Pinned specimen orientation

A forum to ask questions, post setups, and generally discuss anything having to do with photomacrography and photomicroscopy.

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elf
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Post by elf »

Only one surface needs to be spherical. The base can just be a cylinder. The big problem with this approach is getting to 90 degrees. You may need several units stacked together to do this.

Charles Krebs
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Post by Charles Krebs »

Barry,

I'm a big fan of the "compact, spherical" approach. In looking at your latest diagram, it think one thing needs to kept in mind. If the subject is something like a small fruit fly, then this approach would work OK. But if you have a subject like a fairly large, pinned grasshopper specimen, and you are interested in photographing just the "face", your subject areas will be considerably de-centered.

While I was being casual with my reply to Chris (I'd hate to see him get in an accident after prying off one of his cars blind-spot mirrors :wink:) , this is why I think a simple device needs to utilize some "preparer's input". A simple removable "jig" of some type can be placed on the platform that would indicate the center point. As the mounted subject is positioned in the putty or cork, the photographer can place the area of interest (and orient the desired "plane") at the center of movement. This would greatly diminish the need for greater range of movement of the device (as Elf has pointed out) since the photographer has "roughed in" his desired composition and should be able to fine-tune it within the degree of movement provided. This could all be accomplished more "elegantly" with a much more complex mechanism, but for most purposes I don't think it would be necessary.

Barry
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Post by Barry »

A grasshopper....I see the problem.
In such case, the mounting surface of the positioner could be flat, rather than concave. Now you can position the pin/base such that the grasshoppers' face is in the centre. But as you say, Charles: what is the centre?

One could find out when looking perpendicular to the flat surface, and the centre is indicated (through a little hole, see image). The other option is to have a separate indicator (see other image, the white part), which indicates the centre. But ofcourse, there will always be subjects where the indicator could be in the way (a butterfly with open wings).

(the transparent ball is to show where the actual centre is)

Cheers,
Barry
Image
Image
Image

Charles Krebs
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Post by Charles Krebs »

Barry,

Your third image is exactly what I meant when a mentioned a removable "jig". The "eye" is remarkably good at centering something when it has clear guides. Certainly one or two such "jigs" and a center mark the platform could work well for the vast majority of uses.

(hmmmm.... intrersecting laser beams.... :-k ... just kidding!)

ChrisR
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Post by ChrisR »

Add a clip - ... grasshopper face... :smt040
Image

elf
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Post by elf »

Here's one based on the magnetic toy and a ring from a rather large thrust bearing:
Image

Just need to add the pin and insect:)

If a gimbal mount were added we could call it a semi-universal stage...

p.s. The thrust bearings came from Boeing Surplus quite a few years ago for just a couple of dollars. Unfortunately they stopped selling to the general public a couple of years ago. Any large metal (ferrous) ring could be substituted.

ChrisR
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Post by ChrisR »

Clever! In a gimbal mount the horizontal ring would have to be a magnet, I think, to stop the vertical one falling over. I haven't seen "super-magnets" with the right sort of dimensions, but loudspeaker magnets are very much in the right range.
The specimen would certainly go round nicely in the ball race!

Barry
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Post by Barry »

So, in the toolkit, there should be a variety of specimen holders: magnet with fixed pin, magnet with clamp, magnet with chop of clay...

How large (diameter) would the platform have to be? And what angle of adjustment?
If interested, I could make some.

Cheers,
Barry

lauriek
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Post by lauriek »

I haven't chipped into this thread so far, too many good ideas already! However I just wanted to mention, Barry if you can make a few of one of these ideas then I'm definitely interested in one! :) Those goniometers are a bit pricey for me at the moment!

Are all of these insect pins made of steel? I'm wondering if this holder ends up with a big pin stuck in it (to place the bug at the center of rotation), could one of those tiny pins be stuck to the big pin with a couple of tiny but strong Neodymium magnets? something like these?

elf
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Post by elf »

Here's what the gimballed version could look like. It could easily be scaled up or down.

Image

Barry
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Post by Barry »

OK, will make some. (including that "jig").

How would 2" / 50mm be as diameter of the disc? Or smaller?

Cheers,
Barry

Graham Stabler
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Post by Graham Stabler »

I have made a few jigs using ball bearings and car body filler such as "Bondo" you grind a flat for your sample attachment, wax the ball and set in a lump of filler. You can cut the filler neatly with a rasor blade if you catch it just before it goes really hard, also a good time to loosen the ball a little. You can do the same with any ball, could be plastic or whatever.

Graham

ChrisR
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Post by ChrisR »

Barry - small disc for some folk probably. But then it would be jerky to move, so a handle like a frying pan's, perhaps 50 - 150mm long, would make small movements easier.
Or even two, or three...!

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ChrisR
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Post by ChrisR »

Another thought. With a horizontal setup the most difficult direction to adjust seems to be the Z, vertical. If the support tube in the above suggestions were two pieces with a screw thread between, I think it might be useful.

The world of plumbing just happens to have a wide range of sizes, in plastic and brass!
Brass as far as I can remember goes 4mm pipe to 159mm
and plastic commonly 22, 32, 40, 50, 110 and some other sizes.
There's iron as well, but probably less suitable.

ChrisR
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Post by ChrisR »

Rotating & X-Y base from a site survey theodilite (weighs 10lb/3kg) £20
Gimbals from a boat £4
Mini stage $25. For the other axis squeeze the Blu-Tack

Image

Is there a Tongue-in-cheek emoticon?

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