So, will I get the optics clean (Wild drawing tube)?

[jfiresto]

I have two surfaces like this in each infinity optical path of an old, Wild M3 drawing tube:



The dust is killing the image brightness and contrast but is not doing much to the resolution from what I can tell so far. It appears I will be the first to open the tube since it left the factory more than forty years ago. This makes me a little nervous: any scratches that appear will most likely be mine.

[Charles]

Have you tried blowing it out first and then use a long handled soft brush?

[BramHuntingNematodes]

You'll be fine if nothing else you will learn something

[Scarodactyl]

My experience with Wild stuff is that they're made to be possible to service. That said, they sometimes applied light threadlocker to screws as well, which can be a pain to get through. Probably not on this one though.
A hurricane/squeeze blower would be a good idea here.

[jfiresto]

Thank you all for the suggestions and encouragement. A large Giottos Rocket Blaster took off a few specs: the above image shows what would not budge. I can not find any cleaning scratches, so some of the dust may been stuck there for decades. I would say I have a few days to ponder my next move. Meanwhile, I think I will store the drawing tube under formaldehyde gas as there is probably plenty of fodder to germinate a chance fungal spore.

[apochronaut]

For large surfaces like that and a fair amount of dust, I make a small equivalent of a feather duster out of 3 or more cotton swabs bound together side by side. I then tease the fibres so that a continuous wide and soft " brush" results. Moistening that with isoptopyl and one or two wipes across the surface and most dust is collected. All that is left is to finish cleaning with swabs, other lens cleaner or isopropyl alcohol, if there is no oily residue, something not uncommon on older lens surfaces.

[PrecisionInstruments]

If you place a picture up of the entire drawing tube from both above and below, I will annotate the image with arrows explains how it’s comes apart. They are quite simple.

It may take me a day or two to check back in though.