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Re: (meteorobs) Lew's video meteor system
A few more comments on video systems...
Pete wrote:
> wary of. The first is the f-stop on the lens you plan to get. You want to
> have the fastest possible lens you can afford for a given field of view.
> The lens should also be well corrected so that the image is not severly
> distorted in the corners of the image. Both features come with a price tag
> but shopping around used camera stores sometimes turns up a decent buy.
The first thing is obvious - the faster your lens, the better your
limiting magnitude. However, this holds only up to a certain point. For
example, our ultra-fast f/0.75 Rayxar lenses are *so* fast, that the image
intensifier is complete saturated under normal conditions. Only when
observing under really dark skies I can use the full intensifier gain.
Under moderate observing conditions a faster lens is still the better
choice, as with decreasing MCP gain you also reduce the noise.
As for image distortion I don't see any problems. Usually you will use
some photo lens, which all work very well. Both the distortion of the lens
and of the image intensifier has to be considered during the reduction of
meteor images, anyway.
> What are the details on the rest of the imaging system? Is the intensifier
> tube 1st, 2nd or 3rd generation (big difference in noise characteristics).
> Can you adjust the intensifier gain to deal with different background
> illumination (dark skies, light pollution, bright moon conditions)?
2nd generation intensifiers are certainly the best choice. Controlling
the gain is really important (see above), but I guess that most
intensifiers have this feature.
> Are you
> getting a low light black/white CCD? Is the CCD output frame rate NTSC or
> is it an integrating camera (Lew is in the USA for those PAL afficiondos).
I made the experience, that also every CCD video camera can be used in
connection with an image intensifier.
> These are just a few questions one might inquire into before buying a
> system. Both myself and Sirko have written some articles on video meteor
> issues in back iussues of WGN that you may want to peruse.
In addition you find also some information on our web site at
http://www.imodot net/imo, as you know.
Sirko
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