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PostPosted: Fri Jan 11, 2019 5:03 pm 
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Is there an aftermarket device (or home engineered one) that extends the radius of the fine focus knob for very fine increments of the focal plane?
Should be good to use for image stacking software.
The knob on my microscope has a small radius and its difficult to focus on higher magnifications.

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PostPosted: Fri Jan 11, 2019 7:00 pm 
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You should be able to focus sharply with your microscope's fine focus.

Two things that might be preventing you would be too much water under the cover slip or the cover slip itself may be too thick.

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PostPosted: Fri Jan 11, 2019 7:49 pm 
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The precision of fine focus mechanisms on microscopes varies quite a bit; anywhere from 1 micron to 2.5 microns as marked in graduations on the focus control or knob. Small knobs will provide less control, with wider graduations between the marks. If your microscope has a smaller knob and less precision , it may be because the mechanism cannot support finer control. The best you could do is retrofit it to larger knobs with finer graduations but that would be a bit of a job.
Many people doing stacking, buy a used focusing block from a fine instrument and use that for their increment control.


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PostPosted: Fri Jan 11, 2019 8:03 pm 
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lperepol wrote:
Is there an aftermarket device (or home engineered one) that extends the radius of the fine focus knob for very fine increments of the focal plane?
Should be good to use for image stacking software.
The knob on my microscope has a small radius and its difficult to focus on higher magnifications.
I doubt that an extension of the radius of the focus knob will improve stacking. I tried but failed to find the vertical travel range of the Omax microscope. But on other compound microscopes, the travel range is typically a few millimeters and the vertical focus scale marks are spaced at around 1-2 micrometers. Very probably, the same range and spacing holds for the Omax as it comes, with the original focusing knob. Such spacings should suffice for stacking, considering that the vertical resolution of even the best objective is about 0.5 micrometers.

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Last edited by Hobbyst46 on Fri Jan 11, 2019 9:10 pm, edited 1 time in total.

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PostPosted: Fri Jan 11, 2019 8:21 pm 
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This may be of interest:
https://www.pc-control.co.uk/control/articles/article13.php

MichaelG.

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PostPosted: Fri Jan 11, 2019 8:51 pm 
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Quote:
Is there an aftermarket device (or home engineered one) that extends the radius of the fine focus knob for very fine increments of the focal plane?


There certainly is. Between 'stiction' and the small size of the knob, it is sometimes desirable to have an aid in incrementing the knob, as for focus stacking. Here's what I do:

Say for example your fine focus knob is about 1/2" (12mm) in diameter. Get two pieces of wood or plastic, each about 10" (250mm) long and 3/8" square (sort of like a couple of long chopsticks). Fasten them together at one end with string, wire, or tape so that they are about 1/2" apart there, but are tied together pretty well. Put this arrangement over the knob and down near where the sticks are tied together. So now you see that if you squeeze the other end of the sticks together, they will squeeze the fine focus knob like a nut in a nutcracker. Put a rubber band over the two sticks to hold them on the knob. To change focus, just squeeze lightly and rotate the end of the two sticks (and thus the fine focus knob) through an arc the desired amount. For focus stacking, use a small increment, e.g., move the end of the sticks about 5mm or so, take an exposure, move again, etc. You could even set up a piece of cardboard behind the sticks with an arc pre-divided into increments.


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PostPosted: Fri Jan 11, 2019 8:58 pm 
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Thanks wporter.

That is a great and simple innovation!!!!!!!!!!!!!

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PostPosted: Fri Jan 11, 2019 9:24 pm 
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MichaelG. wrote:
If it were easy to define the specs of appropriate stepper motor to rotate the knob, ANDIF Canon Camera were providing a software tool for remote firing of the shutter, like a tool that communicates with Mathlab, a project of "automatic Z-Stacks for all" could be realized...

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PostPosted: Sat Jan 12, 2019 8:52 am 
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Hobbyst46 wrote:
MichaelG. wrote:
If it were easy to define the specs of appropriate stepper motor to rotate the knob, ANDIF Canon Camera were providing a software tool for remote firing of the shutter, like a tool that communicates with Mathlab, a project of "automatic Z-Stacks for all" could be realized...



Sounds like you are describing the Micromate with its controller:

https://www.wemacro.com/?product=micromate

Image


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PostPosted: Sat Jan 12, 2019 9:34 am 
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Thanks, Viktor, for the link!

Good to know that the device exists, and it does what I thought about!
It looks as developed for new inexpensive microscopes, but probably will work for any microscope.
The price appears fair, considering that it is a complete package.

I am not sure about the mechanical aspects, namely, how stable is the holder, how reliable is the coupling to the fine focus knob, how does the device handle internal friction in the microscope focusing knob, how does the user secure exact co-linearity of the focusing knob and rotation mechanism - motor axis, motor on the stand, and is it possible to override the motorized focusing, and apply manual focusing, without removal of the grip.

Obviously, the device cannot trigger the shutter of the Canon EOS mirrorless camera; but this is due to the lack of such option on the camera itself. I really think that Canon should have done better with their line of EOS-M cameras. there are basic unjustified (IMHO) shortcomings in this line...

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PostPosted: Sat Jan 12, 2019 9:45 am 
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Hobbyst46 wrote:
... how does the user secure exact co-linearity of the focusing knob and rotation mechanism - motor axis, motor on the stand etc ...

The purpose of the slit flexible coupling, is to avoid the need for exact co-linearity.

MichaelG.

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PostPosted: Sat Jan 12, 2019 1:01 pm 
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Thanks MichaelG for the clarification. The flexible slit coupling is new to me.

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PostPosted: Sat Jan 12, 2019 1:07 pm 
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I haven't tried it myself, but several at photomacrography.net forum seems happy with it. Some have used it as a foundation for further DIY adaptations. William's (Wemacro) stacking equipment is very well regarded in the photomacrography community.


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PostPosted: Sat Jan 12, 2019 1:21 pm 
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Hobbyst46 wrote:
Thanks MichaelG for the clarification. The flexible slit coupling is new to me.

Here is one example:
https://www.omc-stepperonline.com/635mm-8mm-flexible-coupling-18x25mm-cnc-stepper-motor-shaft-coupler-st-fc06.html?search=coupling
This version has a single helical slit ... others are available with alternate half-slits.

VERY useful things !!

MichaelG.

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PostPosted: Sat Jan 12, 2019 2:43 pm 
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MichaelG. wrote:
Hobbyst46 wrote:
Thanks MichaelG for the clarification. The flexible slit coupling is new to me.

Here is one example:
https://www.omc-stepperonline.com/635mm-8mm-flexible-coupling-18x25mm-cnc-stepper-motor-shaft-coupler-st-fc06.html?search=coupling
This version has a single helical slit ... others are available with alternate half-slits.

VERY useful things !!

MichaelG.
You are definitely reading my mind! Pay $179 for that stacking device??
In addition to the coupling we need a low RPM, high torque stepper motor. 200 steps/revolution would suffice IMO. Please note that I do not speak NI's Labview. And have no mill. For connection to the focusing knob - perhaps a lens/filter holder from Oriel, with set screws (from the junk drawer). Motor holder and stand - just flat metal slabs or LEGO parts. A specific challenge is the electromagnetic small arm to "press" onto the camera LCD screen and remotely fire the shutter. I am working on it right now.Fist find - it must be a warm tip of something.

viktor j nilsson wrote:
I haven't tried it myself, but several at photomacrography.net forum seems happy with it. Some have used it as a foundation for further DIY adaptations. William's (Wemacro) stacking equipment is very well regarded in the photomacrography community.
yes, there is a running thread post about it right now. Thanks.

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PostPosted: Sun Jan 13, 2019 9:12 am 
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The direct coupling between knob movement and table movement is not of the same quality on all microscopes.
Perfect fine focus movement is a sign of a high quality microscope in optimal serviced condition. I don't think that Omax is in the top region of the market here. So it might be of limited use to optimize the knob movement because the table doesn't follow these fine increments.


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PostPosted: Sun Jan 13, 2019 12:15 pm 
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Hi, I don't know much about the mechanics of stacking although I do routinely use shallow-stacking, both in terms of number of images stacked and total depth over which they are stacked. With transparent and/or translucent subjects such as slides and indeed 'critters' I have a question that is naive and maybe even stupid.

The assumption/presumption that stacking intervals are optimally equal - is this actually the case? When I stack I choose points that I would like to use as 'waypoints' to use as my focal levels, rather than stack at regular (1ยต in the case of the Orthoplan's fine-focus) intervals?

Any thoughts, examples. This is a very interesting thread, thanks all for the contributions, apologies that I haven't much to say, only to watch.

John B.

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