Meteor Camera Sony ExView HAD help sought

Group,

I am interested in brewing an inexpensive all sky meteor camera. In this
regard, I am looking for someone or a set of instructions to cripple the
automatic gain control and automatic brightness control on a Sony ExView
HAD chip.

I think the answer for the "cheap meteor cam" what has been done by the
Croatian Meteor Group.

Report 2nd Year of Croatian meteor network (2009)
http://www.imo.net/imc2009/pdf/segon...ic_imc2009.pdf

Slide 3 Describes using the Sony EX View HAD modified to disable the
automatic gain control to reach down to 3 or 4 mag with modifications.

The Croatian group is using a $270 base camera from Supercircuits based
on the Sony ExView HAD chip -

http://www.supercircuits.com/Securit...Dome-Security-
Cameras/CD42IRHR

I purchased Supercircuits PC402UXP Super Low Light camera board with
this same chip and have been testing it for use as a low-end meteor cam.

http://www.supercircuits.com/Securit...meras/PC402UXP

The Croatian Meteor Group (at http://www.astro.hr/hmm/ ) concluded for
the Sony HAD ExView that the raw Sony ExView might function with the AGC
enabled,

"After many tests of different models, 1004X black-and-white cameras
were chosen for CMN. Their main advantage is availability and low price
(around 60 EUR currently). They are build around well known Sony 1/3"
EXView HAD CCD chip. . . . . The hardware of the camera is slightly
modified in such a way that the video signal gain is fixed to about 90%
of maximal gain. This is done solely to make camera more suitable for
photometry. Camera can be used without this modification also, the only
difference being that variable gain will make accurate trail photometry
impossible in most cases. The trails itself will be recorded without any
problems.Using an unmodified camera is a good option if one is not able
to perform the required modification, or to find someone who could do
it. The modification itself is not difficult, but requires some
soldering experience and a good solder iron as components on camera
electronic board are tiny indeed."

http://www.astro.hr/hmm/

In testing, I found the automatic gain control really reduced how deep
the camera board could see.

Having little background in electronics (I'm on a basic soldering level
and have done a couple of the old Forest Mims Radio Shack projects),
does anyone have a buy-the-numbers instruction sheet for how to modify
the Sony ExView HAD chip (specifically the Supercircuits PC402UXP board)
to disable the AGC and/or the auto brightness control?

Thanks, Kurt - Canopus56

On Sun, 20 Dec 2009 04:58:33 GMT, canopus56
wrote:

I think the answer for the "cheap meteor cam" what has been done by the
Croatian Meteor Group...

I'm surprised you're seeing any effect from the AGC. I use a PC164C,
which has (last time I checked) the same chipset as the PC402. I have
found that the AGC makes no difference at all for meteor work. The AGC
works by looking at the total illumination level, and even the full Moon
or a bright fireball isn't enough to cause the gain to be reduced from
its maximum. There must be something odd about the PC402 board I don't
understand. Have you considered using a PC164C? You can turn off its
AGC.

Keep in mind that the mag 3-4 level they are reaching is because they
aren't operating an allsky camera. Their lens is too long a focal
length, so they are only seeing a small patch of sky, allowing them to
get deeper. They are also getting that sensitivity after frame
integration, which means their limiting magnitude for meteors is quite a
bit dimmer than that for stars. If you want allsky coverage, your
sensitivity will be around mag 1 for meteors.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote in
:
snip
I'm surprised you're seeing any effect from the AGC. I use a PC164C,
which has (last time I checked) the same chipset as the PC402. I have
found that the AGC makes no difference at all for meteor work. The AGC
works by looking at the total illumination level, and even the full
Moon or a bright fireball isn't enough to cause the gain to be
reduced from its maximum. There must be something odd about
the PC402 board I don't understand. Have you considered
using a PC164C? You can turn off its AGC. snip

Chris, As always thanks for the tips from the voice of experience. - Clear
Skies - Kurt

Chris L Peterson wrote in
:

snip
Have you considered using a PC164C? You can turn off its
AGC.

Chris, there is a switch? I haven't physically seen a PC164C. The product
literature does not list it as AGC configurable. I have a friend who has
one and he did not indicate that there was a switch to turn AGC off and on.

Thanks - Kurt

A webpage on a modification test
http://www.saao.ac.za/~wpk/1004x/index.html