Don't use histogram equalization. It's a common beginner misconception that it helps. It is not needed.
First of all, it usually produces weird, unnatural looking images. If you want more natural images, use imadjust instead. It produces a linear remapping of gray levels.
Secondly, it doesn't help at all in segmentation. All it does is rearrange the gray levels to new values, essentially stretching the histogram in a non-linear way. That will absolutely not help in segmentation by thresholding. All it does is change the gray level that you select for the threshold. It will not make the thresholded binary image any different.
