Focusing Helicoids

• For trinocular heads lacking 38mm ISO photo ports,
  M42 focusing helicoids are my go-to parfocal camera solution.

• M42 10-15.5mm $19.99 + 1.50
  
  Used with Tc head on Nikon Metaphot.

• M42 12-17mm $19.50 + 1.50
• M42 15-26mm $19.49

• M42 17-31mm $23.99 + 1.50
  
  used with Optiphot 150/Eclipse (infinity) head

• M42 25-55mm $26.99
• M42 36-90mm $29.99 + 1.50
  
  used on American Optical 120 and EPIStar