I bought and tested the entire TMB Planetary Type II line currently available. As with ALL eyepieces, one should not dismiss or praise an entire line based wholly on one single example and used in just one scope type. Contemporary EP designs can see a line designed for a refractor (convex focal plane), have some individual focal lengths perform not very well in Newtonians (concave focal plane), but there may be one, two or more individual focal lengths in that line up that will perform remarkably well in Newts! And these TMB Planetary Type II's are exactly like this. I tested these in an ED80 and an 8" f/4 Newt. This very fast Newt would very quickly show up the weakest performers in Newts, but you also need to remember that if used in a slower Newt, the performance of these would also improve.
All perform really well in scopes with a convex focal plane, ie refractors, SCTs and Maks, with the 6mm being the weakest performer (it was the weakest in the original TMB line up, and still the weakest when the Type II line was released). The 6mm is still usable, but I wouldn't recommend it nowb. In the 8" f/4 Newt, the best performers (sharp edge-to-edge is the definition I'm using for best performance here) were the 2.5mm, 4mm, 5mm, 7mm, 7.5mm & 8mm. I also got to compare the 2.5mm and 5mm with the very exotic 2.5mm and 5mm Pentax XO's. In a refractor, the XO's were outstanding which is to be expected as they were designed for refractors, and the TMB's performed just as well! In the 8" f/4 Newt, the 2.5mm XO was outstanding, as was the TMB, however, the 5mm XO was poor while the TMB was razor sharp across the whole FOV. Both of these TMB's were just as sharp and showed the same amount of stars as the much more pricey XO's. I won't be selling my 2.5mm or 5mm TMB's...
Of the other focal lengths, these still perform well in Newts, though the very edge does soften a little, but still usable. Just give the 6mm a miss.
Another great thing about these is the eye lens of all of these is the same BIG size with all of them, and the eye relief is the same generous amount also across the whole line - no need to park your cornea on the eye lens of the 2.5mm with this one! They also all have a 58° AFOV, which while somewhat modest is still way better than what a plossl gives.
Below is a pic of the TMB Planetary Type II's I tested. You'll notice that there are 14 eyepieces, and that's because I got four duplicates to test for QC.
QC is the weak link with these, unfortunately. Being made so fast, and sold so cheaply, assembly mistakes do happen, and of the 14 eyepieces I tested, three were unusable. The good thing though is if you get yours through Ebay and the EP is faulty, you can get your money back. Ghosting can be a distraction, but this is not to dismiss them outright. These are modest eyepieces after all, and somewhere along the line something has got to give.
For their price there is nothing that matches these. If $$$ need to be watched, or you just don't want to spend a lot of money on high power eyepieces, these are excellent value. Of the 14 I tested, I've kept 5 for my kit, the three duds are binned, and the others I did sell and now wish I had kept a couple of them...
And I still often use them with my lunar sketching as the focal lengths I've kept fill some focal length niches that can mean the difference between a productive night at the scope or watching TV. Are these as refined as say Radians? No. But for many people they will be just the ticket.
Alex.