Well, I took some time to look this up and came out with confirmation from my mechanic (Official Skoda Repair Garage) that the grease I've been given is used for undercarriage joints, i.e. wheels joints and such. I guess it will be OK for magnifier.
From: Bob Crawley
Date: 2014 Nov 7, 05:15 -0800
Bruce Baur's book, I think, recommended Jojoba oil as a replacement for whale oil. I used some and it seems to work OK. Graphite might get a bit messy.
From: Jackson McDonald
Date: 2014 Nov 7, 13:29 -0500
I read somewhere that mariners used very light sperm whale oil to lubricate sextants in the old days. To be verified.
Just for the sake of good debate, let's not confuse oils and grease.
I have very little experience with natural oils, but after some brief homework, I came to suspect that they might go rancid after a while. However, I'll have to do some thorough digging before saying something credible on the topic. :s
As for the grease's "messy" part, the mech told me straight away that it is a "black, non-washable" thing. However, the places I intend to use it on are somewhat out of reach of ordinary user, so I guess it'll do.
From: Bill Morris
Date: 2014 Nov 7, 11:50 -0800
Ivan, For all moving parts of the nautical sextant except for the rack and worm I use waterproof marine grease. For the rack I use SAE30 spindle oil. The grease for optical eye pieces is a very sticky black grease. I don't know whether it is graphite grease, but it is also intended for use on things like exposed universal joints and sun and planet gearing, where an ordinary grease might simply be flung off. If the grease your mechanic has given you is thick and very sticky, go ahead and use it on the multi-start eyepiece threads.
As an aside,where grease is required on aeronautical sextants I use silcone grease rated for low temperatures, even though I have no intention ever of using them at altitude.
Well, since Your book won't arrive before 25.Nov (I'll have to remember not to buy anything from Amazon EVER again), which is the time I'll be stirring the seas again, I took Alex Eremenko's advice and restrained myself from any further dissasembling of the sextant (untill then, that is).
However, for the magnifier part, I made some slight mistakes already; first of all, after thorough cleaning of all movable parts, I applied a few drops of ordinary machine oil (for door locks, sewing machines and such). Needless to say - this did not work as expected; movement was very light with very abrupt endings that usually went stiff and needed some small force to turn the magnifier back again.
Then I realised my mistake, cleaned everything back again and applied some Lithium based mechanical grease - CASTROL LM.
This worked, but the resistance, I expected to encounter while turning the magnifier, was a bit too light.
And finally, I ended having a cup of coffee at my local Skoda garage, while waiting for my mech to provide a teaspoon or two of some graphite oil (mind You, when I turned up holding "kinder surprise egg" in my hand, the guy must have thought I'm a drug dealer or something; I could tell by the look on his face the Graphite grease was definitely not the thing he was thinking on). :)
I made sure that it is free of any metal ingredients because there are certain graphite greases (in widespread common use) that contain metal dust. This might have some grinding effect so it would not be suitable for fine mechanics.
As I was assured by the mech that this is exactly pure mechanical grease (probably Lithium based) with added graphite powder and no metal ingredients (hence: Graphite grease), I tried a bit between my fingers and it did feel very sticky and thick. He also told me that this is what they commonly use these days and that, if I wanted Graphite grease with metal ingredients, I have to emphasize it to him, because it is very seldom used for very specific purposes (this is just for the info to all of You who might take a stroll to Your local mech's garage). :)
Since I live in Croatia (northern, continental part) I found graphite grease to be available from gas-plumbers as well. However, I'm not sure whether they will be willing to share and in which quantities. Keeping in mind that this is the Germany-influenced part of the country, where old habits die hard, perhaps it would be best to leave this as a last resort so they would not get distracted and connect the pipes to the shower or something. ;)
Otherwise, surprisingly poor offer of small-quantity doses in local hardware stores; I found only one and I live in the capital.
Anyhow, I hope these experiences might proove usefull (perhaps to some other greenhorn like me), and I'll try applying the grease today and will post back about the results.