Working distance 185 vs 195

[SWmicro]

The distance between my 60x achromat objective and coverslip is amazingly small, resulting in the occasional crash ! The 40x is also a bit close
No worries, I bought cheap ones via ebay especially to practice microscopy with They are 185 conjugate, would it be better to buy the slightly more expensive 195s > would the working distance be much different (better)?

(PS the short parfocal of about 35mm vs the 45mm spec is no problem I have plenty focus travel)

[PeteM]

The "185" objectives have a shorter parfocal distance - typically used in older or cheaper microscopes. The "190" objectives have a 45mm standard parfocal distance from where they seat in the turret to where the focus on a specimen would be.

Generally you want them all the same parfocal distance to avoid crashing objectives into the slide.

Neither type automatically gives you more distance between the end of the objective and the slide. Generally, the higher the magnfiication, the shorter the distance. While there are some long working distances, some high power ones won't even see under a thick coverslip.

One trick to avoid crashing into the slide is to look from the side as you bring a high power objective very close to the slide. Then always back up the focus.

[SWmicro]

Thanks.
They (4, 20, 40, 60) are all the same on the turret, parfocal short barrel, 35mm, 185 type, not a problem.

The 'looking from the side trick' is unreliable with my eyesight, too small to see clearly and reliably especially with the glare from the light that I have (I should do something about that !) and requires a change of spectacles which does not help.
So I have always been backing off the focus when moving from the 4 and 20 on up to the 40 or 60, and lowering down to gently bring back to focus !

Just that sometimes the best laid plans go astray ! Especially when chasing rain-water / pond-water critters,

and so I got to wondering if the 195 conjugate [45mm parfocal, but that wouldnt be an issue cos I would not mix them, I'd buy the full set] also cheap type, achromats would have more clearance for 'mistakes'.
Bottom line,
If that is not a general rule with the cheap ebay types then I'll carry on being careful-ish !

Edit : added later : PS. I usually use No.1 coverslips. I have No.0 as well but keep them for special occasions