ASIAir video fps internal storage vs SD card

You just inspired me to run a bit of a test with the hardware at hand to check peak rates. 

ASIAir Plus 256 eMMC, Samsung USB 3.1 thumb drive, and SanDisk 4TB SSD I captured against three different cameras at 1920x1080. The asi2600mc ran at 14.1fps, the asi174mm (USB3) ran between 25fps and 55fps, and the asi174mm (USB2) ran around 15fps on all three drives. There were marginal differences in rates, between each media type... but none of it was decision making, and there wasn't really a pattern.  The eMMC probably held the most consistent rate, but it was slower than the USB 3.1 thumb drive most of the time. The message here is use the format you find easiest when you aren't doing video... for me it will be the thumb drive as it's light, packs easy and is easy to plug into my computer to strip off.  Also, don't do video capture to the ASI Air.

I then took all three cameras to FireCapture on my MacBook. Each camera was able to get close to its peak rate, though admittedly it becomes clear that the peak rate requires some particular settings to get close. The only camera you should really use for these higher rate captures is the asi174mm USB3, so let's ignore the others.

There is a 'high speed mode', that needs to be found in a sub menu... no idea what this does (30-40fps difference in speed), but it probably means you are sacrificing something or it would be on by default. You cannot be in full 16bit mode to hit these rates, but it's not clear that FireCapture moves to 10bit... it doesn't say that explicitly. You must be less than 6ms to get 160fps, so you will probably be at 6ms to 10ms(which would drop your frame rate to 100fps). Depending on what you are doing you will likely use a heap of gain, and perhaps increase your exposure rate and accept dropping your peak frame rate. Depending on what you are doing you won't want to capture for more than 60 seconds, as there will be motion in your subject, but 60 second @ 100fps means 6000 frames, which is probably more than you need anyway, so you might find a balance closer to gain of 300, 70fps and a 45 second capture. The message here... use your computer to record video for astro things (Solar, Lunar, Planetary), and don't expect to get peak rate anyway as its not only about peak rate.

Also... most of these cameras will exceed their peak frame rate if you do an ROI, so if you don't need/want the whole frame, definitely crop down the frame and make use of that bonus bandwidth. If you need the exposure length for a decent image it will cap your peak rate, so you might actually get to go back and crank up that bit rate, which could make a real difference... so again, peak rate isn't everything.