Astronomy from the couch: Plasma TVs for viewing

[radarredux]

In another thread I wrote: "<i>...a fairly low cost telescope with automated tracking capabilities, integrate a digital camera, use WiFi to link the telescope and camera to the home computer in the den...</i>"<br /><br />And then I had the "doh!" moment.<br /><br />I have a Mac Mini connected to my 50" plasma in the family room -- Maybe I can become a couch potato astronomer!<br /><br />I should connect a computer driven telescope with a firewire (or highspeed USB) connected camera via a T-ring to a local laptop, and then connect the laptop over WiFi to my Mac Mini in the house. Then I can do astronomy from my plasma TV in the comfort of the family room. All I need to do is write the code to let the Mac Mini send control messages and receive data from the laptop in the backyard.<br /><br />Are there already such packages (control the computer that drives the telescope from another computer wirelessly)? If not, are there protocols for these computerized telescopes standardized or at least documented so I can write my own driver?

 

[docm]

The open-source Stellarium package (Windows/Linux/OSX) has added support for certain Meade, Celestron and one Losmandy 'scope. Basically you use it to steer the device using their telescope server software;<br /><br />http://stellarium.org/<br /><br />http://www.stellarium.org/wiki/index.php/Telescope_Compatibility<br /><br />From there it's a matter of feeding the CCD output. If you're using a cheap CCD imager they usually have a standard composite video output (RCA video jack) for display on a TV or USB to a laptop, but true CCD imagers deliver their data to a computer one color filtered image at a time for serial image capture/compositing. <div class="Discussion_UserSignature"> </div>

 

[rocketman5000]

I'm not sure, but if you got such a system up and running could you broadcast, podcast, or stream what you are showing across the net? I read your other idea and thought it held water.

 

[docm]

If you can get images into a computer it's "net-able", the question is what kind of images? <br /><br />Straight composite or econo-USB/CCD video can be treated like a web cam, but has the weakness of being good only for bright objects; moon, filtered sun, the hottie across the quad etc. <img src="/images/icons/wink.gif" /><br /><br />For deep sky you typically capture several to dozens of stills off a CCD imager, either grey scale or with color filters, then composite (blend them into a single image) them in software to build their cumulative intensities & colors into something useful. To stream these images would not be realtime but definitely pod-able. <div class="Discussion_UserSignature"> </div>

 

[rocketman5000]

See now you're just talking crazy talk. I really don't know that much about networking of computers. But composited images that you speak of could refresh every couple of seconds right? While it wouldn't be real time it would still have the feeling of real time in the sense that it is changing as you watch the screen. Having truely real time video would be "cool" if you were in such a location as to see Nortern Lights, rocket launches etc.

 

[docm]

Video is indeed streaming images, mostly exposed for either 1/25 (PAL) or 1/30 (NTSC) of a second. Not much, even for fast film, which is why the "imagers" based on video CCD's are only good for brighter objects. They're also small; often only 1/4 0r 1/3 inch....often adapted lower end camera/camcorder units. This limits their sensitivity.<br /><br />The problem for dim objects is that each images <i>lumance</i> (brightness) is very low due to that short exposure and the relatively low sensitivity of video CCD's, which is why when you video a star with a camcorder you can't see anything. Capture that frame, put it in Photoshop, adjust the gamma and you <i>might</i> see an outline & few details.<br /><br />Still, that video of the moon or Saturn can often be captured in Windows Media Encoder (free download) and encoded to WMV for downloading or fed to webcam software for real time encoding/streaming. <br /><br />Now lets talk a real telescopic imager CCD. First it's more expensive, more sensitive, larger (more area = more photons intercepted) and shoots a longer exposure. Set the 'scope to track, shoot several images in sequence then load them into software and you can stack them, adding their lumances and details to create a much higher quality image; a "composite". <br /><br />Even with for-the-purpose software this takes time, so streaming in real time is out and post-processing poding is in.<br /> <div class="Discussion_UserSignature"> </div>

 

[radarredux]

OK, here is what I am leaning towards right now...<br /><br /><b><font color="yellow">Block 1:</font>/b> iBook controlling a low-end computer controlled telescope and an attached digital camera. My Canon EOS 30D seems pretty capable, including being able to block open the shutter for long exposures, and Apple's Image Capture SDK for controlling digital cameras looks pretty capable too. I am curious as to how far I can push these two elements. As pointed out, there are CCDs specifically for telescopes too.<br /><br /><b><font color="yellow">Block 2:</font>/b> Client-Server design, where the local iBook still controls the telescope (and captures the images), but control is provide by a remote client (e.g., the MacMini attached to the Plasma display inside the warm, comfortable house).<br /><br /><b><font color="yellow">Block 3:</font>/b> 3-tier system where a web server (hosted at ISP) controls the iBook. In this model, a remote user (e.g., anyone from the Internet) logs into the web server, sends commands to the telescope computer via her browser, and recevieves updates in the browser. There will probably be two images: a low-res one updated automatically on the web screen via AJAX and a high-res that can be downloaded with a click. People could schedule for n-minute blocks of time (e.g., 15 minutes), and everyone can watch what someone else is watching.<br /><br />If I can get it working, I will post the full design and code so other people can implement their own version.</b></b></b>