Question about Tasco 750 Monocular Microscope

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Problems with viewing under low magnification (20x) only red stain

I was looking at cells under low magnification (20X) and noticed that
if I tried to view my stain on these-- dapi, rhodamine; the dapi worked
fine,light seemed to be aligned correctly. However, the red stain did not
show. It appears the light path is blocked -with two circles meeting half
way cancelling each other. This only happens and is the most obvious under
low magnification and with the red stain. If I try to view this with 60X,
I am able to get some of the red, however, you also see a halo - a part of
the field of view with bright light coming through. This is just a recent
development as I had no such problem last week.

So, my question to you, what could be causing this and how can I fix
Any help or advice would be greatly appreciated.

Thank you so much for you time.

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Sounds like you are using a Phase Contrast Microscope to me, and if this is the case, you will get just this kind of result, especially if it is not set-up correctly.
Let me have the make and model, and I will happily talk you through this one.

Kind Regards......Dave

Posted on Mar 10, 2008

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For the red colour partical your illumination angle should be 0 degree.
As per you exepirience you are getting red at low magnification and not getting at high magnification. at the higer magnification the light deviation you can apriciate more then lower.

try to adjust your light source focusing lenc at higher magnification so at the lower it will be more better,

for the further problem you can contect me any time,



Posted on Feb 20, 2008


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1 Answer

What would be the best spotting scope Under $200?

Celestron Ultima 80 Spotting Scope

This economical device is genuinely popular on the market. It is a large aperture spotting scope affordable for everyone. It needs more cost for a conventional 60mm scope. It is helpful in poor lighting conditions. They are great for long-distance viewing. You can use it in twilight or under heavily overcast skies.
The zooming lens of this scope is capable of zooming from a mere 20X up to a massive 60X magnification. You can easily handle it. The zooming knob is very smooth. It has large 80mm objective lens. It gives you over 77% more light grasp than a conventional 60mm scope. It has built-in 80mm objective lens are outstanding for light gathering.
It is a refactor-type scope. The achromatic objective lens used in this scope. The product comes built with quality materials. It has outstanding light transmission capabilities. Enhancement of brightness becomes easy. It also increases the clarity of the spotting. This scope is a well-built device. It can be used efficiently in rugged conditions. The device's rugged nature makes it a perfect thing in all circumstances. It is waterproof too.

Mar 07, 2018 | The Optics

2 Answers

What is the other types of microscope ? how do they differ from a compound microscope ?

Compound Microscope
  • Compound microscopes can be found in most biology and science classrooms. They are electrically operated and use light to enhance the image of a cell. They will have multiple lenses for viewing.
Dissecting Microscope
  • Dissecting microscopes are also known as stereo microscopes. They have low magnification and are also light powered. These microscopes can view objects larger than what a compound microscope is able to handle, in three dimensions.
  • A Scanning Electron Microscope uses electrons instead of light to create an image. These microscopes produce three-dimensional images with high resolution and magnification. They also have a larger depth of focus.
  • Transmission Electron Microscopes use electrons instead of light to create an image. The material prepared must be very thin. The beams of electrons that pass through it give the viewer high magnification and resolution. These give two-dimensional images.

Jul 03, 2011 | Computers & Internet

1 Answer

Using a digital camara on an Axioskop which has operated successfully in the past, I get an intense sphere of light. Th camera is mounted on an adapter, as before, but I wonder if there is a lens missing...

Generally speaking, without knowing much exactly what you have, there is a possibility that you could be missing a lens. It is hard to say though without asking you a 100 questions. The lens cell in front of the camera is designed to shrink down the square sensor of the camera, so that it can fit with in the round hole of the optics. Most adapters Will have several lens, which will depend greatly on the size of the sensor or how much it need to reduce it by. If there are no lenses then it would look like the camera is looking down a tube, and there will be shadowing or darkness all the way around your image.

If a single lens is missing then you would most likely get a sphere on light or very intense hot spot in the center of the field of view. It is really hard to describe what this would look like, but if you where able to see an image through it, it would appear to be bowed. With a photo, I could tell you for sure.

There are also other variables unrelated to the camera and adapter that might causes this, such has the position of the condenser (try adjusting the height), or you can also control this a bit by adjusting your iris. If this only occurs on the higher magnification, do you notice any changes in through the eyepieces. Sometimes if immersion old gets inside of one, it can act like an additional lens, and do all sort of crazy things.

When trouble shooting you need to determine which variables are at play. For instance do you only see it on one magnification, or is it only on low and not high. Is the hot spot seen through only the camera, or can you see if through the eyepieces as well? Each one of those question will help you start to isolate down where the problem is.

For instance if you know that it occurs on all magnifications, then you know you can rule out the objectives as the problems. If you can see it through both the eyepieces and camera, then you can rule out the camera and the adapter. If seen at higher magnification and not lower, than it is most likely not a condenser problem.

If you see it at lower magnifications then it could be several problems, but try to eliminate some of the variables at play. If you can answer some of the above questions for me, I might be able to guide you in a bit better direction.

Good luck!

Jan 31, 2011 | Zeiss Microscope

2 Answers

How do I increase the field of view on a zeiss OpMi-1?

Field of view and working distance vs magnification is a law of physics. Using the lowest power gives you the widest field of view and greatest working distance but the trade of is that you loose magnification. Conversely as you increase magnification you decrease working distance and you loose field of view diameter.
The optics of your microscope are limited to .4x to 2.5x magnification. Your working distance is limited to 200 - 400mm depending on the magnification you are using.
I am not aware of any interchangeable lenses for this scope.

Nov 28, 2010 | Zeiss Microscope

2 Answers

How to determine the lowest possible usable magnification for a telescope

Don't confuse low power with WIDE field. Usually to get the lowest power and widest field you need to move to a 2 inch eyepiece, and a 2 inch diagonal.

About 38-42mm eyepiece will be the lowest power. Take a look at the GSO Superview 2 inch eyepieces, which yield a wider view. and low power.

Oct 29, 2010 | Celestron CPC 925 XLT (555 x 235mm)...

1 Answer

Can not seem to focus when we look through the lens we just see the bk=lack sky we cannot seem to see anything

try this:
see the mini scope on top of the telescope?--that's called the finder scope--
you look through that to see what the telescope is aimed at, just like what a sniper does before he pulls the trigger.

put in the lowest power eyepiece you have in the telescope, the one with a high number on it.

it's a good idea to align the 'finder' with the telescope during the day time--it's much easier.

if your telescope and finder scope aren't aligned properly, aiming your telescope at any target will be off and you'll just get frustrated.
to do this, look through your finder scope and pick a far away target, put in the lowest power eyepiece you have, that's the one with a high number--
high number = low power = a nice big view in the telescope.
low number on eyepiece = high magnification, like a zoom lens.

always use the lowest eyepiece first, then work your way to higher magnification, if you want to get a closer look at your target.

use lowest power eyepiece in telescope--> look through finder scope -->focus the image--> switch to higher power of eyepiece for a closer look at your target.

practice this during the day until you're comfortable, then try it at night.
try the moon, it's a nice big target

you can also use binoculars to check out the night sky.
you can try using 7x35 or 7x50 binoculars.
you see a lot more stars and it gives nice big views of the stars and constellations...and the moon...

hope this helps :D

Jul 30, 2009 | Bushnell Deep Space 78-9512 (120 x 60mm)...

2 Answers

Black spot in the center of the image viewed in telescope

If this is a Newtonian reflector or a catadioptric scope (Schmidt Cassegrain or Maksutov) you may be trying to use it at too low of a magnification. Your magnification needs to be high enough that the exit pupil is less than 5 mm; to figure this divide the focal length of the eyepiece by the f-ratio of the optical tube. If this quotient is 5 mm or more the black spot you are seeing is the shadow of the secondary mirror.

Dec 14, 2008 | Celestron NexStar 5 SE (300 x 44.45mm)...

2 Answers

Can stained bacteria be seen with a 40x magnification microscope? not in detail, just enough to determine coloration of individual bacteria

Hello--I understand that you need at least 600x to view bacteria and some say 1500+ so 40x doesn't seem to be in the right mag. area at all--not sure this helps much.You could purchase a 100x obj. and 10/15x eyepieces but will probably be into oil immersion for the obj.Possibly a 20x eyepiece + a 60x obj will give you a degree of definition.I use a SEBEN Bino with this combi and it gives a small view but not good.kind regards martin r

Nov 13, 2008 | National Optical 131 Monocular Microscope

6 Answers


Hi there,

Seing bacteria isn't just about magnification, many
are transparent and need to be stained. Even at X1000, you will see little detail, but can make approximations of shape etc. Here is a good starting point for staining bacteria.
With a toothpick scrape a little plaque from your teeth (size of a pinhead is plenty). Put this in the centre of a slide with 1 drop of water and mix thoroughly. Allow this to dry then pass the sample through a flame three or four times (hot, but not hot enough to burn fingers) Stain for five mins using either Methylene Blue or Eosin. If you don’t have these, Blue or Red fountain pen ink will do for starters. Rinse off excess stain with very slow running water. Blot dry and observe at X400. If you have an oil immersion lens, you must use a cover slip and mount your specimen in balsam first.
If I can be of any further help, please don’t hesitate to ask.

Aug 01, 2007 | National Optical 131 Monocular Microscope

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