I have an Edge 8hd and recently ordered a zwo asi224mc (does not come with any extensions). My question has to do with mounting the camera with the proper back focus distance. The 8hd b/f distance is 133mm. I have the 8hd t-adapter (78mm). The asi224 has b/f of 12.5mm. So 133 - 78 - 12.5 = 42.5mm. The sequence I think I need is: telescope - hd t-adapter - m42-48 adaptor- zwo 21mm extension - zwo 21mm extension - ???? - asi224. This will get me to 132.5mm (counting the 12.5mm of the asi224) but not sure how or if the asi224 will screw into the back of the last 21mm extension. Do I need another 42-48 adapter between the last 21mm and 224? Does this chain make sense? Is there a better way to do this? Any input will be greatly appreciated.