Operation Manual

35
EYEPIECE AND MAGNIFICATION OF THE TELESCOPE
Thepowerofatelescope’smagnification,whetheritisareflectororarefractor,isdeterminesby
thefocalwidthofthelensandtheeyepiece.Thefocalwidthisthedistanceofthelens,onwhich
asharpimageoranimageinthefocalpointisformed.Thefocalwidthofthelensisgenerally
quitelargeincomparisonwiththefocalwidthoftheeyepiece.Ifyoudividethefocalwidthof
thelensbythefocalwidthoftheeyepiece,theresultwillbethemagnificationofthetelescope.
Most astronomical telescopes need different focal width eyepieces for different strengths.
Theeyepieceswithshorter focal widths providealargermagnification.The strengthofeach
individualeyepieceisdirectlyrelatedtothefocalwidthoftheobjectivemirrorortheobjective
lensinthetelescope.
Theformulaisasfollows:
Focalwidthoftheobjective(mirrororlens)
  =magnification
Focalwidthoftheeyepiece
Forexample,yourH-12.5mmeyepiecewillshowamagnificationof:
800mm  700mm
  =64timesmagnificationor  =56timesmagnification
H-12.5mm  H-12.5mm
Magnificationtable:
eyepiece 4mm 8mm 12,5mm 20mm 23mm
 175x 85.5x 56x 35x 30x
erectinglens1.5x 262.5x 131x 84x 52.5x 45x

The eyepiece is inserted into the eyepiece bracket and by rotating the vernier knob, the
sharpening of the image takes place. Eyepieces are identified with letters, which determine
the model, e.g.“K” = Kellner, a triple lens system“H” = Huygen,“HM” = Huygen Mittenzwey,
“OR”=orthoscopicRamsden,“SR”=specialRamsden,“AH”=achromatic.Thenumbernexttothe
lettersshowsthefocalwidthoftheeyepiece.Ifyoucometooclosetotheeyepiecewithyour
eye,itcouldbecomedirtyfromeyelashesorfogupfrombreath.Cleantheeyepiececarefully
withasoftcloth.