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Re: (meteorobs) Hello all
Hi All!!
It has taken me a while to respond to the several thoughtful comments in
reply to Cary's earlier Hello all message which essentially came from both
of us. I now have a few nights observing under my belt with this STAR
Lite-1 Image Intensifier system and we have posted some of the new clips,
several of them being apparent Perseids, on our Web site at
http://www.scitechastro.com/, along with some new remarks about some meteor
observing aspects of the system, etc.
Yes, the FOV is small, but actually the useful area is probably more like
10 degrees than the 5 degrees that we mentioned as being in best possible
focus. The optical experiments I have been able to do on the system
indicate that although there is some fall-off in resolution in the optical
system at the edges of the field, most of the fall-off is due to the
electrostatic focusing of the (remarkably high gain) Gen I intensifier.
This is a small Russian intensifier, and quite frankly I don't have all the
data on it re size of the effective active photocathode area. Regarding
the 15000x gain, (note that this is not the 1500x gain of many GenI IR
image converters, but real image intensification), even though higher gains
are available in GenII systems, this is enough to produce scintillation
noise, characteristic of image intensifiers, in the recorded image data.
This means that the image optical coupling efficiency is high enough to
record effectively all of the useful signal. This seems pretty remarkable
to me, but of course I am comparing with the old GenI tubes of the '80's
that didn't even come close to this kind of performance. I never could
afford a GenII tube myself, let alone a GenIII, but these type systems are
available now for about $2000 without the CCD, and a person can easily
spend more than $5000 on an intensified CCD camera. We will be looking
towards offering a higher-end system in the near future for discriminating
users. Having used image intensifiers in my own research over the years (I
used an RCA-Carnegie 2-stage image intensifier in the observing system I
put together to get the observations I used to make the color images
illustrated in The Color Atlas of Galaxies - Cambridge University Press,
1988), I was just amazed at the performance-per-dollar aspect of this
little system. It was probably premature of us to offer this system
almost immediately upon putting it together as we have, but we felt that we
saw some real value in it for meteors and that we ought to make it
available to someone who might like to have this capability for this year's
Perseids, which were already nearly upon us. Anyway, you may be interested
to check out a few (6) of the more than 70 .avi files I have pulled out of
3 1/2 hours of video that I have had a chance to run through the computer
system, out of the more than 12 hours of video that we have taken over
three nights (0804,0805,and 0807) so far. It would be nice to automate
some of this for sure, but it is possible with current off-the-shelf
software and inexpensive video capture cards to acquire, and process to a
modest (but certainly useful) level of information quality, qualitative to
semi-quantitative data on meteors with this system even now. Please take a
look and see what you think..
http://www.scitechastro.com/ and click on the Image Intensifier menu item.
We welcome any comments or suggestions anyone may have regarding any aspect
of this.
Thanks and
All Best Wishes
James Wray
----------------------
At 09:59 PM 8/5/99 -1000, you wrote:
>Sirko has pre-empted most of what I was going to say or ask.
>
>First I welcome another supplier of integrated low-light video systems
>which have applications in meteor observation.
>
>15,000x amplification sounds low. 30,000-50,000x amplification sounds
>more normal. Some of us are interested in the faint meteors too, so a
>small field is less of a problem, but even so 5 degrees is too small
>for mag 8. An even response across 15 degrees might just do, but it's
>tight.
>
>For many meteor folk they would want to see several constellations in
>the field to record visual meteors with a wider field is likely to sell
>more than the current configuration. The ability to interchange lenses
>for varying field diameters and limiting magnitudes is desirable.
>
>The restricted field of view means many meteors will start and/or
>leave the field of view. What's the distortion like? With a small
>field there are fewer stars to determine the astrometry, and hence
>radiant determinations are poorer. Relatively longer paths reduce
>orientation errors too.
>
>What's the diameter of the image intensifier phosphor?
>
>> PS: I'll be off now for the solar eclipse and the Perseids until August
>> 24, so I will not be able to continue this thread until then.
>
>Aug.24! We had the early Perseid thread again this year. Is Sirko
>looking for the latest Perseid?
>
>Malcolm
>
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>
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