Question for the Optical Police: Am I nuts?

I own 2 refractors; a TV102 and a Stellarvue 80/f9.4 I recently realized that when viewing the moon I could almost always pick out a thin line of color on the limb with the TV102. It's not objectionable but it's there if I look for it. With the SV80 I normally don't see any color at all. In one instance I let the limb drift up against the field stop of a 20mm Sirius plossl and did see a bright band of color (green) where the limb touched the stop. Other than that the SV80 has been color free ON THE MOON. I might add that I usually use a 20mm Sirius plossl in the SV and a 20mm TV plossl in the TV102 and have not experimented using the Sirius plossl in the 102.

Now everyone knows the SV80 is an achromat and the TV102 an APO. On bright stellar objects the SV80/f9.4 will show color; sometimes a lot. I can recall trying to view Rigel in the SV80 and seeing nearly the whole FOV light up with an obnoxious bright blue and red chromatic effect regardless of the eyepiece chosen. However on stellar targets fainter than 1st magnitude it seems chromatically well behaved. The TV102 is well behaved on everything with only traces of color being seen when seen at all; but as I recall some color can always be seen on the limb of the moon.

Much is made of Vic Maris' ability as an optical tweaker/tuner at Stellarvue. Vic himself stated that he took a lot of time & effort to get the 80/f9.4 "right" before delivering a batch of them early this year. Is it possible he's using moonbeams to tune these things? Is it possible in an achromat to optimize the optical perfomance on reflected light from the moon/planets to where it's comparable/superior to an APO? Has anyone else noticed this? Is my TV102 broken? Or am I nuts?
Bob Young

Bob
Is the false colour you see off axis in the TV102?? By this I mean not in the centre of the field of view.

Another issue is how high in altitude was the moon when you were viewing it?? And another is it possible the eyepiece is introducing the false colour on or off axis??

I am sure it makes no difference whatsoever to the quality/contrast of the view.

Chromatic aberration is very subjective some folks seem to see it easily. I recall my 6 inch f-12 D&G had practically no false colour on the moon's limb, just a fleeting violet flash that seemed worse when atmosphere was turbulent. On Jupiter it was easier to see but still not a problem.

I have two Zeiss apo's and neither has any false colour seen in focus. The larger (a 130 mm) shows slightly green out of focus images with Canopus and Sirius one side and possibly purple the other side.

Bloody good really.

The limb of the moon is a tough test.

Kevin B

It could be atmospheric refraction or eyepiece aberration. One thing I noticed when I moved from an achro to an apo is that things like that are much more clearly seen in the apo.

You may also be seeing the residual color in the TV102 itself. Residual color in an apo is only _very_ slightly out of focus, so it can show up as a tiny but bright halo. Secondary color in the achromat is more diffuse, producing an overall veiling haze that may not be as obvious.

David Brodeur