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Problem in spectrometer? - why is my telescope image inverted

People who have the experience during the spectrometer to find the angle of the prism and the angle of minimum deviation, I encounter the following problems. Please let me know how to solve this problem
1) First, make the first adjustment to the telescope pointing to the remote object to obtain a clear reflection in the field of vision to
2) Then, using a spirit level, I make sure my prism table in the horizontal plane
3) Now that have the telescope and collimator in accordance with the concept of the source of sodium mono-and Sharp only a thin slit in the middle of the crosshairs
4) Now, if the place of the prism to determine the angle of the prism, slit my well below the radar screen by the telescope to capture the image of the light source both the faces that reflect.
5) using the leveling screws on the bottom of the table, I prism of improving the image in the middle of the field of vision
6), but when I start to get the angle of minimum deviation, even the image of the visual field below the
Why this problem occurs? Please GIVSolution E of me ... Thanks in advance