(meteorobs) OT -Test on CCD IR & Fireball bloom.

[Alister]

Thought from the sticks.... not sure if it plays a role here...

All cameras cannot focus both white light and infra-red at the same time 
(unless the depth of field is incredible). Typically I have seen that stars 
that are red are large on the CCD not because they are bright (which they 
are), but more because they are out of focus. And when something is 
considerably out of focus, other effects like vignetting may come into play. 
Remember what an out of focus star looks like through a scope?

I apologize if this is not helpful.
Alister.
----- Original Message ----- 
From: "stange" <stange34 at sbcglobal.net>
To: <meteorobs at meteorobs.org>
Sent: Wednesday, November 26, 2008 3:37 AM
Subject: (meteorobs) OT -Test on CCD IR & Fireball bloom.


>
> Since the daylight camera is down for retro-fit, I ran some repeat testing
> on it in regards to the excessive meteor & fireball bloom from near to the
> far INFRA-RED. The results are a disaster, but there is an easy solution 
> for
> non-AllSky camera's.
>
> The purpose of this test is to see to what extent CCD cameras +& their
> pictures distort the appearance of a fireball as compared to what the eye
> would see during the same event.
>
> This test also included a black IR dome transparency test as normally 
> found
> in casino's or in surveilance use. To sum this particular test quickly,
> those IR domes are just super dark sunglasses with little transparency in
> visible light. It takes a low light camera to have any chance on seeing
> through them at all. But as far as infra-red goes, they are completely
> transparent, like nothing was there at all! --Rather useless for meteor 
> work
> except in special applications. Now back to the main IR test....
>
> This main test was conducted on a typical  1/3 CCD HAD camera with two
> lenses. One lens is an auto iris, the other is a fixed iris. Both were 
> about
> 8mm focal length. One purpose of this test was to determine if excessive 
> IR
> bloom would cause an iris to automatically reduce aperature during a bloom
> thus diminishing background detail or fireball detail. A reference LED 
> light
> was used which had little IR transmission as a control. Throughout the
> testing the reference light diameter & intensity did not change which 
> means
> no background detail will be diminished from most bright fireballs.
>
> A Baader IR blocking camera filter is used in this test for image 
> comparison
> of a hot object to that same object without an IR blocking filter. Our
> individual eyes can expect to see a fireball or hot object the same as 
> would
> be seen by a camera with an IR blocking filter.
>
> This link to my website contains several graphs and a summing photo of the
> test.
>   http://www.geocities.com/stange34@sbcglobal.net/CCD_IR
>
> Graph (A) depicts the eye response to color wavelengths in nanometers.
> Graph (B) depicts where the visual colors are in a broad spectrum UV thru
> IR.
> Graph (C) depicts the typical bandpass response of a CCD camera compared 
> to
> colors.
>  (Notice how far into the infra-red the CCD camera can see. Far beyond 
> what
> we see.)
> Graph (D) is the IR blocking filters response. Nearly perfect in the 
> visible
> spectrum with excellent blocking of most IR.
> Photo (E) is pictures taken in a totally dark enviornment with a burning
> cigarette as the IR source with and without an IR filter in front of the
> camara lens and using both lenses. Focus was not perfect on the fixed iris
> lens, but that is not the issue. Detail WITHIN this infra-red source
> IS. --Notice dark ash is clearly outlined within the heated areas with a
> filter.
>
> Are we missing something important in our fireball pictures taken with a
> CCD?....
>
> YCSentinel
>
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