Filter Holder Modification. (Darkfield Oblique)

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Roldorf
Posts: 341
Joined: Tue Apr 23, 2019 6:58 pm
Location: Northern Germany

Filter Holder Modification. (Darkfield Oblique)

#1 Post by Roldorf » Sat Aug 17, 2019 11:47 am

I have found that my filter holder is a little difficult to use (to put it mildly). It involves removing the filter holder from underneath the condenser inserting the filter then fiddling it back into the condenser. A solution was required!!
I decided that a swing out filter holder would be the best, so with the materials I had at hand (some 5mm white perspex and a steel rule) I measured the bottom of the condenser and started to cut out some pieces.
Image

I eventually ended up with this cobbled together holder:-

Image

The holder swings out so you can change filters, the one you see is a dark-field that I had made when i first got the scope.

Unfortunately the perspex transmitted far too much light and scattered it all over the place.
This was solved with the help of a black permanent marker late this morning which I used to 'paint over' the parts that were transmitting the light, an inelegant but quick and workable solution.
That solved the problem of the scattered light but I wasn't achieving dark-field. A slight mis-measurement meant that the filter holder (what could I have expected using a 500mm steel rule and a three meter tape) didn't quite go far enough in to properly centralize the stop.

Re-drilling the position of the screw for the swivel made the difference, however it went a little 'too' far, necessitating a little to and fro with the new holder.

Great things are discovered by accident. I noticed that this to and fro also gave me oblique illumination and although I don't get dark-field at 40x and 60x, I do get oblique at those objective's.

The next pictures are some quick and 'dirty' images of those results.
No editing other than the added text in Photoshop, just as they came from the camera.

10x
Image

40x

Image


60x

Image


The final mounting looks like this (showing the holder part way slid in).


Image
Alan
Bresser Science Infinity 4x 10x 40x 60x 100x oil. Canon EOS 4000d
Optika SFX 90

tgss
Posts: 87
Joined: Wed Jan 25, 2017 3:48 am
Location: Ontario, Canada

Re: Filter Holder Modification. (Darkfield Oblique)

#2 Post by tgss » Sat Aug 17, 2019 5:57 pm

Good job Alan... actually very good job considering the vast array of tooling you had at your disposal :lol: And as you have shown, you never know what little bonus (oblique) fate will bring your way if you only try!
Tom W.

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