Floaters

[wmodavis]

I now have a working microscope by piecing together a couple of ebay buys. Hurrah!
I'm working on my BASIC microscope skills and have quite a long way to go but am having fun.

Here's one frustration I've experienced that possibly I'm not the only one to have noticed. It is more likely a problem with my eyes than the microscope.
It is most noticeable using the 100x objective.
The frustrating problem is: Way Too Many interfering floaters drifting around obscuring my view.
Anyone else experiencing this and if so are there any possible remedies?

[75RR]

Changing the viewing distance and/or the angle of view sometimes helps.
Not sure is certain eyepieces are more prone to this or not.

[wmodavis]

Well besides the floaters I've observed some despicably dirty objectives. But that is another problem. The floaters aren't too objectional on the 4x & the 10x. Changing the viewing distance and/or the angle of view moves them around but doesn't seem to affect their number or obtrusiveness.

[apatientspider]

As a general rule floaters are in the eyes themselves. Using a binocular microscope will minimize them. Also, use a scope that has its eyetubes inclined toward you at an angle so that you don't have to look straight down or lean over it - or tilt the scope; most binoculars have inclined tubes these days. One last suggestion is to look away from the microscope, tilt your head back, and roll your eyes periodically. If they are really, really bad, perhaps you should see a doctor. That's all I've got - hope it helps.

Jim

[gekko]

My 2 cents' worth: I think the narrower the angle of the light cone, the more visible/objectionable the floaters. Make sure you adjust the condenser height (all the way to the top, or if you have Koehler illumination, set it correctly), and also try to have the condenser iris not set too small. I also find that when I am tired, the floaters seem to bother me more.

[wmodavis]

Jim -I have an Olympus BH-2 trinocular with inclined eyetubes. I'll try some of the other ideas you mentioned. I did think of seeing the eye doctor.

gekko - I'm using correct Koehler setup but the way I understand to do it has the condenser iris nearly closed and condenser nearly to top position. Here's my procedure
1 - Open both condenser and field iris.
2 - Focus scope on specimen
3 - Move condenser to top
4 - Reduce field iris to view edges of iris
5 - Adjust condenser height til field iris is in focus
6 - Increase field iris to field of view +
7 - Set condenser to objective NA or for best contrast.
8 - Set brightness with illuminator dimmer

Any other suggestions. Could be tired eyes I'll admit that.

Maybe immersion oil in my eye?

[gekko]

Bill, your procedure for obtaining Koehler illumination is the way I do it. However, when you say, the way I understand to do it has the condenser iris nearly closed, I am puzzled. This may be almost true for a 4x objective but not for higher powers. What I do is remove the eyepiece and look down at the objective aperture, then adjust the condenser aperture to almost fully illuminate the objective, then tweak it for optimum contrast/resolution. I assume that is about what you are doing too. Closing the condenser too much will accentuate the floaters (as well as result in poor images). Not a good idea to pour immersion oil in your eyes nor into the back of the objective .

[merrimoles]

What you're seeing is not unusual. A combination of high mag and a condenser iris that's closed some way down results in this. What you're seeing is specks of dust on the surface of the eye. I don't know why these become visible under these circumstances, but I see them too.

A true floater is a clump of protein contained within the eye's vitreous humor. It casts a shadow on the retina and appears as a darkish spot that moves around in your field of vision. I have one in my left eye, courtesy of a slip on the ice and a bang on the head. If you don't see these spots when you're NOT looking into a microscope, then I don't believe you have floaters. If you do see them when not looking down a microscope, then you should get your eyes checked. Although usually benign, and common amongst older people, they could indicate a problem in the eye.

[wmodavis]

Gecko - That brings up a good point. When I follow the steps I listed I invariably and even on 100x end up with the condenser iris nearly closed. Now from my reading I expected best resolution to occur somewhere around where the condenser setting matched the NA of the lense being used. I only have a 4x, a 10x and a 100x. With the 4 & 10 the condenser is approx @ the lense NA but not with the 100. If I set the condenser to the 1.25 NA that appears on the 100x lense it is washed out very bright and virtually no detail. Only when I stop it down to near minimum is there good contrast and detail. Sounds backward to me. What am I doing wrong. I will hold off on trying the Type A oil in my eyes.

Mirrimoles - I do see floaters most of the time but usually they are unobtrusive and I really have to pay attention to see them. They just seem to really jump out when I'm looking into the scope and they are very distracting when using the 100x as that's when they seem most noticeable. And my floaters are not just spots but many or most (I haven't counted) are long skinny lines mote like a curly hair rather than a speck of dust. I might see the doc on that. Wonder if they can do something about it besides charge me money. I do fit the category of older.

[gekko]

Forgive me for beating a dead horse, but perhaps you might try actually looking at the back focal plane of the objective to ascertain the condenser aperture adjustment. The calibration on the condenser itself may not be sufficiently reliable. Another rough, quick way is to open the condenser iris all the way, then slowly close it until you see a slight reduction in the light level.

[75RR]

Another rough, quick way is to open the condenser iris all the way, then slowly close it until you see a slight reduction in the light level.

That is the method I use. It is the one Zeiss recommend on their site.

The interactive tutorial is both useful and fun!
Note: Remember to start by aligning the filament first.

http://zeiss-campus.magnet.fsu.edu/tuto ... flash.html

[wmodavis]

Thanks again guys.

75RR - That article was very helpful and went along with the recommendation of 'dead horse beating gekko' and helped clarify some other things for me as well.
It seems that removing the eyepiece and looking as I close down the condenser aperture and normally viewing the specimen through the eyepieces as I close it down achieves roughly the same thing. And that was what I was doing in my step 7 above though not as clearly explained.

I'd hate to be trying to learn to use this scope without a bunch of helpful experts sitting at my elbow chiming in. It is appreciated.