Condenser Alignment Problem

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J_WISC
Posts: 107
Joined: Sun Mar 06, 2022 7:28 pm
Location: Wisconsin, USA

Condenser Alignment Problem

#1 Post by J_WISC » Mon Jan 30, 2023 6:19 am

Hello.

Regarding a simple 1940s AO Spencer binocular compound microscope …

I aligned the condenser with the right eyepiece. It is no longer aligned with the left eyepiece, but appears shifted slightly up/down in the field of view. And vice versa.

What should I investigate next? Is this likely an internal optics issue beyond easy fix? What’s the effect on image quality if beyond fixing?

Thank you for sharing your experience.

PeteM
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Location: N. California

Re: Condenser Alignment Problem

#2 Post by PeteM » Mon Jan 30, 2023 7:26 am

Your scope's head is likely out of alignment. This sounds like an older finite model - might want to post a photo of it. Slight misalignment can sometimes be adjusted by moving eye tubes. Somewhat larger misalignment may require adjusting prisms (one of which may have been knocked off its factory position). If the diopters are set radically different or the eyepieces not matched, that can also affect the appearance of where something like a condenser or field iris will show up.

In any case, the head rather than the condenser is the likely culprit. Some folks can tolerate slight misalignment. Strains the eyes and patience of most others.

apochronaut
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Re: Condenser Alignment Problem

#3 Post by apochronaut » Tue Jan 31, 2023 7:59 am

There were two models of binocular head that Spencer used in the 1940s. One is a prewar design that goes way back to the infancy of their binoculars and the other postwar. There are differences in the mechanism that was used to spread the eyetubes during interpupillary adjustment. With the older design, as the original grease dries and becomes stiff, one side of the brass double claw that transfers the movement of one eyetube to the other can break so only one eyetube moves. It might not be readily noticeable if the interpupillary adjustment isn't moved but shows up as a slight assymetry of the eyetubes, made a bit more difficult too by the parallax angle the eyetubes attain. If the case, that might cause the effect you are noticeing without the head being out of alignment.
If your interpupillary adjustment is located as a gnurled ring around one of the eyetubes, check to make sure that when adjusted, both eyetubes spread apart not just one.
The postwar design uses a central wheel positioned for thumb control with a grooved double gyre and double pin drive. I have not seen that one fail but anything is possible with mechanisms.

J_WISC
Posts: 107
Joined: Sun Mar 06, 2022 7:28 pm
Location: Wisconsin, USA

Re: Condenser Alignment Problem

#4 Post by J_WISC » Tue Jan 31, 2023 2:44 pm

Hello PeteM. There IS other evidence someone might have damaged the binocular head. The right eyepiece is a very tight fit. I wonder if it is slightly bent forward/backward. Thank you for your help. I will look into this before messing with prisms.

J_WISC
Posts: 107
Joined: Sun Mar 06, 2022 7:28 pm
Location: Wisconsin, USA

Re: Condenser Alignment Problem

#5 Post by J_WISC » Tue Jan 31, 2023 2:54 pm

Hello apochronaut. The interpupillary distance is adjusted by a ring on the right lens. It is difficult to move, probably due to age of the grease. Is it okay to put a tiny amount of sewing machine oil on it to loosen it? I used sewing machine oil to loosen the mechanical stage, but worried the oil could get into the head and drip on the prisms.

Sorry, no photos. I’ve not figured out how to directly reduce iPhone photos for the forum. I must find time to send them to my desktop computer, then post. 😑

apochronaut
Posts: 6233
Joined: Fri May 15, 2015 12:15 am

Re: Condenser Alignment Problem

#6 Post by apochronaut » Tue Jan 31, 2023 9:07 pm

This might seem excessively complicated but it really isn't. I can send some pictures tomorrow if these instructions are a fail.

The grease on those can get hard. Earlier ones are often in better condition because they still used whale wax as a grease base. During W.W.II the high military demand for unique lubricants limited whale oil use for consumer goods and petrochemical lubricants moved in, never to be supplanted. The early petroleum greases have not stood the test of time.
Something like 3 in 1 oil can usually help out, when introduced to the right locations but the removal of just 5 screws and two components will give you access to all of the spots that become tight on that head due to lubricant desolvation.
1) the rotating collar itself comes off with 1 track screw embedded in the knurled ring itself. You might as well remove it because it then allows easier access to other lubricating points.There is one nickel plated about 2mm slot head screw in the knurled ring which serves both as a guide screw and a locking screw. Just loosen it a couple of turns until you can lift the control ring off of it's sleeve bearing . This also removes it's attached pin drive to the right side.
2) You can then remove the 4 2mm slot cheese head screws that fasten the L shaped centrally mounted left hand claw drive mechanism. That's it. You can now access all of the lubricating points. Hopefully the relatively fragile claw teeth are intact.
3)The 4 dovetail slide rails( 2 on each side) can be almost entirely accessed by manually sliding each to it's minimum below 50mm and ,maximum above 70mm extremes.

At this point you have to make the decision to remove the existing lubricant and regrease with damping grease or just solvate or emulsify the existing wax. I have done both but the latter on those heads in fact works as well and saves a lot of time. Removing the adjustor side of the female dovetail slides and lifting out the prisms is time consuming and if the prisms are in fact in need of adjustment, you can't do it that way. It does make cleaning the prisms easier.
You also at this point need to check and see if the dovetail slides are tight. Take each eyetube in turn and manually try to wiggle each back and forth( not side to side). If they are snug, great. If not, that could contribute to your problem. If loose at all, adjust them after lubricating them.
To lubricate. You will be lubricating 10 points with a 1mm drop of oil at each point initially, maybe one more if needed. Always position the head so the drop will run into a mechanism with gravity if possible. None of these lubrication points are anywhere near to optics, so with judicious lubrication there should be no chance of contamination.
Open the interpupillary distance fully. Turn the head on it's left side and put one drop of oil on the inside of the two brass bevelled surfaces exposed on the right side of the right dovetail and the two exposed flat aluminum sliderail surfaces closest to the right side of the left eyetube slide plate. Closing and opening the interpupillary distance manually a few times will work the lubricant into the slides. Repeat by turning the head over on it's right side and oiling the other 4 similar but opposite surfaces and then work the slides. Once the action is smooth, you can then tighten the dovetails if needed. Each has 3 cheese head slot screws at the back side to tighten the back external or female dovetail slide. Close the interpupillary distance for both sides fully. Unscrew the 3 screws on one side about 3 turns but do not remove. Then , gripping the front and back female dovetail slides between the thumb and index finger squeeze the back rail snug, while tightening the middle screw just lightly snug, then the outtside screw and then inside. Then tighten those two firmly, followed by the middle screw. Repeat for the other side. Open and close the slides several times to test for tightness and uniformity and adjust as needed.
Next, smear a couple of drops of oil on the sleeve bearing, install it and rotate it around and around until it feels silky smooth. Add a little more oil if necessary. Remove it again and set aside. Put one or two drops of oil under the central pivot of the claw seesaw and a tiny bit of GREASE in each claw proper. Rotate the seesaw to a vertical position. Close the interpupillary slides until the drive pins are in a vertical orientation. The claw bracket should just slip between the eyetubes and right onto the pins. Line up the screwholes and install two screws diagonally. Check to see if the claw is engaged on both pins by pushing and pulling on the right side tube. The left side tube should also move in both directions with it and easily and smoothly. If not you will have to retrace steps to find out where the resistance is . Install the other two screws and then place the control ring over the right eyetube, engaging the drive pin in it's groove and tighten the track screw.
Everything should be snug and smooth.

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