You are observing a slide of green cells under the 4X objective. Each cell covers roughly 1/8th of the width of your field of view. How large of a diameter do these cells have?

The equation I found is:

Size of cell= field diameter/ # of cells that fit across field

So the objective is 4X then the field diameter is 4,500 micrometer... but I can't figure out the number of cells that fit across the field...Is it impossible to estimate this?

562.5

To estimate the number of cells that fit across the field, you need to know two things: the field diameter and the width of each cell.

In this case, you have the field diameter, which is 4,500 micrometers. However, you mentioned that each cell covers roughly 1/8th of the width of your field of view, but you didn't provide the actual width. Without this information, it is not possible to estimate the number of cells that fit across the field accurately.

To get an accurate estimate, you need to measure or obtain the width of each cell. Once you have this information, you can use the equation you found:

Size of cell = field diameter / number of cells that fit across the field.

By substituting the known values, including the width of each cell, you can calculate the size of each cell accurately.

Therefore, without the width of each cell, it is impossible to estimate the diameter of the green cells you observed on the slide.