WatchObservatory

I built one this summer (2021) and it works fine. You have to use a cold mirror because there will be internal reflections through transmission causing one or more ghost images, unless you pay lots of money for special anti reflection coatings. As for wavefront distortions, I got a science grade 80x50mm from Alluxa for 550$ USD delivered (2020 Oct) to Canada with 1/12 wave accuracy. Only down side is that it is 1mm thick, would have preferred more for strength. Here's my contraption (link below) - its going through trials, but main camera is flat across the entire field, guide camera doesn't show ghosts (but it is there) due to my DIY thresholding image star centroid app. Wit a 0.5x, the guide camera has the same field as the main, and very close to the same arcsec per pixel, no need to have an X-Y adjustment. I would not have used 3D printing because imaging train is heavy and I can't trust such on an 8K$ camera over time, at -25C, etc. http://watchobs.com/astronomy9.html Cheers