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Natural Science Forum / Physics / Optics / August 2007B&L Stereozoom 7 Objectives
Since Ed mentioned his Stereozooms, I would like to know if anyone has a source for an objective lens pair (it seems to be a single piece) for a Stereozoom 7. The one I got looked dirty; I tried cleaning it, but no good. I then removed the lens to clean the rear of the glass, but it turns out that the front surface has a matte finish! I don't know what could have done it, since there are no obvious deep scratches. I still am able to use the scope, but there is a haze to the image, and the detail, of course, is crap (so now I'm using my old B&L Stereozoom 3). I really like this instrument, and would like to be able to use it again. A lens off of a "parts" machine would be fine, or a NOS lens would do, as well. BTW, I wondered if the lens clouding could be due to a fuming acid, or other noxious stuff, but there seems to be no damage to the rest of the underside of the scope - just the glass. Thanks, Joe > Since Ed mentioned his Stereozooms, I would like to know if anyone has a > source for an objective lens pair (it seems to be a single piece) for a [quoted text clipped - 12 lines] > > Thanks, Joe: On your BTW, I guess it depends on the acid. Certain corrosives prefer attacking glass and not metal, especially if the latter is coated. But it's academic as part of your concern. I've seen odd damage when some folk brashly decided to do microabrasive cleaning while working through the scope but here that would pretty much mean that they decided to protect the rest of the scope body while jeopardizing the valuable element...which seems deliberately dumbfounding. If there is a discernible pattern to the clouding visible under magnification that would be forensic. Ebay has some section where you can post an item wanted ad. Please follow up with a report if that works. As well, asking the group to suggest sites where other enthusiasts gather might give you further venues for useful inquiry. When I identify the parts needed for my restoration project, I can include mention of your want in the distributed bill of particulars and relay the information to you if there is a bite. At times, I see miscellaneous aggregations of parts but then it would be a matter of you still wanting the item and me finding it in time. This will happen at industrial auctions. What use one would have for the other collecteana you'd get in such a mixed lot is a sane question to ask.You can find it. It just depends on whether you want to pay what is asked now or await the opportunity if and when it arises. Regards, Edward Hennessey Hi, I wonder. If the cloudiness is from soldering there are two possibilities. The solder might have been one used for delicate electronics. This kind uses a flux which is a noncorrosive resin and might wash off with an organic solvent. Then there is a rather corrosive flux material which uses some acid and this might have damaged the lens permanently. It may be worth your while to check this out. GR. but leaves deposits, which can be washed off with solvent. > > Since Ed mentioned his Stereozooms, I would like to know if anyone has a > > source for an objective lens pair (it seems to be a single piece) for a [quoted text clipped - 40 lines] > > Edward Hennessey > Since Ed mentioned his Stereozooms, I would like to know if anyone has a > source for an objective lens pair (it seems to be a single piece) for a [quoted text clipped - 14 lines] > Thanks, > Joe I've seen this before, usually it happens from soldering. Apparently the solder smoke micro-pits the coatings making the lens unusable. I've usually told the customer, usually industrial to either replace the lens or just throw the microscope away, the lens replacement is just to expensive. Now a better way to approach this problem is to buy a plain glass holder which screws into the lens assembly. These are very easy to get for major makers and quite cheap. In an industrial plant its better if the customer invests in these and some replacement glass, its a lot cheaper to buy a plain piece of glass and not have to buy a microscope. Thanks, Kevin Cunningham SMS Thanks to all who have replied so far (and to those who will reply in the near future). GR - I had already tried various organic solvents with no luck. Solder fumes may be the culprit, though. Kevin, you commented "...just throw the microscope away, the lens replacement is just to expensive." With Capovani selling used Stereozoom 7 pods for $1200, it seems as though simply replacing the lens shouldn't be too bad. How much will one of these lenses cost (assuming they still are available)? Who could I contact to find out? Ed - I would be satisfied waiting for a decent box of parts to come up. I've had this scope for several years already, and I've got more time (and patience) than money. A pod with a bad zoom mechanism would be an ideal thing. If you come up with such a deal, you can contact me at jgandalf at mindspring dot com Thanks, Joe > Thanks to all who have replied so far (and to those who will reply in > the near future). Well, now I've encountered something quite similar today with spoiled lenses. I received a couple of old enlarger lenses today. On inspection, the front surface had a kind of smeared look, like a film of clear grease, but hard and resistant to cleaning. I did the usual cleaning, which didn't seem to take it off, and finally disassembled the lens to get the glass element out. After some increasingly aggressive cleaners (starting with butyl cleaner, then naptha, xylene, CLR, and finally potassium hydroxide) I managed to clean the smear off, revealing an etched area where the smear had been. I suspect this is a type of fungal adherent and damage. It was in an annular pattern that mostly spared the center of the lens, as if it grew on contaminants that were at the edge of the lens that's hard to clean. This is not the usual spidery-filamentary growth you see inside a lens, but a kind of surface sheet that appears like a creeping mycelium (http://en.wikipedia.org/wiki/Mycelium). I'm still trying to figure out this lens fungus business. This guy seems to have some respectable scientific analysis, versus the superstition that a lot of photographers harbor: http://www.mypentax.com/Fungus.html No doubt lens fungus is a real problem, but it still baffles me that lenses have this peculiar vulnerability to it, to the point of utter ruin. In advanced cases, the fungus isn't just there to be cleaned off, but has etched and ruined the optical surface. > > Thanks to all who have replied so far (and to those who will reply in > > the near future). [quoted text clipped - 28 lines] > ruin. In advanced cases, the fungus isn't just there to be cleaned off, > but has etched and ruined the optical surface. I've seen this kind of damage a lot here in the southeast. Its common to see older camera lenses from the coastal regions with damage from bacteria or molds. They grow on the coating material, appearantly, and the damage is impossible to get rid of. I haven't seen this on microscope lenses, there is a huge difference in the use of microscopes and cameras. Thanks Kevin Cunningham SMS > They grow on the coating material, appearantly, > and the damage is impossible to get rid of. "Grows on the coating" is indeed part of the lore, but I can't believe a living thing could find nutrition from submicron-thick MgF2 and the like. I suspect that surface films and contaminants like oil and dust are the attraction. You can have fungus growing without necessarily damaging the glass. The damage is said to stem from enzymes and acids secreted by the fungus as part of its digestive process, which occurs outside the organism. Kind of like an inside-out stomach. |
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