[Aavso-photometry] Light box question

[arne]

Robert J. Modic wrote:
> I've been using a light box to take my flats with for a few years 
> now and am generally satisfied with this method.  Twilight flats 
> are problematic from my site due to weather and time constraints, so 
> the light box gives me more flexibility.  However, there are sometimes
> residual artifacts in my images made with light box flats, especially
> in stacked images.  These are usually at the ~1% level and affect 
> mainly the edges of the frame.  I'd like to improve on this.  
> 
> Since my L.B. uses tungsten light bulbs which emit a lot of IR, there 
> is a mismatch between that and my night sky which has a fair amount of 
> light pollution and, on some nights, moonlight or twilight.
> 
> I'm looking for some material that I can place over the front of the
> L.B. to make its output more neutral (white).  Perhaps a light blue
> plastic sheet might accomplish this.  Does anyone have any suggestions
> for specific materials that I could use for this purpose?
> 
It is better to place something around the light source than in
front of the light box; usually all filter-type material is shiney.
If you are using a standard 110V lamp, the Reveal bulbs have a
built-in blue tint that might work.  There are a number of halogen
bulbs that are significantly hotter/bluer than straight tungsten.
You could paint the tungsten bulbs with blue paint.  If you have a
lot of light pollution, you could consider "T-shirt" flats and
just get night sky flats.  My choice would be the latter.
Arne