Servicing Oil-spaced Objective

Hi All,
I have a challenge that would benefit from your experience and knowledge. I've come into a home-built "Steampunk" refractor from the 1940's, with a home-fabricated 82mm clear aperature f/17 objective. This lens is about 63 years old! The views are exquisite, with very clean detail on planets and nicely split doubles, and text-book excellent airy discs that will make grown men cry. My only complaint is the large haze that surrounds bright objects. It really isn't a "ghost" in the sense of displaying a small replica of the object being viewed- this is a large haze. The moon doesn't show a sharp limb, but rather a haze that extends quite a bit beyond the limb. This kills contrast, obviously.

The lens is oil-spaced (no spacers), and has a strange (to me) seal of unknown substance around the circumfrence.

My questions: Is the haze a result of the oil "going bad" and needing to be replaced? Is it possible for a reasonably capable ATMer to do this, or would this require professional service? What resources would you recommend for me to learn how to re-oil the lens? What professional services might you recommend?


Any thoughts or advice you might have on this subject would be greatly welcomed. Thanks in advance!

-Steve

Steve-
I am no expert on this, but I do own an oil spaced objective, a TEC 140 and here is what I believe to be true...

Only two companies in the US currently produce oil spaced telescope objectives...TEC and Astro-Physics. So I would suggest that perhaps one of those companies may do the service, if the fee was right and they had the time.

In terms of the "oil," I know that TEC uses what they term an "immersion liquid" that they distinguish from "oil". So if you were even considering doing this yourself, you may want to try and find out exactly what it is that TEC or Astro-Physics uses...and I would hazard a guess that this knowledge may be proprietary.

I know that is not much help, but maybe you can contact TEC or AP and go from there.

Alan

I'm not an expert on oiling lenses. It's probably
difficult to know what it was oiled with, and hence
hard to predict long-term issues like haze. I'd suggest
to make some tests.

(1) Try to rule-out some sort of turn-edge or
oil problem right a the edge. Make some cardboard
or black paper masks with say 75mm, 70mm, 60mm holes
and see if masking off the outer bit of the lens makes
some large improvement on bright objects. Maybe it
won't, but easy enough to try it. If something like
a 75mm masked fixed it, I might be tempted to
make a more permanant mask and otherwise leave it alone.

(2) Try shining a laser pointer through the
lens and see where the light goes. Does the laser
beam gain some halo when shined through the lens
that not there alone, or with similar lenses.
Does the beam show a lot of light scattering
at either of the surfaces or the oil space.
I'm wondering here if the front surface
might be pitted or hazy.

(3) Get the lens + cell off the scope and hold
it up to a bright light. Does anything look hazy?
Is the haze in the oil space? Front surface?

I expect a reasonably capable ATMer could attempt to
re-oil the lens. Assuming the elements separate easily, you could
clean them well with 91% rubbing alcohol. Get some
high viscosity immersion oil from your favorite microscope
supply outfit. I might consider adding three spacers
around the edge (thin adhesive tape) to make future
disassembly easier. Put a couple drops of oil
on the concave side and slowly/gently lower the
convex side. Obviously you need to avoid bubbles.
Wipe excess from the edge and seal the edge it with something like
electrical tape (being mindful that it needs to fit
back in the cell).

Where I think you could get into trouble, is if the elements
don't want to separate. Then some experience as to using
solvents or mechanical means would be very valuable.

Alan mentioned two outfits that might work on it.
Some other people who probably have the skills are
Wolfgang Rohr (Germany)
http://rohr.aiax.de/hp_new/
and Roger Ceragioli (Arizona) who has made some oil-spaced lenses.

Also Markus Ludes (Germany) can probably refer you to people
with experience re-oiling old Zeiss lenses.

There is some discussion of oiled lenses at
http://bobmay.astronomy.net/refractor/Refrdesign.htm

Good luck!

>>My questions: Is the haze a result of the oil "going bad" and needing to be replaced?>>

I doubt that the oil is to blame. Hold the lens up to a bright fluorescent light in a darkened room. You will probably see haze on the front or rear surfaces. This is weathering and is impossible to remove by any cleaning method. You will most likely need to repolish these surfaces to get back the original clarity of the glass.

Rolando