Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Is T/T2 mount the same as M42 thread mount? Fotodiox has another adapter for EOS but use the term M42
Document: Fotodiox did it again! This T-mount adapter is solid and feel professionally fabricated! It fits nicely on my 5D mark ii and has no light leak problem like some of the other available alternative on the market. Unlike the v2 Nikon to EOS mount that I have, this does not have play between the optics and the camera (that can also be because of the simplistic design of the t-mount themselves).Highly recommended for any photographer and videographer who are planning on resurrecting those vintage screw mount lenses!
I have a Meade ETX-60AT TELESCOPE. I wanted to shot the moon using my canon DSLR and the meade telescope. As the meade user's manual suggested, I purchased a T-adapter ring from meade (part no. 07366- #64ST- T-adapter) then screwed it in to the telescope.The Fotodiox 07LAtmeos T/T2 lens mount adapter (which I purchased from Amazon)is then screwed into the 07366 adapter. The Canon XS is then mounted. Every thing went well.
Great quality at a reasonable price. I use it to mount my Canon EOS 50D to my telescope adapter. Snug fit!
I have tried many similar EOS T rings. All of the others wiggled a little and never tightly snapped into the camera bayonet. Little problems like this can be big issues to the astrophotographer. The Fotodiox is not only the least expensive of all the options I have tried but by far it is the best fitting...nice tight fit, no slop or flexure.
The T-mount adapter is one of those items you need to keep in your photography tool bag. Unless you use a telescope or some of those weird third party lenses which need the adapter to mount to the camera body you will never use it. That being said, if you are a photographer you will find you can't live without it if you need one at a moments notice and don't have one laying around.As for this t-mount adapter, like all the other brands it is just a ring.
I have an old 500 mm catadioptric lens with a T mount that I used on my old film SLRs. I saw this adapter, and thought I could use it to make the old lens compatible with my Canon DSLRs. To an extent, it did work.It does make the lens compatible with the cameras. Given the 1.6x magnification factor, my lens became an 800 mm equivalent lens with a very shallow depth of focus.
It fit my Canon EOS T3i D600 perfectly, and screwed on my T-mount telephoto lens easily. A small jeweler's screw driver is needed to tighten the 3 set screws that allow the camera body to be rotated so that the lens F-stop markings will be on top when mounted on a tripod.
Fotodiox always has great fitting products and great prices. Just keep in mind that this is not everything you need to hook your DSLR to a telescope. You will also need a T-adapter.
I purchased this adapter for use with my kids telescope to take photos of the moon. If you want to connect your DSLR to a telescope then you will need one of these.The adapter is well made out of aluminum and goes on and off without issue. My T-Adapter fits perfectly and snuggly so there is no fear of my camera falling off.It comes packaged in a cardboard box which I threw away and just toss the adapter in my bag.
Simply, it is made of metal, it fits well, and is cheap.I bought one because I do use those weird third party lenses that need it.I mainly bought it for the telescope I am getting soon and just getting ready by making sure I have all the mounting hardware before I have the telescope.Only thing you really need to pay attention to for this product is to make sure it fits your camera body. This one fits Canon EOS, it won't fit on any other brand.
Answer: Close, but not the same. The T/T2 mount is threaded 42mm diameter X .75mm pitch. M42 is 42mm diameter X 1mm pitch threads. This link may help: http://en.wikipedia.org/wiki/T-mountThere are adapters to use M42 threaded lenses on Canon EOS cameras (google "M42 to EOS adapter"), if that is what you are looking for, but things like focusing will have to be done manually. I bought the Fotodiox T/T2 adapter to mount my EOS camera to an Orion universal camera to telescope adapter, and it works for that use.After receiving your email reply, yes it will work to count 10 threads and measure to determine what pitch you need, 1mm or .75mm. I also have a threaded 1.25" diameter tube that screws into my Fotodiox T/T2 to turn it into a standard telescope "T" mount. Both the T mount tube and the Orion adapter only have about 6 threads, so 10 are not available to make things easy!