M42 mount vs T-mount for microscope adapter

Discussion in 'Accessories' started by philip_eastman, Mar 4, 2010.

  1. So I got this little portable microscope (www.looksmall.com) with an adapter that allows you to connect the scope's eyepiece to the body of an SLR camera to take pictures of magnified objects (I am using a Canon EOS 1000D). The adapter is 42mm in diameter, from which I gather I will need to purchase an appropriate mount to go in between my camera body and the adapter that connects to the scope.
    The problem is that I am having trouble figuring out exactly which type of mount I need. The manufacturer's instructions say the adapter "will require a T mount appropriate to the camera make; the T mount will have the correct bayonet/thread on the rear face to mate with the camera body and an M42 internal thread on the front face which mates with an M42 external thread on the adapter".
    From my understanding, a T-mount and an M42 mount are both 42 mm in diameter but the T-mount has a 0.75mm thread pitch while the M42 has a 1mm thread pitch, so the two are not interchangeable. Could someone please help me interpret the manufacturer's instructions? Am I correct that I will need an M42 mount and not a T/T2-mount? Thanks a bunch.
     
  2. You are correct.
     
  3. Yup, you understand T and M42 mount correctly. The problem is that the term "M42" only tells the diameter of the threaded mount but no thread pitch. Both T and M42 (a.k.a. Praktica mount) are actually M42 mounts.
    To avoid coufusion, the T mount should be described as "M42 P0.75" and Praktica mount, "M42 P1". If the manufacturer uses specifically the term "T mount", it should mean P0.75 which is popular among telescope adapters.
     
  4. You need a Canon EOS T2 mount. The front of this will have a 42mm T mount thread, and the other end will have an EOS bayonet mount.
    Hope this helps
    Alan
     
  5. Thanks for the info, folks. Thanks especially to Akira for clearing up the meaning of "M42".
     

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