I put "repair" in quotes because I don't think there there was anything wrong with it until I accidentally dumped out all the lens groups after removing the rear baffle (which was also the retaining ring!) to bet better access for cleaning. Let's hope the eBay seller is not on here to see the fate of the objective. I actually did make some attempts already to fix it. Reassembled several times randomly and one of the alignments gave a not-obviously-terrible image but still some noticeable asymmetry in the PSF.
Interesting you say that because there actually are holes like patta mentioned that access the second cell. (One original hole visible on the far left in the attached photo.) I also drilled access holes to the other cells but was rotating the cells in place was difficult. (Soft probes slip but hard ones leave divots/scratches that cause the cells to bind.) However just now I realize, probably what you are supposed to do (and why there were two opposing hole originally) is use two probes with balanced force from both sides to avoid binding. I will drill a second set of the larger access holes on the other side and try that when I get a chance.apochronaut wrote: ↑Mon Jul 05, 2021 11:33 amThat looks like it might be in the rotation of the second cell...
Yeah, I didn't disbelieve the warnings, but was surprised just how bad it was.
Didn't notice any, I will check, but not hopeful because the tolerances are not that tight and everything slides in/out freely.apochronaut wrote: ↑Mon Jul 05, 2021 11:33 amIf you are really lucky , you can sometimes find the complementary are on the barrel that caused the scratches and get a cell to barrel alignment.
No shims, luckily, just one large spacer which I'm pretty sure has to go between the 2nd and 3rd cells.apochronaut wrote: ↑Mon Jul 05, 2021 11:33 amUnfortunately, there is no easy way of getting the shim order and location correct, once shuffled.
Didn't notice any effect while setting up DF, and the image looks terrible in BF also. I did the DF on dilute milk mainly because it nicely shows the shape of the PSF.apochronaut wrote: ↑Mon Jul 05, 2021 11:33 am...try fiddling with the diaphragm/annulus relativity. Some of that image skewing might get taken up with a DF centering adjustment.
I will try again rotating the cells with two probes as I just mentioned above. There are no set screws at the front, retaining ring at the back is all that holds the whole thing together, so it seems like rotation is the only adjustment originally possible.patta wrote: ↑Mon Jul 05, 2021 12:23 pmThe coma may be fixable: remove the skirt; loosen a bit the screw that holds the lens pack. Toward the end of the objective, there are usually four little holes. With the objective mounted, observing the milk, fiddle a bit inside those holes, like with a toothpick; there is a loose lens inside that can fix collimation.
Looks interesting, thanks, and machine translation seems to be doing a reasonable job on the parts I tried so far.patta wrote: ↑Mon Jul 05, 2021 12:23 pmhttp://www.funsci.it/files/obbiettivi.pdf
(Sorry it is a pdf, and in italian. see illustration at pag. 56 for example)