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Some many objective so little time (money)

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Some many objective so little time (money)

Postby Rob Watson on Thu Dec 14, 2006 12:09 pm

I have a Lomo P-111 with a phase contrast upgrade that uses the Q-Plan series objectives. The 100x will probably rarely (never) be used so I'm looking for a low power objective like a 2.5x or 4x that will be parfocal with the Q-Plan set I already have (10,20 and 40x). I will be using the low power mostly for bright filed and/or dark/oblique illumination modes.

What is the difference (besides N.A. and $) between the Lomo Flat field achromat, plan achromat and Q-plan achromat objectives? Are they all parfocal with each other (DIN) ?

I also have two objectives marked as TQA-2.5-1 and TQA-6.3-1 but I don't know which of the above lines they belong. I like the 2.5x but for the price the 4x plan achromat is pretty attractive. Any recommendations?

Also along these lines why would I want to use the compensating eyepiece instead of the noncompensating eyepiece?

Thanks so much
Rob Watson
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Postby on Thu Dec 14, 2006 1:00 pm


The only difference between Plan Achromats and the Flatfield Achromats is the field flatness. Plan Achromats have a flat field across the entire field of view. Flatfield Achromats have a 70-85% flat field depending on the magnification. It has nothing to do with the resolution of the image, only to field flatness.

You can use any DIN objective in a DIN threaded turret, but you must also have matcing focal lengths. Just because an objective is DIN threaded does not mean it can be used in any DIN threaded microscope. You cannot use objectives of different focal lengths at the same time because of clearance problems.

The TQAs are high grade Invertoscope objectives, but, again, you will need to use these together and not mix them with other focal lengths.

A compensating eyepiece is used when you are doing counts. A compensating eyepiece is guaranteed to give you an exact magnification when used with a specific objective to insure count accuracy. Otherwise, a non-compensating eyepiece will be close enough for general work.
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