PHOTOMETER INSTRUCTIONS

1. Mark plate as model plate with N,S,E,W, and circle around the cluster on back (glass side!) of the plate.
Insert carefully, emulsion side down, north pointing towards you in the plate carrier.

2. Turn switch on gray box on (3 hours before using).

3. Turn oscilloscope on

4. Turn bottom switches on photometer on (3 hours before using)

a) projection lamp

b) mains

c) scale illumination

5. Turn off all room lights

6. Set brightest star of the cluster into center of iris diaphragm in turning the large inner knobs at right and left of the photometer.

7. Focus on image in diaphragm with outer smaller knob on the right of the photometer.

If no focus (sharp grain) is found, get help from Mrs. J. [She will turn small knob on left (back of the two knobs mentioned before) which should otherwise not be touched. It changes the magnification. In addition to it she may regulate the position of the objective of the microscope near the plate].

8. Close diaphragm with small outer knob on left hand side until a small rim is left around the brightest star of the cluster.

9. Set the wedge with the small knob on the right side of the photometer back of the two knobs and regulate until the reading on the oscilloscope passes through a "zero" position.

10. If the oscilloscope figure is too wide or too narrow, too long or too short, regulate with horizontal and vertical gain knobs on oscilloscope.

11. If oscilloscope figure changes too slowly or too rapidly (no steady figure) turn knob "sensibility" on front side of photometer.

12. Now set faintest star of the cluster into iris diaphragm when wide open, then close diaphragm until "zero" reading on oscilloscope, compare reading of the iris setting with that of the bright star. These should be a difference of at least 15-20, better more, on the scale. If not start again at p. 6) and make the rim around the star in p. 8) smaller than before.

13. Start measuring the stars, always centering first with diaphragm wide open, then focus, then make fine centering with smaller diaphragm.
Take reading of diaphragm setting when "zero" reading on oscilloscope.

X — X

Plot reading of diaphragm on X-axis and magnitude from Miane's paper on Y-axis.