Vixen Fluorite - Newton's Rings

I have just acquired a cosmetically excellent condition Celestron branded Vixen Fluorite. And I noticed what appears to be Newton Rings in the Objective. See the photo below.

I have owned several of these telescopes over the years but do not recall seeing such a strong Newton Ring pattern. This pattern is visible even in low light conditions. Can anyone tell me what causes this; and is it detrimental to the view? This is an airspaced doublet with the Fluorite element uncoated and on the inside.

Attached Image:

It means that the elements almost touch each other only in the center. What would be the effect on the picture I guess only the lens designer would be able to tell (i.e. what was the designed spacing etc.)
If you are concerned, the best way would be to take a Roddier test.

Hi Paul,

The brighter Newton's rings does not affect
anything you need to worry about. My best guess is that
the coating on the R2 surface must have changed between
these early C102F and the later models where the rings
are difficult to see.

The rings are from constructive and destructive interference
of reflections from the R2 and R3 surfaces. If "A" and "B"
are the reflectivities of the two surfaces, the rings
will range in brightness from A+B to A-B. We know
R3 is uncoated Fluorite, so B=3%. If R2 is completely
un-coated A=4%, and the rings will run from
7% to 1% brightness. Or if it is a single-layer 1/4 wave
MgFl coating on R2, you have A=1% and the rings
run from 4% to 2% brightness. I suspect the modern
versions have multi-coating on R2 so A=0.2% and the
rings run in brightness from 3.2% to 2.8%, so are very
hard to see -- the contrast in the rings is very low.
My feeling from looking at the image you posted,
is that probably R2 is uncoated in the older scope,
or has a thin single layer MgFl coating.

There are also scenarios where the a difference in
the air space thickness could contribute to the differences
in appearance. I cannot rule that out, either.
The modern version would have a thicker air space,
in that case.

I did have a close look at a modern Vixen 102 FL, and
the ring pattern is definitely there, and has roughly
the same position and size. It is just extremely weak
and hard to see.

I don't think any of this affects anything you need to
worry about.

- John B.

Paul,

I just checked my C102F using different lamps in the room where I store the telescope and I cannot detect any Newton's Rings. I'll try again during the daylight tomorrow, If I see any I'll post a second post.

Jim