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

[Larry]

Kindly avoid further personal communication.

Thankyou.
YCSentinel

----- Original Message ----- 
From: "Jim Gamble" <jagamble at sbcglobal.net>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: 2009/06/13 23:56
Subject: Re: (meteorobs) Improving the contrast of all-sky camera & 
mirrorsystems. Chris?


Larry,
Since you're not seeing the system for it's benifits, one of which is that 
it was free of charge to you, the second of of which is that it does what 
it's supposed to do, just shut it down, bubble wrap it and send it back so 
we can distribute it to someone who is appreciative of ever having been 
considered for one in the first place. Jees Louise !!
Jim








________________________________
From: Larry <ycsentinel at att.net>
To: meteorobs at meteorobs.org
Sent: Sunday, June 14, 2009 12:42:21 AM
Subject: (meteorobs) Improving the contrast of all-sky camera & mirror 
systems. Chris?

Picked up a commercial builders transit today with a broken tripod leg which
I intend to use to determine (true) horizon. This has started my thinking on
the faults of both all-sky camera lenses and mirror systems.

Your thoughts on the following comments Chris would be appreciated.

1) Both all-sky fisheye lenses and mirror systems capture the light from
distant terrestrial objects on an "apparent" horizon which is FAR BELOW the
actual true horizion. This includes rising and setting Sunlight saturation
at important fireball recording hours.

2) It appears that our systems see & photograph somewhere around 20 degrees
or more below the true horizon. (I have not measured that yet).

3) Our practice has been to "Mask" all of this unwanted light from
triggering our systems. But I do not believe this is the best approach
because it does nothing to help the camera sensitivity which is based on
contrast. Street lights that are close are a separate issue if they are
above the true horizon or even close to the true horizon.

4) My thoughts are that we should be BLOCKING the light below the true
horizon or maybe blocking all light more than 5 degrees or so below that
true horizon to improve the operating contrast of our cameras by reducing
the stray light, artifacts, and saturation that inhibits contrast.

5) A circular black ring, paint stripe, or similar application should be
placed around the dome or mirror with a height just below or at true
horizon. Masking should be only employed for lighted objects above the
elevation selected for blocking if no steps are taken to specifically block
those too.

This approach may significantly improve our camera sensitivities and/or the
early evening, early morning, working hours.......

YCSentinel
(P.S. thanks for your classified thoughts earlier.)

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