(meteorobs) Optimized filters for daytime fireball videocapture?

[Richardson, Terry R.]

Chris and Ed,

A couple of thoughts here. I have done some work with daytime  
detection of bright stars using filters in oder to initialize GPS  
scopes. Since the sky light peaks in the blue end of the spectrum a  
deep red filter that you were sure had transmission well into the IR  
might work. The solar intensity in the near IR is still 80% of the  
visible peak, so this filtration will darken the sky but not help much  
with the sun. An infrared cutoff filter such as a wratten #87 should  
be better if the camera has sufficient IR sensitivity but I must  
acknowledge I have never tried that to detect stars in the day with a  
#87 but it sure does darken the sky making it almost black.

A student of mine had a similar problem with the full moon and all sky  
light pollution photography. We put a neutral density filter on a ring  
that covered the moon (but allowed it to shine through) and was moved  
across the sky at the same rate as the moon by an equatorial mount and  
clock drive. It would be a lot more trouble but if it works, then it  
might be worth it.

Clear skies,

Terry Richardson
Department of Physics and Astronomy
College of Charleston,
Charleston, SC

> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 25 May 2009 15:12:32 -0600
> From: "Chris Peterson" <clp at alumni.caltech.edu>
> Subject: Re: (meteorobs) Optimized filters for daytime fireballvideo
> 	capture?
> To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
> Message-ID: <4B9B6FB2D4C244F087D7E31113C289C3 at bellatrix>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> 	reply-type=original
>
> Well, I get quite a lot of flare around the Sun, as well as internal
> reflections from the dome, so I know that an occulting disc would  
> allow more
> of the sky to be seen in daytime. In addition, daytime meteor  
> detection
> requires opening the iris as far as possible- just below the point  
> where the
> sky saturates. That iris diameter would probably be large enough  
> that the
> Sun could damage the camera sensor. When I was experimenting with  
> detecting
> Venus and Iridium flares, I was careful to keep the camera in the  
> shade (not
> a problem, since I was only interested in a small part of the sky  
> for the
> tests).
>
> Chris
>
> *****************************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
>
> ----- Original Message -----
> From: "Ed Majden" <epmajden at shaw.ca>
> To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
> Sent: Monday, May 25, 2009 3:03 PM
> Subject: Re: (meteorobs) Optimized filters for daytime fireballvideo
> capture?
>
>
>> Hi Chris:
>> An interesting solution.  I'm not sure it would help with the
>> detection of daylight fireballs however.  If anyone tries this I
>> would be interested on how well it would work.  It would be nice to
>> reduce the intensity of the Sun and still record the disk with the
>> video camera.  It would make a good reference for calibration of the
>> system as the Sun moves across the sky.
>> Cheers:
>> Ed
>
>