Re: Q: "crosshair" slide function - vernier?

J. J. is correct and I would like to expand the information..

Zeiss rotating microscope stages were used on microscopes configured
for petrographic studies of thin rock sections and crystal specimen.
These stages not have centering adjustments. Instead the polarized
light objectives have eccentric cams built into them by which the
optical axis of the microscope was centered over the stage..

The cross hair slide was placed on the stage and adjusted with the
mechanical stage (slide holder) until the center of the cross hairs
remained in a constant position as the stage was rotated. Then the
objective was adjusted so the cross hair was centered in the field of
view.as determined by an eyepiece with a similar cross hair.

Such alighnment enabled the user to measure the precise angles at
which a crystaline specimen changed colors in ploarized light. The
angle of rotation and other quantitative measurements provided
physical data for identifying the mineral being observed..

Aaron

On 20 Jan 2006 09:53:30 GMT, jjedwab@xxxxxxxxx (jacques jedwab) wrote:

>In article <1137725754.344702.73970@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
>"dr.mutaciones" <dr.mutaciones@xxxxxxxxx> wrote:
>
>> Hi, I have a slide from Zeiss that has a fine crosshair printed on it.
>> It says -
>> tisch-Nr ###, Vor der Tischzentrierung nonien auf 107.7 u. 12.80
>> stellen
>> Table number ###, Before centering the table, adjust to 107.7 - 12.80.
>>
>> Can you help me get at its use? Its at least 40 years old from the
>> dates on a calibration card.
>>
>> I'm guessing that it was used to calibrate the stage to accurately read
>> specimen position with the vernier scale??
>>
>> Thanks, Dave^
>
>This was probably used with a rotatable stage mounted on a petrography
>(polarizing) microscope. With research microscopes, one had a choice of
>removable stages (rectangular and circular).
>
>J.J.
.