(meteorobs) Improving the contrast of all-sky camera &mirrorsystems. Chris?

[Larry]

Hello Leo.

It seems you are pursuing very challenging work in daylight lightning.

There is a possibility that very large(not small) industrial IR domes where 
the camera is distant from the surface of the dome itself at the radius 
center might work for that. Those domes are used in Casino's but are a bit 
"pricey".

This would allow more latitude in sensitivity and threshold adjustment. I 
lost a daylight fireball test camera using this method due to internal metal 
or PVC sweating even though it was heated on a timer during the night and 
was sealed from ambient moisture. The CCD substrate itself failed I believe 
because slow oven treatment did not bring it back.

If you can post some lightning strikes or your personal research results I 
think it would be quite interesting to the group. Certainly I would like to 
see what you can image.

Yes on the mechanical shielding. I will study that issue now. I do need to 
keep certain fixed lights on my horizon as Azimuth alignment markers, which 
assures me no changes have occured with the cameras North alignment during 
my routine servicing.

YCSentinel




----- Original Message ----- 
From: "Leo S" <l.stachowicz at btinternet.com>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: 2009/06/15 19:41
Subject: Re: (meteorobs) Improving the contrast of all-sky camera 
&mirrorsystems. Chris?


I'd be inclined to agree also. some kind of hood or shield would be
good. Perhaps a dustbin lid or satellite dish? :)

The other things that I have learned from trying to photograph daytime
lightning would be to decrease exposure time of each frame if you can
and/or block some light with a filter or polarizer, although this
decreases overall sensitivity and increases the threshold at which light
will register, but providing the event is relitively bright compared to
the background sky, contrast should increase.

Leo



Larry wrote:
> Chris,
> Your mechanical shield or a full skirt may be what I will wind up with 
> too.
> I have a particularly bad occasional situation which needs resolving on 
> pool
> lights next door which are 7 or 8 feet below my camera lens. I am not sure
> how close it is to being direct lighting and how far below true horizon 
> they
> are located. Those lights and other luminous points are well illustrated 
> in
> a fireball shot at:
>  http://cams.seti.org/sentinel/v20090326_210854.18.jpg
> I do not want to do anything about these lights until my measures are
> completed.
>
> Finished the transit work today and will start gathering information
> (measures) on exactly how far from the Sentinel image circular edges true
> horizon is located when the camera is properly aligned to zenith and has a
> very minimal amount of clipping (but equal) in the North & South 
> direction.
> Hopefully that clipping will not be above true horizon.
>
> Below true horizon measures will be taken with a precision digital level
> mounted on the transit aimed at objects at the circular edge of Sentinel
> photographs in a daylight shot.
>
> That info. will help make reporting to AMS a bit more accurate and give
> others decent reference points too on their Sentinel photographs for true
> horizon and below.
>
> Sunlight & contrast is the secondary objective. Any gain in that is worth
> the effort.
>
> Hemispherical mirrors will be considerably more difficult to measure. They
> can see far below the horizon I noticed before during some tests. My 
> mirror
> system is down for modifications at present.
>
> YCSentinel
>
>
>
> ----- Original Message ----- 
> From: "Chris Peterson" <clp at alumni.caltech.edu>
> To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
> Sent: 2009/06/14 06:35
> Subject: Re: (meteorobs) Improving the contrast of all-sky camera
> &mirrorsystems. Chris?
>
>
> My camera does not capture more than a 180° field. Certainly, the Rainbow
> lens doesn't get you 20° below the true horizon. My actual horizon is a 
> few
> degrees above the true horizon in spots because of hills, but I have not
> found any need to use a physical mask. I have a logical mask in the 
> software
> that prevents false triggers from areas of the image that don't show sky.
>
> One of my cameras is installed at a school in a location where car
> headlights from the parking lot can hit the dome. These lights aren't
> visible to the camera directly, but the light on the dome can generate 
> false
> triggers. I've got a mechanical shield installed in that case to shadow
> those lights. The shield isn't visible in images because it is out of the
> camera's FOV. A shield like this is always useful if you are in a 
> situation
> where you have a significant direct light source hitting your dome.
>
> I start/stop my cameras when the Sun is 6° below the horizon, so I'm not
> concerned with sunlight hitting the dome at sunrise or sunset.
>
> Chris
>
> *****************************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
>
> ----- Original Message ----- 
> From: "Larry" <ycsentinel at att.net>
> To: <meteorobs at meteorobs.org>
> Sent: Sunday, June 14, 2009 12:42 AM
> Subject: (meteorobs) Improving the contrast of all-sky camera &
> mirrorsystems. Chris?
>

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