Telescope Reviews: A real newbie question....

Hi Pete,

I will take a shot at this and others will probably add their opinions. If you are an experienced visual observer you know that most of the time planetary observing is a matter of waiting for brief moments of clarity. With experience you catch these glimpses and your mind composes them into an image that represents the best of those moments of clarity, and can even call upon past experiences to help form a sharp image. That's sort of like what happens with webcam planetary imaging. A good, sensitive webcam can acquire 30 or more images of Jupiter, for example, every second and save them as a video file. Typically at least 90% of these individual frames will be blurred, but among them may be a handful of clear frames that you can extract and stack together to produce a sharp composite.

An experienced visualy observer can probably see at least as much detail on the major planets as can be captured by amateur astrophotographers, so I wouldn't say that electronic imaging can outdo visual, but it has other advantages, like the ability to print and share what you see, and with a good composite image and digital enhancement you can "zoom in" to create an image scale that's hard to duplicate with visual observing.

The Philips SPC 900NC webcam seems to be the favorite now for planetary astrophotography, due to it's very good low-light sensitivity and the relative ease of modifying it for astrophotography. I read this morning in another thread here on CN that Philips may have discontinued it - hopefully if this is true they (or some other manufacturer) will come out with another model just as good for our purposes.

Your Digital Rebel has some limitations compared to webcams that will make it less useful. First, the pixel resolution is lower than that of the SPC 900NC. Even though it's only 640x480 pixels, the SPC 900NC has smaller pixels than the Digital Rebel, which means you get more pixels across the disk of planetary objects, thus higher resolution.

Also, the mechanical shutter of DSLR's is a hindrance for planetary imaging. There's no way you can get 30 frames per second with your Digital Rebel, and unfortunately the shutter is the weakest part of most DSLR's. If you were to take 1,000 frames per night for a month or two with your Digital Rebel you would probably need a new shutter.

Cheers,

--------------------
Don
----------
Atlas EQ-G
Orion 8" f/4.9 newtonian
Orion 127mm Mak-Cass
Orion Skyview Pro mount
Orion 80mm guide scope
Canon Digital Rebel XT
Meade DSI
Philips SPC 900 NC webcam