Hi Richard, I can see you’ve made progress since you first contacted me, it’s looking good! It’s fantastic what it’s possible to do from a back garden these days with relatively modest equipment – advances in low noise amplifiers and SDRs have really opened up radio astronomy. Basic averaging honestly does usually do a pretty good job with data like this, but you could try using a windowing function (something like hanning smoothing e.g. https://scipy-cookbook.readthedocs.io/items/SignalSmooth.html, or even just using a box function) can sometimes make peaks in spectral data look better by smoothing the noise more consistently. I’ve attached a copy of a figure from a book on radio astronomy that shows the whole galaxy in velocity as you look around the plane of the disk – you can see the spiral arms quite well here in the different clouds of gas moving with different velocity. The book is “An Introduction to Radio Astronomy” by Burke, Graham-Smith and Wilkinson – it’s an interesting read covering both the fundamentals of radio astronomy technology and some of the science that it can help with. Cassiopeia may well show up in your plots as there is a strong radio source in that constellation.
Richard Wilkinson