Question?

[InstantMochiii]

So I was trying the use the 40x objective and it would only show white... But then it worked after I moved the coarse focusing. The objective is literally touching the coverslip though, is that normal? Are objectives usually supposed to touch the coverslips? With 4x and 10x I didn't need to touch the coverslip, but with 40x it appears that I do...

[75RR]

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In general, the higher the magnification the closer to the cover slip the objective tends to be.

Always work up to the maximum magnification, i.e. start with your 4x (good to scan the cover slip and get an overall of view of things), then move up to 10x, then the 20x if you have one, followed by the 40x ...

One you are at 10x it is best to only use the fine focus, using the course focus with medium and hi power objectives is how you break cover slips!

Make sure you do not have too much water under the cover slip. https://www.youtube.com/watch?v=yxTFgDe5CEE

[dtsh]

To add to what 75RR said, as magnification goes up the working distance tends to go down. With higher power objectives it's possible to have media that's too thick to view all the way to the bottom of the specimen. I have some slides of ticks which are troublesome with the 100x oil as the specimen and coverslip are thicker than the objective's depth of focus.

This also becomes an issue with some other slides, such as a haemocytometer or a McMaster slide, where the "cover slip" is 0.4mm and 1.0mm respectively, which means that many high power objectives just can't be used as they can't focus far enough down to get past the coverslip (or media, if the subject sank down in the media). As I understand it, this is the reson one adhere's subjects to the coverslip rather than to the slide so that more of it is wihin reach of more objectives.

[InstantMochiii]

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In general, the higher the magnification the closer to the cover slip the objective tends to be.

Always work up to the maximum magnification, i.e. start with your 4x (good to scan the cover slip and get an overall of view of things), then move up to 10x, then the 20x if you have one, followed by the 40x ...

One you are at 10x it is best to only use the fine focus, using the course focus with medium and hi power objectives is how you break cover slips!

Make sure you do not have too much water under the cover slip. https://www.youtube.com/watch?v=yxTFgDe5CEE

I didn't know that I had to make sure I didn't have too much water under the microscope and was under the impression that I had to have as much as possible, haha. I'm guessing that's the reason, why... I'll have to try to control it more and also refer to the video you've linked! Thank you~ XD

[BramHuntingNematodes]

If you are using a concave slide, it may not be possible to focus on some things at the bottom of the concavity.

I have a 47.5x that has an adjustment collar for different coverslip thicknesses, and even then the useful range is still give or take a tenth of a millimeter

[InstantMochiii]

To add to what 75RR said, as magnification goes up the working distance tends to go down. With higher power objectives it's possible to have media that's too thick to view all the way to the bottom of the specimen. I have some slides of ticks which are troublesome with the 100x oil as the specimen and coverslip are thicker than the objective's depth of focus.

This also becomes an issue with some other slides, such as a haemocytometer or a McMaster slide, where the "cover slip" is 0.4mm and 1.0mm respectively, which means that many high power objectives just can't be used as they can't focus far enough down to get past the coverslip (or media, if the subject sank down in the media). As I understand it, this is the reson one adhere's subjects to the coverslip rather than to the slide so that more of it is wihin reach of more objectives.

Ohhh, that actually makes a lot of sense. So basically, if the specimen is too thick then the higher-powered objectives can't really "reach" the view of the specimen. That's interesting. Thank you! XD

[InstantMochiii]

If you are using a concave slide, it may not be possible to focus on some things at the bottom of the concavity.

I have a 47.5x that has an adjustment collar for different coverslip thicknesses, and even then the useful range is still give or take a tenth of a millimeter

Ohhh, I see, that's cool! I'm not using a concave slide as of now, but this did help! Thank you~!

[DonSchaeffer]

You can take some steps. First of all, flatten your specimen. Sometimes the specimen is too thick. Press down on the cover glass to make sure the specimen is a thin as possible. I have even made the mistake of putting the slide in with cover glass laying on the stage and wondering why I can't focus. You can also get thinner cover glasses. The high power objectives are a joy. Don't deny yourself their use.