10 



THE USE OF THE MICROSCOPE 



Causes of Injury. — (Continued) 



Cause 

 ■i2. Particles on screw 

 shoulders of sepa- 

 rable objectives. 

 43. Dust or film on back 

 of objective. 



44. Objective in wrong 



place on revolving 

 nosepiece. 



45. Objectives not cen- 



tered on nosepiece. 



46. Nosepiece with 



backlash. 



47. Inside of draw tube 



without dia- 

 phragm. 



48. Tube length not 160 



{or 170) milli- 

 meters. 



[49. Wrong Huyghe- 

 nian eyepiece. 



50. Wrong compensat- 



ing eyepiece. 



51. Smeared upper lens 



of eyepiece. 



52. Scratched upper 



lens of eyepiece. 



53. Film on interior sur- 



faces in eyepiece. 



54. Cemented compo- 



nents of some eye- 

 lenses separating. 

 55. Too low eyepiece 

 (too low magnifi- 

 cation). 

 56. Too high eyepiece 

 {too high magnifi- 

 cation). 



Injury 



Errors of centering, 

 mainly. 



Loss of light (dust), or 

 fog (film). 



More or less out of cen- 

 ter, causing injury to 

 image. 



One of the worst 

 sources of bad im- 

 ages and loss of light. 



One of the worst 

 sources of bad im- 

 ages and loss of light. 



Glare. 



Spherical and other 

 aberrations. A fre- 

 quent source of bad 

 images with high 

 powers. 



Slight aberrations. 



Chromatic errors, or 

 wrong tube length. 



Fog. 



Some loss of light, and 



diffraction. 

 Fog. 



Fog. 



Waste of aperture. 



Too large exit pupil. 



Curved field. 

 Empty enlargement. 



Too small exit pupil. 



Soft images. 



Preventive 



Avoid unscrewing, or 

 clean the contacts. 



Blow off dust, and re- 

 move film with lens 

 paper moistened with 

 distilled water. 



Screw in place marked 

 by maker. 



It is best to return to 

 the maker for repair 

 as soon as possible. 



Rotate nosepiece in the 

 correct direction. 



Insert a 14-millimeter 

 diaphragm below eye- 

 piece. 



Measure exact tube 

 length from shoulder 

 of objective to rim of 

 drawtube. 



Use parfocal eyepieces 1 

 made by maker of J 

 objective. 



Use parfocal eyepieces 

 made by maker of 

 objective. 



Examine often with 

 magnifier. 



Cover instrument to 

 keep off dust. 



Clean, and keep in 

 dessicator when out 

 of use. 



Avoid dropping eye- 

 pieces. 



Use lower objective, 

 and higher eyepiece. 



Use higher objective, 

 and lower eyepiece. 



