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Inexpert Binocular Cleaning
Summary: io1o discusses common issues with binoculars found on eBay, often caused by inexpert disassembly. They explain that improper reassembly, such as cross-threading the objective lens barrels or swapping them, can disrupt collimation and focus. They advise careful handling and proper alignment markings when taking binoculars apart to avoid these issues.
I frequently see binoculars offered on eBay that have been put out of collimation by inexpert disassembly. I even buy them, as it is an easy thing to put right. It happens when someone unscrews the objective lens barrels to clean the inside, and cross-threads one or both when reassembling. Sometime you can even see it in the photos, as a gap between one side of the barrel and the housing. A lesser problem is caused by swapping the barrels left to right, which affects the collimation even when screwed in properly, and can alter the balance between the focus on both sides, causing the diopter adjustment to lose much of its range. I have just repaired a pair of 12x50s that had one cross-threaded barrel, possibly in the wrong side, and the objective lenses also swapped onto the wrong barrels. Something of a puzzle to sort.
Binoculars leave the manufacturer with critical adjustments made to align collimation and focus, and these simple mistakes when people reassemble them improperly render them almost useless. Don't do it. If you must take them apart to clean out dust etc, make sure you mark them for reassembly in the right sides, and take care not to cross-thread them. The threads on the housing are only about two-thirds of the circumference, so it is easy to get it started wrong. If it isn't easy to screw in smoothly, you are probably cross-threading.
tressygirl
Mentor2 weeks agoLets hope all binocular sellers see your expert, and very detailed post on binocular cleaning!
@io1o