandwidth to be used for actual data instead of command and control overhead. So realistically I think you may be looking at a factor of about 12 in performance drop. Forget about wireless (for the data transfer), it doesn't come even close, especially in real world circumstances. It's really worth the effort to get a working USB3 connection to the camera. Ideally a direct connection - hubs can be bad news if there's "chatty" devices (like USB-to-serial links - very common in astro) on the hub. A small form factor PC (Intel NUC or similar) mounted on your telescope pier or under your tripod which you can admin remotely (RDP/Teamviewer/NoMachine) is great for this. |
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Thanks for the explanation Benny, very clear 👍 I last did any planetary about 10 years ago with a DMK mono camera and filters so a lot has changed since then! My permanent setup is all USB 2 so I think some investment is needed to bring everything to USB 3 which will pay off when I upgrade my CCD camera too. |
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I have no issue with the right hubs. I think the problem people have with hubs is that they don't power it and use cheaper hubs from consumer electronics stores. I use to have troubles with those hubs (multiple brands) Now, I use (so called 'industrial') hubs from StarTech, Gearmo or the Kendrick hub. Ensure you give those hubs enough power (ie. cable should be thick and short enough so no voltage drop at the hub) You also should use quality cables such as those from L-com. Cables such as those flat USB3 cables supplied with ZWO cameras etc. should be avoided. Go for cables up to 3 metres for faster speeds and not the 5 metre USB3 cables. Also, don't exceed the max number of hubs in a run. Keep in mind an "active" cable is just two normal cables with a hub to join them. That hub also needs to be able to draw power from it's source and laptops often can't supply enough current. Also, those 'active' cables often err for multiples of 5 metre sections which doesn't help the faster USB3 speeds Also keep in mind a cheaper laptop might have an internal hub to give extra ports. USBTREEVIEW (windows) is your friend for checking out your USB topology I put together some info on serial links (ie. S in USB is serial) last year at the start of COVID lockdown http://www.astrophotosite.com/tiki-index.php?page=Serial_interface |
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| Thanks Greg for the details and links. I have always bought Lindy USB cables which are high quality and have always been reliable. The ability to use a quality hub will help me considerably, I may be able to shorten the 5m leg to the desktop PC down to 3m so I’ll have a look at doing that. Searching more I have come across a few hits for people using good 5m cables reliably with the Asi462 camera but no details on performance 🙄 |
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I couldn't agree more with what with your comments Greg, and thanks for the links. For deep sky (ASI6200MM) or planetary ASI652MC, I run two USB cables from different ports on my NUC - one runs a hub for all ancilliary devices, and one dedicated to the imaging camera, both high quality 6ft cables. I think my alternative would be to use an "industrial grade" (not consumer grade) hub. Even better than a hub would be to keep the cables short by putting a mini-pc or raspberry pi type device either on, or below the mount - then remote desktop (pc) or link into the app (raspberry pi) via a laptop and control remotely. It's just that todays ultra-fast, ultra-high resolution, sensitive cameras generate sooo much data traffic. Cheers, Dave |
