Tuesday, Apr 8, 2025

NGC 2403 is a very beautiful galaxy in the constellation Camelopardalis, whose appearance resembles that of the Triangulum Galaxy (M33). Due to its distance of approximately 8 million light-years, it appears smaller in comparison, but it is actually significantly larger than M33, which is about 2.7 million light-years away. Thanks to five clear nights in a row, I was able to collect a total of just over 30 hours of exposure time with my f/5 Newtonian telescope at 950mm focal length—split into 23.5 hours of RGB and 6.5 hours of H-alpha. The H-alpha data was carefully integrated into the image after continuum reduction to ensure it does not dominate the entire composition and disrupt the overall impression. Here are some additional details about NGC 2403: NGC 2403 (also known as Caldwell 7) is an intermediate spiral galaxy in the constellation Camelopardalis. It is an outlying member of the M81 Group, and is approximately 8 million light-years distant. It bears a similarity to M33, containing numerous star-forming H II regions, but being a little bit larger at approximately 90,000 light-years in diameter compared to the 61,100 light-year diameter of M33. The northern spiral arm connects it to the star forming region NGC 2404. NGC 2403 can be observed using 10×50 binoculars. NGC 2404 is 940 light-years in diameter, making it one of the largest known H II regions. This H II region represents striking similarity with NGC 604 in M33, both in size and location in galaxy. –Wikipedia