This is my first time posting and hope to learn a lot here! I just got a new to me Standard 16 with Neoflaur phase objectives. I used that for teaching and had started taking pictures with the trinoc head with an Amscope 2x adapter. However, with the pictures I took with the 10x objective, there seems to be a patch of dirt (see picture). I thought I wiped down the adapter lenses, objective, condenser lenses, and also the field diaphragm part... so I am bit puzzled as to where there might come from... any suggestions? Thank you!
