90/2.8--internal reflections

[Charles Dunlap <cdunlap@rupture.ucsc.edu>]

I have a 90/2.8 that I bought new in Jan. of '97. I like the lens a great
deal, but I've had a recurring problem.

I've used it a couple of times to take long exposure photos of the full
moon lighting clouds. On both occasions the lens produced a spot in each
frame that I attribute to an internal reflection of the moon's disc. The
hood was extended, no filters were in place, and the glass was clean. I can
see no flaws in the coatings. I can see no obvious defects looking through
the glass into the barrel. The internal reflections appeared first on color
print film and then on Kodachrome--they aren't coming from some trick of
processing. I haven't noticed my Canadian 35 Summicron doing this.

Is this a limitation of the lens? I'm hoping that someone with experience
shooting similar scenes (dark background, strong light source) will let me
know if he (she) has similar problems with the 90/2.8.

I can send it in under Passport Warranty, but I don't want to if the
problem really can't be fixed.

- -Charlie