Note: This page is under construction.

I'm trying to figure out a way to use the Apple iSight camera for video astronomy. It's a very nice camera, with an f/2.8 autofocusing lens, and is connected to the Mac via FireWire (IEEE1394). It's fully controllable through the QuickTime VDIG interface.

I believe this camera could be very useful for video astronomy. There are several challenges to getting it working, however: (1) it runs quite hot, which might make it susceptible to low-level noise in dark situations, and (2) mounting it to the telescope while keeping it cool is a problem I have yet to solve. I have a number of ideas, but haven't had time to explore them yet.

Capturing video with the iSight can be done via the QuickTime Broadcaster software, available for free from Apple.

A nice article on using QuickTime Broadcaster to capture video from the iSight is available on MacDevCenter:

Keith's Image Stacker can be used to import QuickTime files and process them for astrophotography. It's shareware (pay the guy if you use it... he works at my alma mater, the University of New Mexico).

ADAPTER CONCEPT

Looking through the web sites where digital camera adapters are sold, I came across the Uni-T™ adapter from ScopeTronix. I already own a Digadapt™ afocal coupler for use with my LX90, and I liked the build quality, so I decided to buy the Uni-T connector, thinking it would be useful for holding the iSight in place above the camera adapter.

I think I should also put a soft rubber gasket or O-ring around the base of the iSight once it is in place to act as a light stop. This will prevent stray light from the outside from getting into the stack and ruining shots, but more importantly, it will nullify the tiny green LED that's embedded in the top of the iSight camera body. This light is normally lit when the iSight camera is active.

Unfortunately, I neglected to pay attention to the threading on the adapter. It's male. And so is the threading for the T-ring that normally goes on the end of the Digadapt connector. Now I have to find a female-to-female T-thread coupler ring to connect the two adapters. It mustn't be too long, or the iSight's FireWire cable will run up against the Uni-T ring, requiring a bit of metal surgery to make everything fit together properly. I don't think it's going to be necessary, since the Digadapt outer sleeve can be adjusted to fit the eyepiece snugly.

Below is the concept diagram (Adobe Illustrator 10 is my friend):

A helpful fellow named David Watson on the Yahoo! LX90 group suggested that I remove the female-threaded ring from a camera T-ring adapter and use it to connect the Uni-T and the Digadapt. This ring is very small, and will hold onto each component in the stack by only a few threads, but it should be more than sufficient for this lightweight application. Thanks, David!

I removed a female-threaded ring from the Minolta T-ring adapter I had handy, and assembled the stack. Here's a photo:

As you can see, the Digadapt connector has seen some use. The thumbscrews on the Uni-T adapter had to be backed out almost all the way to the end of their travel, but they hold the iSight camera with gentle firmness. The fact that the thumbscrews are plastic is a boon: they won't mar the finish on the camera.

Here's a picture of the Orion Short Tube 80 with the adapter hooked up inline. (It's on a video camera tripod, connected by the 1/4 20 connector. I decided to try the camera out during the day just to make sure it was possible to get a decent image.

I tried to use the QuickTime Broadcaster software to capture video from the camera, but it turned out to be a bust. I was able to use it to get a rough idea of the focusability of the camera when hooked up through the image erecting prism. It wasn't. I pulled out the erecting prism and connected it inline, and with the Digadapt connector slightly pulled out I was able to get a decent focus. But the QuickTime Broadcaster (for some reason) wouldn't capture at a decent frame rate, and for another inexplicable reason it kept resetting the focus mode to automatic, which naturally defocused the image. Bah. After about an hour I gave up and started to look for alternatives.

Fortunately, the O'Reilly web page where I first read about using QuickTime Broadcaster had an even better suggestion: the tiny program HackTV Carbon, which is a bare-bones VDIG controller and QuickTime capture program. PERFECT! Unlike QuickTime Broadcaster, it has a resizable preview window, making it much easier to use outdoors, and it captures both audio and video at very high frame rates without completely annihilating the wimpy CPU on my 400 MHz PowerBook G4. In fact, after I shut off the audio I'm pretty sure I got up to thirty frames a second at 640 x 480, which should be more than adequate. The image quality is quite good for an inexpensive camera.

Below is a sample frame from a movie I captured, showing the hillside above my house. There's is some vignetting from the 25 mm Plössl eyepiece (which yields a magnification of 16x in the 400 mm f/5 ST80. Not too bad! Lots of heat shimmer visible in the movie, and this is about as good as I could get with the focus today. This is the raw image size, but I've converted it to a medium-resolution JPEG for the web, so it's not quite as detailed as it looks on my machine. Sorry.

And below is a frame showing a summed stack of 595 frames from the same QuickTime movie. (FYI, the movie lasted 22.18 seconds, and averaged 26.71 frames per second at 640 x 480 pixels. It was captured in component video format, CCIR-601 uyvy, millions of colors.) There is some image enhancement, but since the image was basically about as well focused as it was going to get, and there was quite a bit of heat shimmer across the intervening ground, the enhancement isn't too obvious.

Now I just have to figure out what all the interesting commands in Keith's Image Stacker do. And try it at night. That will be the acid test.