Which are the main features of a microscope?

Before buying a microscope, it's important to keep in mind the following characteristics:
- MAGNIFICATION: the product of eyepiece magnification and lens magnification gives the total magnification power. An increased magnification decreases the field of vision.
- ILLUMINATION: it may be either incident light, meaning from below and particularly useful in a biological microscope, or transmitted light, meaning from above and for a stereoscopic microscope. Some stereoscopic models have both types of illumination. 
 
Which are the optional accessories recommended for a microscope? 

According to client's needs, in order to increase or decrease the magnification provided, it could be necessary to purchase extra eyepieces and/or lenses.
In a biological microscope, when it isn't included, a small transport table (a square-shaped instrument that allows microscopic movements of the glass plate) and a light to provide the necessary lighting in the observation of the prepared slides, could be useful.
A special graduated micrometric eyepiece could also be useful, in order to measure exactly the dimensions of the prepared slides 
 
Can a camera be connected to a microscope? 

Yes, but two adapters are necessary: the photo adapter for a given microscope and the T-2 ring for the type of reflex. On a binocular microscope the camera is connected to one of the two eyepieces. 
 
Is it always necessary to prepare the items for the observation at the microscope ?  

Using a stereoscopic microscope, whatever is viewed doesn't need preparation. Instead, using a biological microscope, it's necessary to make accurate preparations. The sample must be cut very thin and it must be placed on a glass slide. It could seem a rather complicated process, so if you don't want to do it yourself, Konus has in stock more than 20 series of prepared slides with interesting biological subjects.