Tuesday, October 28, 2008
DMK 21AU04.AS with Asus Eee PC
I got a chance to try out an Asus Eee PC 900 which has an Intel 900MHz CPU, 1G memory as well as 16G SSD storage. Since it is so small and portable like my aging Sony Vaio U3, I wonder if it is a good computer for field usages as an amateur astronomer. Therefore, I pulled out my DMK 21AU04.AS to try out its performance.
The Asus Eee PC is a great success. I believe that it is so attractive because of its price, portability and performance. It has created a new class of computing device which people now call it a netbook. Of course, with a fully functional operating system like Linux or Windows XP, you can do a lot more than web browsing and checking your email box.
The model which I had tried is selling at $3xxx HKD (i.e. around $400 USD) and so it's very attractive indeed. It has three USB 2.0 ports so that you can hook your camera to it, be it a cooled CCD, or a ToUCam Pro, Meade DSI, Lumenera or TIS DMK/DBK/DFK. You can also use it for guiding camera, and you still have one or two ports left for devices like Shoestring GPUSB and to control your mount.
While the built-in battery is decent, but it is by no means enough for a whole night of usage. And here comes another attractive thing for amateur astronomer... it accepts 12V power input, and that's simply great. You can directly use your Sealed Lead Acid battery without any transformer, that means portability and it is also very energy efficient.
For guiding purpose, there should be no problem since you can install Windows XP to it, and many popular software will work like PHD guiding, etc. The USB bandwidth requirement is no big deal for guiding.
What interest me most for this test is those bandwidth hungry equipments, like a fast frame rate camera. The CPU of these netbooks is not fast in today's standard, and the SSD is not very fast as well. In my test, I used 640x480 which is the highest for my DMK 21AU04.AS, and I can get as high as 25 fps. And this is also the fastest frame rate that we can get with this setup. Using software ROI of IC Capture will not help for this kind of slow CPU, for the extra CPU cycle required for cropping will further degrade the frame rate.
So, given a 60 fps camera, is 25 fps enough?
Yes, I would say.
For planet imaging, you cannot use shutter faster than around 1/30s unless you are using sub-optimal sampling. For most of the time when I use my scope at f/20, f/30 or even slower, 1/15s with moderate to high gain will be the most appropriate, that implies that you can use 15 fps at most. So, the Asus Eee can do it.
For solar imaging, if we are targeting surface detail, we can easily go faster than 1/60s (actually, 1/500s is not uncommon), and so you can still get 25 fps at most. This left something to be desired, but it's still use-able, not too bad. If we're targeting prominence, we will use as slow as 1/30s or even slower shutter, in that case, the Asus Eee can do without problem.
Finally, if you're using slower ToUCam Pro which you will use 10 fps for most of the time due to the compression, the Asus Eee can deliver what you needed, and there's nothing to give up.
However, since I already got my Sony Vaio U3, I will not buy an Asus Eee at the time being, and my work horse camera is a DMK 31AF03.AS which can give 1024x768x30 fps and thus the Asus Eee is clearly insufficient, not to say that it lacks a 1394 port. My notebook hunting continues...