That's very impressive. A couple of question pls....
1. What is the model number of the Tamron 135/28, I'm look for something similar.
2. What was you final effective aperture before you got rid of the come?
This was the lens itself:
Wide open the aperture is 48mm (simply based on 135/2.8).
With the 37mm ring it was operating at F3.65 (135/37).
The homemade ring was, I believe, 24mm, which gives about F5.6.
So not a lot of aperture compared to something like the Samyang 135 (which at F2.8 would have 48mm of clear aperture). But with an EQ mount I should hopefully have no probs just shooting longer subs to compensate (albeit with reduced resolution, but hey for £20 I can hardly complain!).
I still need to use the lens properly though, so I can't say how it perform at this F-ratio just yet.
For giggles, if you want to see what the homemade ring (made in a mad rush as it was already late and I was wasting clear skies) then have a look here