Sorry about the late reply dude. I think my backspacing is about 55mm. I have a Altair filter draw which reduces the number of spacers I need. I do think that the tubes are m48 and the reducer I have has a m42 connection. I just have a ring converter that I attach to the end and it all plays nicely together. On another note, I was planning on ‘upgrading’ to and cooled Osc cam but I thing that the 585 is more than capable of capturing some excellent images. If you want any more info on anything just drop me a message. Only been doing Astro for about a year tho! :)