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Re-lubricate Jupiter 8

Open back · Remove meter scale · Focus worm gear and lens block · Aperture scale and front lens · Re-greasing and reassembly

The Jupiter 8 lens is a replica of the legendary Zeiss Sonnar. It has a maximum aperture of 2.0 and a focal length of 50mm.

This model belongs to the second series from the 1950s. It still has the focus knob, but instead of two focus worms like the previous model, it now has only one. This makes disassembly much easier.

1. Open back
	This lens is really not a thing of beauty. It was almost impossible to focus and the chrome looks very dull, so we'll take it apart, clean it, and re-lubricate it. The lenses, on the other hand, are very nice, with no scratches or glass fungus. First, we remove the 3 screws on the back and take off the 2 rings (left and bottom).

	Remove the black locking screw that prevents the lens from being turned out of its mount (left).
2. Remove meter scale
Then remove the 3 tiny grub screws that hold the meter scale in place.	Note the tiny grub screws! They can easily get lost.

3. Focus worm gear and lens block
	After removing the locking screw, the focusing worm gear can be unscrewed. Be sure to note the position at which it comes out of the thread, as this is where it must be screwed back in (left). The lens block should now be unscrewed (counterclockwise). If it is very tight, rubber gloves can be used to assist. Be careful of the metal shims, which may fall out! They must be put back in during reassembly (bottom). The rear lens block can be unscrewed quite easily.

4. Aperture scale and front lens
The aperture scale can be unscrewed after removing 3 grub screws. Mark the position at which it will be screwed back on and note the number of turns.	Two more grub screws hold the front ring, which can then be unscrewed to remove the front lens. Unfortunately, one of the grub screws was broken, so I couldn't remove the front ring (bottom).

5. Re-greasing and reassembly
	After removing the old grease (using cleaning solvent and a toothbrush), re-grease the focusing worm gear. I use lithium-based grease, which you can get from bike shops, for example. Then put the worm gear back in the spot you marked earlier, put the locking screw back in, and put the focus ring back on. After cleaning the lenses, screw the lens block back in. Don't forget the shims! (left and bottom) I was able to restore the gray and rough front ring to a reasonable condition with some sandpaper and steel wool. To polish the chrome, I recommend using polishing cotton wool, which can be obtained from motorcycle accessory stores, e.g., NevrDull (bottom).