Such a dark field stop for filter holders with a diameter of 26.5mm is for sale. The ring diaphragm offers an inexpensive option for dark field microscopy up to a magnification of 40x and a numerical aperture of up to around 0.7. The aperture comes from the 3D printer and you can see that - but it works perfectly, is very stable and can no longer be seen in the filter holder anyway.

If the alignment is not exactly in the middle, oblique lighting can also be achieved to a limited extent - but the apertures for oblique lighting from my offer achieve better results.

You are always invited to take a look at the offer in advance in 08525 Plauen. In order to exclude any doubts and misunderstandings, this is expressly desired! The purchase amount is to be paid in cash upon collection or in advance by Paypal or bank transfer. Subsequent negotiations are excluded, since every interested party had the opportunity to inspect the offer.