What have I bought?


I am new to microscopes. By chance I have recently bought a used Lomo biolam microscope. It has four (achromatic) objectives: 8x, 20x, 40x Wi and 90x Oi.
So now I am looking for one objective with lower mag. than 8x and one in between 40x and 90x.

I found this used objective: lomo AC f-2.8x1.25… I did I little research and concluded that “f” stands for focal length in mm and the other number is N.A. Then i calculated the mag. by dividing the optical tube length ( in my case 160mm) with the “f” of the objective in question and got just shy of 58x… and together with the generous n.a. of 1.25… I thought this is just what I want… so I ordered it.

But then i have done some further research and now I am having doubts… Because I have read that dry objectives can not have n.a. greater than cca.: 1.0… and this one has a whooping 1.25 ( as much as the 90x Oi). So that cant be right. Right?

What am I missing here? I can not find much info on this particular objective. So please, tell me what have I bought here?

Will this be usable for me at all? Is this oil or water immersion objective… given its large n.a.? Any info is much appreciated.

Also. Since the microscope itself was not very expensive, I (erroneously) thought additional objectives and eyepieces will be the same. Now I am looking in to buying new ones from china, since they are readily available and cheaper than original lomo stuff.

I only have one k7x eyepiece. Will eyepieces and objectives from aliexpress (for example) work with this microscope? I would like to buy a 5x, 10x and 15x eyepieces and a 5x and 60x achro. objectives… Would this be a sensible upgrade? Are this modern import optics better or worse than original lomo optics? Should i just spend more on the original accessories? While I do like the idea of keeping it original, I would rather go with the cheaper option unless this compromises overall optical performance… Please share your thoughts on this…

I think 195mm objectives should work with this microscope since it has a lot of travel - right?.. or should I go for the 185mm ?

Are these import eyepieces also corrected (three lens design)? I can not find what kind of design they are.

Also… how come I can not seem to find any zoom eyepieces for microscopes?
I have I zoom eyepiece for my telescope and find it very usefull… could it be adapted for microscopy use as well? Has anyone done this? please share your thoughts and experiences.

Thank you for your help.

Best regards, Bor