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George Gearless

Aparently a T2 is not a T2 all the time

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I've run into a little problem with connecting my new camera to the telescope.

I used to use a Nikon DX40. And so I bought this coupling. If you click the link, you'll see that the description says "T2 thread". It fit perfectly and all was well.

Skywatcher T2 ring for Nikon DSLR

 

Then I bought a camera adapter, so I could insert different eyepieces/filters for planetary photography. Once again, you'll notice that the description says "T2 thread". It is not of the 'Skywatcher' make, but it fit the coupling as if it was made for it (picture below this paragraph). So far so good.

Omegon Camera adapter 1.25"

 

Recently I bought a Canon EOS D7 Mark-1. And naturaly I needed a new coupling. So I bought this Omegon T2-Ring, Canon EOS

Omegon T2-Ring, Canon EOS

 

It clicks snugly on the camera as expected. But the apperture with the internal T2 thread is much too big for any of the other stuff I have. 

So it begs the question(s): What the heck is T2 a reference to, since it apparently comes in different apperture sizes? And...how the heck can I ensure that my next purchase is the right one?

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The standard T2 adapter dates back to the late '50s / early '60s and was developed by Tamron for use with their lens range, hence the T. The standard thread size is M42x0.75mm but there is a recent DSLR adapter by Skywatcher which has a M48 thread to match their field flatteners / reducers.

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Looks like they have sent you the wrong one !!

They are available in M42 (T2) and M48 - put a ruler across the threads and see if its about 48mm across.

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19 minutes ago, Cornelius Varley said:

The standard T2 adapter dates back to the late '50s / early '60s and was developed by Tamron for use with their lens range, hence the T. The standard thread size is M42x0.75mm but there is a recent DSLR adapter by Skywatcher which has a M48 thread to match their field flatteners / reducers.

That answers my question as to the reference. Thanks Cornelius.

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1 minute ago, Skipper Billy said:

Looks like they have sent you the wrong one !!

They are available in M42 (T2) and M48 - put a ruler across the threads and see if its about 48mm across.

You know, it was niggling in the back of my head. I'll be sure to check up on it when I get back home with the callipers. Yes, I'm browsing the SGL forum while at work. I do some of my best research here...haha.

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Ugh, I've figured it out. I was too hasty.

I've discovered that there was an inlay ring (in lack of a better word) that has the appropriate aperture. That ring had fallen out of the main coupling, due to the three tightening screws not being tightened. This inlay ring serves as a M48 to M42 'converter'. So essentially the coupling came in two parts.

So I slipped this inlay ring into the main bajonet coupling and tightened the three screws to keep it in place. And voila! A perfect M42 thread for my camera adapter.

Sorry for wasting everyones time 😔  .

I'm not a smart man.

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