About one year ago we discovered that our 0.5m Cassegrain rooftop telescope can be used in prime focus mode, but until now I had little time to revisit a wonderful galaxy, M33.
There are many star forming regions visible in the Hydrogen alpha image (red in the image below), king of all being NGC 604, a nebula far larger than our familiar Orion Nebula.
Prime focus, 4 nights of imaging, RVBHa, about 2.5h per filter.
And the old, Cassegrain focus version, about 12h of exposure time in total, LRVBHa:
