Any way to avoid rainbowing through a condenser lens?

Pardon if this ends up being a repeat - Google hiccuped when I
submitted the first time, I waited several minutes and it still hasn't
appeared so I'll try again.


Projecting 8mm film through a 6.5" uncoated plano convex condenser
lens, there's this light "rainbowing" that appears on the left side of
the image, with the convex side facing to the right. A short example
posted here:

http://home.mpinet.net/~docsavage20/rainbowing/rainbowing.html

The file is about 5 megs.

Admittedly it's subtle and only noticeable under circumstances such as
shown - against a grayish background like in this example. However I
can see it and wonder if there's any way to get rid of it? Why does
this happen? And why from left to right like this? I also get a similar
effect going through a smaller - 2.5" - achromatic lens.

Thanks for all input.

 

Doc, I looked at the clip multiple times and could not see anything where
you drew the arrows. What I did see is that the nominally gray background
appeared to change color balance during the clip. It appears reddish to me
at the beginning and bluish at the end.

 

I tried different codecs to find one that had the most clarity within
the size limitations I'm working with. I'm on dialup and have a 10 meg
limit on my ISP's freebie website. Of course, it is subtle, and the
monitor I'm using may be brighter than the one you're on - one of the
reasons I like it, it's got great color.

The tips of the arrovs follow the curvature of the outside of the
rainbow. It's most readily visible in the portion when panning between
the two fountain towers.

 

I looked again, still cannot see it. I also suspect that my monitor is not
as good as yours.