resuced objective

After taking some advice from people on Cloudy Nights, I was able to rescue the poor objective; now I have a matched pair to work with!

At first I tried applying some water soluble lubricant around the flint where it touched the cell, but it didn't penetrate so no use there.

Next I put the cell, with sky end facing up and retaining ring removed, into a pot -- I hoped the sky end up orientation would help in case the glass just dropped out of the cell. I leaned the cell at a shallow angle using a metal spatula so bubbles wouldn't accumulate underneath it. I filled the pot with water so the cell was submerged, and set the heat to medium low for a very slow time to boil. When the water was very hot, but before a full rolling boil, I heard a soft clunking sound, as if something had shifted in the pot. And indeed the glass just dropped out of the cell! I turned off the heat and using oven gloves reached in and lifted the cell away. I let the pot sit for a few hours to slowly return the water and glass to room temperature.





There was some writing in pencil on the sides of the glass. Both glass were marked with "5-75" which I presume is the date code, May 1975. Both glass had "30.126" on them, which is the focal length. However, the orientation of the writing was different -- the crown's writing was upside down. Furthermore there was a straight line pencil mark on the sides of both glass, but the line was shifted almost 90 degrees from each other. I lifted the crown up and found, as I suspected, the more prominent convex curve was facing skyward. This and the writing confirmed the crown was installed reversed. I flipped the crown and fitted it to the flint with the straight lines lined up -- and not only did they fit perfectly, but the "30.126" numbers on both glasses were right on top of each other -- indicating this is how the Jaegers factory validated the glass.





I found some sticky residue on the edge of the glass and on the inside of the cell, so I cleaned that off. I washed the glass with some dish soap and warm water, with a distilled water rinse, and let dry. I assembled it together with the glass resting on a padded soup can, and at first had some difficulty -- I could not get them to go in. But after taking a break and giving it another try, I found the right angle and position to lift the cell into the glass, and it slid in with no problem -- perfectly flat. The retaining ring's foil spacers all make even contact on the flit.



I installed the objective back in the scope and focused with a few eyepieces on the moon. Crisp, snap to focus! Seeing and transparency were poor but a star test on Procyon showed concentric rings. What is more, I measured the focal length of this and the other objective by measuring the focus point of four different eyepieces and taking the average -- there is only a 0.01" difference between the two objectives. What are the odds of these being a matched pair?

I am so relieved to have been able to rescue this objective. Now I can work on the final ray trace and mechanical design of the binobox.