(meteorobs) OT -Proceeding with IR block fireball detonation system.

[Chris Peterson]

Larry-

I don't really understand what you're trying to accomplish. At the pixel 
scale of allsky video cameras, all meteors are point sources. You can't 
resolve anything- even a large explosion is still a point source. Where is 
information lost? The main problem is the low dynamic range of the camera. 
If you want to record the dimmest possible meteors, you'll saturate brighter 
ones. That represents a loss of information. A good video system with a 
maximum sensitivity of mag 2 will saturate at about mag -4, or maybe mag -6 
for a more esoteric camera. Still, nowhere near enough to accurately record 
the magnitude of a significant fireball. Of course, you can use filters to 
shift the range, but only at the expense of missing more ordinary meteors. 
(I solve this problem using a reference white target, that I can use to read 
the reflected light for bright events.)

You may also consider the effects of blooming to result in a loss of 
information. Because the shape of the meteor profile changes, it can be 
difficult to determine its centroid, and therefore the meteor position. 
Since (despite the occasional witness report to the contrary) meteors don't 
suddenly change direction, you can usually make an accurate determination of 
position by considering the entire sequence, so I haven't considered 
blooming a serious problem.

I really don't think you want to include any filters in your system. If you 
want low sensitivity for bright fireballs only, a color camera might make 
more sense, since you can extract some interesting spectral data from the 
raw image.

Chris

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


----- Original Message ----- 
From: "stange" <stange34 at sbcglobal.net>
To: <meteorobs at meteorobs.org>
Sent: Friday, November 28, 2008 10:17 PM
Subject: (meteorobs) OT -Proceeding with IR block fireball detonation 
system.


> Curiosity as to how a bright fireball might look inside the light blossum
> during an explosion is my downfall....
>
> The system being retro-fitted now will utilize an 18" hemispherical mirror 
> &
> 1/3" CCD camera with an auto-iris, fixed 8.5 mm, 1:1.3 Computar lens
> designed for a 1/2 CCD. Initial Camera a 1/3" Sony SPT-M124 will be 
> replaced
> with a PC164C. A Baader IR filter will be mounted (in) a machined adapter 
> to
> fit inside the light shield of this lens up very close to the uv coated 
> lens
> crown.
>
> Preliminary indoor tests using Handyavi set for 640X480 RGB24 (30 FPS
> unfortunately), look workable with the camera about 40" above mirror peak.
> Fingers crossed.
>
> YCS