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Hello, I've noticed that the downtime between exposures is considerably longer than expected. I timed how long it takes the ASIair Mini to take a series of dark frames with the ASI6200MM without any other equipment connected. I subtracted the total exposure time from the total time taken. The time between frames is approximately 9 seconds. I have the interval set to zero. The expected behavior would be for the camera to take a shot and then send the image file to storage/tablet from the buffer while starting the next frame. What seems to happen is that the camera takes a sub, transfers the sub to the ASIair, waits for something (maybe for the ASIair to transmit the frame to the tablet), and then starts a new sub. This isn't such a big deal when doing 5 minute NB subs but, when doing 30 second L subs, it can really add up. Can this time be reduced? If so, how? Thanks! |
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I don't have a lot of experiences with ASI air so far but isn't that the dither settling time of the Guidescope ? So that it only starts the exposure as soon as the mount is stable again? |
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Jens: Good thought, but I had everything except the camera disconnected from the ASIair. |
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if you look at the driver source code, it calls grabImage as the last step in the function that takes an exposure. Meaning it will not start another exposure until the image has been transferred to the computer. I believe the video mode operates the way you are expecting but at 16bit full res that could prove too indigestible for the USB 2.0 link, let alone on a single board computer that writes on an SD. https://github.com/indilib/indi-3rdparty/blob/master/indi-asi/asi_base.cpp |
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if you look at the driver source code, it calls grabImage as the last step in the function that takes an exposure. Meaning it will not start another exposure until the image has been transferred to the computer. I believe the video mode operates the way you are expecting but at 16bit full res that could prove too indigestible for the USB 2.0 link, let alone on a single board computer that writes on an SD. Thanks! It seems I need to upgrade to the AsiAir Pro or a mini PC. Any recommendations? |
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| Interesting. I can see that would be frustrating. On the larger ASIair Plus there is no noticeable delay between exposures. The scope's wifi takes 8 seconds to load a frame onto my tablet, but the unit keeps shooting during the transfer, too. |
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| I will second @Dave Rust 's comment above. As a user of the ASIair Pro and now the Plus model, I have experienced no delay between any exposures. And, with respect to dithering, if your PA is good (to me, less than 30" total) and guiding stable, the delay is only a few seconds. |
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| I hadn’t thought about the dither issue Jay mentions. I do have one mount that doesn’t settle well after a dither move. It sometimes takes 5 minutes to realign so the camera can resume shooting. That would indeed explain a long delay between shots, in which case the ASIAIR would be operating correctly. |
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| I ran my 6200MM in APS-C mode last night to see what would happen. The time between shots dropped from 9s to 4.5s. This test was with the camera only so no dithering/setting time included. |
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Jon, these are your two bottlenecks: USB 2.0: At 480mbps (theoretical, likely closer to 400mbps) your 121 megabyte files take 2-3 seconds just to stream over the wire. SD Card: Most of the cheaper standard-speed SD cards are quite slow, 12 MB/sec. This is likely the majority of your delay. You can't do anything about the USB 2.0 limit without upgrading to a new ASIAir with USB 3. The SD card write speed you may be able to improve by upgrading to a high-speed card, but this is a pain (you need to clone the old card to the new one) and is unlikely to provide much more speed. Since USB 2.0 is faster than the built-in SD card, you could use one of your USB ports to hook up an external SSD drive. A high-speed thumb drive may work, but I find the external Sandisk SSD drives to be wonderful. Note, I do not have an ASIAir but have lots of experience with the Raspberry Pi 3/4 models on which it was based. I run NINA, so I use MiniPCs at each of my mounts and connect over Remote Desktop. Bee-Link U59s with the N5105 processors are a wonderful fit; they can run off 12V (such as from a Pegasus Astro PowerBox Advance), they're fast enough to run higher-end acquisition software, the built-in m2.2280 SSD drive is blazing fast for astro, and you can add an additional 2.5" SATA SSD for extra storage. The 8GB RAM/500GB SSD option is a shocking $120 now on Amazon. Note: With any SSD, never fill it up over 80% full. You need to give the wear-leveling algorithms room to work; leaving a small amount of space free on an SSD rotating through large astro files is an easy way to burn out those cells. Hope this helps! |
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Jon, these are your two bottlenecks: This all makes sense. I did an experiment last night where I ran the 6200MM in APS-C mode and the delay between shots dropped from 9s to 4.5s. I've been looking at https://www.amazon.com/MeLE-Quieter3C-Computer-Industrial-Ethernet/dp/B0BYZ91RFL/ as a possible mini PC. I like that it is a fanless design and accepts USB as a power supply. Also the half gig internal SSD (EDIT 2: It's half eMMC and half SSD.) and 16GB RAM seem nice. As with any PC, of course, stats don't matter much if any of the components are cheap and create a bottleneck. |
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I don't have any experience with fanless MiniPCs, other than knowing a few people in the club that use them. I wouldn't consider them personally because their CPU power is just too limited and they're generally not very upgradeable. While ASIAir can run comfortably on the Raspberry Pi, the KStars/Ekos you'd likely run on the MeLE might be resource-challenged. And if you move to something like N.I.N.A., you're going to be instantly tempted to start using some of the awesome plugins -- which often add to the system resource load (CPU, specifically). To give you an example, I ran 5 U59 MiniPCs on my various rigs. My RASA, however, took images so fast that the PC would spend most of its time doing star analysis to determine the HFR of each image. And if I tried to use anything like Hocus Focuses's Aberration Inspector, it literally couldn't keep up with the subs and would eventually crash. This is an extreme example, because the RASA is 24.5 times faster than the EdgeHD 14.... but you get the point. Get a slower machine and everything will be slow, and even if those slowdowns are only .5 second per operation, those operations really add up. I upgraded my U59 on the RASA and I was amazed at how much faster platesolving, focusing, etc. was. Things that I didn't think were slow were really slow by comparison. I don't run these MiniPCs on the scope itself, so I don't need to worry about vibrations... but I can't imagine these smooth-running fans causing any problems at all. All mine are perfect, and after running for 2 years out in the desert, when I opened one up last month, it was totally clean inside. One word of warning for USB-powered machines... USB is not able to deliver much current. I'm convinced that some of the "USB disconnect" and "network disconnect" issues people sometimes complain about with these machines occur when the machine is under load and exceeds the current USB can deliver. Even my Raspberry PIs, which I used to power via USB C, are now powered by dedicated power supplies. |
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I have an ASI2600 DUO and there's no question you will need a fast laptop with an internal SSD if you are looking at short frame rates. For example, on some bright targets I used 100 x 4-second frames at its full resolution, and yes I agree you would not want to wait 9 secs per frame. OTOH if your exposures are a minute or more, 9 seconds is not particularly relevant. The ASIAir uses an SD card, which is s.l.o.w. SSD would be a lot faster. In comparison my 2020 Intel MacBook Air can manage 3fps from an ASI2600 DUO - at the full resolution - while my wife's newer M1 Air is significantly faster again. NB I have just bought and ASIAir Plus specifically an all-in-one solution for polar alignment, auto-guiding and EAA. If I was trying to do something really demanding I'd still hook up the laptop to the ASI2600. And yes I'm inclined to see if my ASIAir Plus can use an external SSD as I have a spare one lying around. |
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I don't have any experience with fanless MiniPCs, other than knowing a few people in the club that use them. I wouldn't consider them personally because their CPU power is just too limited and they're generally not very upgradeable. While ASIAir can run comfortably on the Raspberry Pi, the KStars/Ekos you'd likely run on the MeLE might be resource-challenged. And if you move to something like N.I.N.A., you're going to be instantly tempted to start using some of the awesome plugins -- which often add to the system resource load (CPU, specifically). I think I see what you are getting at. Even though hypothetically the CPU in a fanless unit can keep up with demand the reality is that the CPU is throttled to prevent overheating, thus drastically reducing performance. I presume you are talking about: https://www.amazon.com/dp/B09J4D6TMG Looks like I missed the $120 deal on the 8gb RAM version so I might as well go for the 16gb version for just a few bucks more. Looks like USB power isn't an issue for me since I have 12v DC power available on my mount's dovetail. |
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No doubt -- even a Raspberry Pi 4B will thermal-throttle itself. It's inescapable if you DON'T buy a case with a fan, but happens frequently with the fan as well. The one fanless option I'd consider would be ARM processors -- if Windows ARM was more stable and if more of our astro software was either natively-compiled or available in x64 with an ARM64EC build. But, it's piecemeal. The reason I'd consider it is because of my experience with ARM processors in the cloud but especially because of the amazing performance-per-watt of Apple Silicon -- I'm blown away how I can crank through a huge stack for 6 hours and barely even hear the fans on my M2 Max in my MacBook Pro. Even running Windows 11 Arm in Parallels on the Mac is just crazy fast. The 8GB version is there at only $109 now with the $60 off coupon -- look for the checkbox. LOL, prices fluctuate hourly. But before you buy, do a bit more research rather than just following my suggestion. Bee-Link has a huge number of different versions available, some of which are not on Amazon and some of which are on Amazon but not their website. I swear, they release new models 10 times a year, but almost all the new ones are 19V instead of 12V (I had to reach out to them directly to ask, since it's rarely specified on Amazon or their website). I'd recommend not going with one with a discreet graphics card (AMD, etc) if you live in a hot climate, run off battery or if you run long focal lengths -- they generate a lot of heat. Also, consider whether you want to jump to a larger imaging suite. ASIAir is awesomely simple, so an ASIAir Pro may be a great option. Increased functionality means increased complexity. Good luck & have fun! |
