How to measure the 55mm spacing distance for the Baader MPCC mkIII?

[mikeyj1]

Having just acquired a coma corrector, my first outing with it showed - you guessed it - coma..  After a bit of research I understand the the corrector needs to have a distance of 55mm from the sensor (Canon 1300d).  but how to measure that?  i know the focal plane is shown on the camera body, but what about the MPCC?  near side of the element? mid point?... 

Also, I have one 'T'ring spacer, which screws onto both the mpc, if i remove the knurled ring, and the camera t ring.  Anyone know where to get other spacers like this? ( a link would be great  )

thanks 

Mike

[Tim]

Usually the rear flange on the MPCC. Should be about right screwed into your camera T ring I would have thought.

What is the spacer, M48 front, M42 rear thread? I dont think you will need it for spacing, but if the MPCC does t screw right into the t ring, get a t ring that will. 

[michael8554]

The Canon sensor is 44mm from the lens flange, so you need 55-44 = 11mm of spacing, which is often the T2 ring thickness as Tim has already posted.

Michael

[mikeyj1]

thanks both, The T2 adapter i have isnt an M48 version, its M42, but i can see that the distance from the focal plane would be almost exactly right to the back of the MPCC thread, as suggested. The spacer is M42 male to M48 female,  So i need a T ring with the right thread only, preferably cheaper than the Baader one, although I suppose there will be no doubting the quality i did go that way

cheers

Mike