objective hits the slide

[Judge]

I cannot use the larger objective because it will hit the slide. What are my options?

[dtsh]

A lot (most?) of microscopes have an adjustable stop to limit the chances of crushing an objective and slide together. What brand/model are you using?

Edit: I am aware of some people who will lower the objective while watching it and bringing it down to the slide, then adjusting focus by raising it as a way of avoiding that.
I've become so accustomed to the AO infinity systems that I forget it's a concern for many

[PeteM]

It might help to post a picture of your microscope and objectives, Judge. Could be several reasons why and several solutions.

[DonSchaeffer]

When does it hit? Is it when you try to focus? Maybe your subject is too thick. You may even have the slide upside down (cover glass on the bottom). I have done that.

[Judge]

https://m.media-amazon.com/images/I/61f ... L1500_.jpg
What about using 2 covers instead of a slide?

[Alexander]

I still don't understand why you cannot use the longer objectives. Is there not enough room under the objective even with the stage fully down? Or do you have problems to find focus with the longer objectives and run into the cover glass on the attempt to focus?

[PeteM]

The posted catalog image appears to be a model which uses "short barrel" finite objectives. It's possible that the 100x objective you have wants to have 45mm from the nosepiece to the cover slip and that the others want to be nearly 10mm closer. If so, you want to get another 100x objective of the same type as the others.

[Judge]

Can't focus with the longer objectives it runs into the cover glass on the attempt to focus.
I'll look into other objectives.
Thanks guys

[Judge]

I do have an adjustable stop. Can I do damage by messing with it?

[PeteM]

I do have an adjustable stop. Can I do damage by messing with it?

You may be able to set it so your 100x will focus - no harm in trying. It will be pretty inconvenient, though, if you have different "parfocal length" objectives on your microscope - and the chances of a lens or specimen-damaging error go up.

[Tom Jones]

Judge,

So far, this doesn't make much sense. If you hit the slide, the stop is not the problem. The stop is there to keep you from hitting the slide.

This isn't always as easy as it seems to be, particularly if you're on your own with no one next to you to ask. On-line troubleshooting things like this can be very difficult for folks with very little experience. I've trained a lot of people. If you live in Southern California, I might be persuaded to come by and give you some in-person help. Barring that, see if there's a hospital lab tech or biology teacher nearby that would be willing to give you some help for a few minutes. I'm pretty sure there's a simple solution to this.

Is that picture of the same microscope model? You say it hits on the "longer objectives". Is that one or two? What specimen are you trying to look at? If it's thin and hard to see, you could be just missing it.

Start by trying to focus on the very edge of the slide label (or coverslip). The edge makes it easy to see what you're doing. I actually do that a lot for very thin, transparent specimens. Then move to where the specimen should be and search without adjusting focus. Only adjust fine focus after you can see the specimen, otherwise you might move the plane of focus too far away to see the specimen. If you can't get the edge into focus, there are other problems that will probably need to have someone get their hands on the microscope to figure out.

At the higher magnifications the distance where you can see the specimen gets very shallow. The higher the mag, the shallower the depth of focus. If you miss focus it's pretty easy to keep on trying until you hit the slide/coverslip, or get way too high if you're going the other way. All microscopes have an awful lot of focus movement available in relation to the actual focus depth of even the lowest power objective. Starting at the lowest mag, the next higher magnification should be in focus within a full turn of the fine focus knob in either direction, probably less. The same for the next one up.

Objectives aren't always centered the same. Your specimen could be just out of the field on the next higher mag and you need to search for it.

Depending on the mag and the specimen you could be using too much light, strange as it seems. Use just enough light to see what you need to see. Too much can wash out all the contrast and make it invisible.

Then there's YouTube. If you search for "focusing a microscope" you will find quite a few more videos.

https://www.youtube.com/watch?v=GeHd0VMeDOs
https://www.youtube.com/watch?v=zzamomqlwxU
https://www.youtube.com/watch?v=Txx2BRtDn4Y

Tom

[Judge]

Thanks for your suggestions. I'll check out your recommendations. When I adjusted the stop for the higher magnifications I was unable the focus the lower objectives so I put it back to the original. Thanks again.