[AZ-Observing] Re: The Web Cam
- From: PHXJeff@xxxxxxx
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 9 Jan 2003 13:46:26 EST
Wil Milan replied in part:
>There are several reasons why specialized astro CCD cameras are expensive
Many many years ago when I was working my way through college I worked
nights at a General Electric receiver plant. My job was to troubleshoot
the factory line AM/FM receivers that did not work. At first I was
appalled at the transistors they used for the parts. They purchased
buckets (literally pails) of reject transistors (many different types)
from Texas Instrument. These were put into the units and tested.
Surprisingly a high percentage of the received worked fine with the
rejected parts.
The CCD chip is a very complex device. I suspect the top of the line
expensive cameras use chips that have passed far more tests than the
cheaper units. Even though they may all have the same part number and
basically function the same, there are probably many levels of quality.
The web camera use normally does not need the high quality chips. When
using these chips for astronomical observing, the quality become more
important, however.
What is most interesting is the ability to take astro images with the
cheap camera that sometimes rival those taken with units orders of
magnitude more expensive. In fact, if anyone wishes to use these cheap
web cams for astro photography I think just doing two things can greatly
enhance the results. Figure a way to subtract a dark frame (this is is
mainly a software problem and will cancel out many of the cheaper
device's flaws) and find a way to cool the camera (this will reduce the
noise and increase the sensitivity considerably).
While this topic may not be 100% about observing, it certainly has direct
bearing on a method of observing that previously was available only to
professionals and those willing to shell out thousands of dollars.
Jeff
Jeff Hopkins
HPO SOFT
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