Why not a carbon tube and high quality focuser? Cost! This is not a cheap scope as it stands now. It has a rather unique optical architecture and the only production Mak-Newts in the same ball park are the Intes ones and they are more expensive. If the demand was there then it would be done. There is nothing wrong with the current tube, it does the job. The Intes Mak-Newts are heavier. Yes a carbon tube may save some weight, but in this design cool down won't necessarily be improved, and with widely spaced tube rings the stiffness if fine. I would suggest you buy an Orion fan that fit onto the rear fan mount perfectly, this aids cooldown times (no more than 30 minutes required, and remove the focuser plug so you get flow through).
Contact Ron at Moonlight and ask about an adaptor for the MN190. He is aware of the issue and I believe he may have one by now. The problem with the regular adaptors is that they did not provide enough fore and aft adjustment to allow the focuser to be centred over the corrector moutned secondary. Traditional newt secondaries sit on a spider which has some setback from the front ring, but with the MN190 secondary being mounted on the corrrector there is no spider or setback, so the focuser has to be centered further forward. The secondary also has a centre spot on it which is used to align it at the factory. The secondary centre spot is useful for collimation by the owner as well as your laser and the primary donut spot should be aligned with the secondary centre spot for perfect collimation. Don't ever touch the secondary offset on a MN190, it is factory set and I've found it to be perfect on mine.
PS I know Ron (Moonlight) has an adaptor for the Intes Micro Mak-Newts so the issues would be the same for those. It's worth asking the question. I don't have an issue with the stock focuser, so don't anticipate changing in the near future. I'll let someone else do the developement and testing, and proving it works for imaging before I change mine.
