PI Photography

Exercises in Extreme Focal Lengths
Minolta X-20 and Meade ETX-90

    Well, this is the most powerful of the optics tested - a catadioptic astronomical telescope set up for terresterial use. The Meade with a 24mm to 8mm zoom eyepiece gives you magnification of from 52x ( 24mm setting ) to 156x ( 8mm setting ).

    This was the most difficult to hold steady and with the camera merely held up to the eyepiece, not the images I want at all. And I won't recommend it be used without a sturdy connection for the camera to the eyepiece. Centering the camera lens on the scope's eyepiece is even more critical here due to the high magnification ratios possible. It seems it can be used, but I would like to get better images  before  I really say one way or the other.

    You get magnification by dividing the scope's focal length in mm by the size of the eyepiece in mm. In this case it is a 1250mm focal length ( f13.8 by the way - kinda slow for camera use - but can be used ). So … 1250 div by 24 = 52x.

    Remember – These were taken with a 2 megapixel camera ( 1600 x 1200 ).


    This is a camera shot alone - set at widest angle setting of 37mm equiv - 1x for here.

    Subject here is again close to 100yds.


    Now a shot at the longest zoom setting for the camera alone. Approx 111mm or 3x.


    Now I add the scope for 3x times 52x = 156x total magnification for this shot.

    1250mm div by 24mm = 52x
    52 times 3x = 156x
    156 times 37mm = 5,772mm
      in 35mm terms.

    And this is the  lowest  magnification possible using this eyepiece!


    This is a crop only ( no resizing ) of the above image at full size. It only gets bigger from here folks.


    Now I've bumped up the setting on the eyepiece to 16mm.

    1250 div by 16 = approx 78x
    78 times 3x = 234x
    234 times 37mm = 8,658mm
      in 35mm terms.


    This one is with the eyepiece set at 12mm.

    1250 div by 12 = approx 104x
    104 times 3x = 312x
    312 times 37mm = 11,544mm
      in 35mm terms.



    Final shot at full zoom - eyepiece set at 8mm.

    1250 div by 8 = 156.25x
    156.25 times 3x = 468.75x
    468,75 times 37mm = 17,344mm
      in 35mm terms

by the way …       
there is a doubler available
to use with this eyepiece !!

Copyright  ©  2005  ·  Barry A. Kintner  ·  Arizona Investigators Association  ·  A2Z Computer Works - Phoenix, Arizona