Date Posted: 7/28/2025
Date Taken: Four nights, from 11/4/2016 - 1/28/2017
Scope: Planewave CDK 12.5 f/8, 2541mm
Camera: SBIG STL-11000 with Astrodon Tru-Balance E-Series Gen2 filters
Temp: -15C
Mount: Losmandy Titan
Guiding: SSAG, Celestron 80mm guide scope, 600mm.
Exposure: LRGB 320:185:145:165 All subs 5min. Luminance unbinned, RGB binned 2x2.

Calibrated and Stacked with CCDStack2; Processed with CS4.

NGC 2403, also catalogued as Caldwell 7, is a bright intermediate spiral galaxy in Camelopardalis. It is the second largest member of the M81 galaxy group, ranking behind only M81 in size. As galaxies go, it is fairly close, with dinstance estimatesranging from 8-12 million light years. It was the first galaxy outside our local galaxy group in which cepheid variable stars were detected.

NGC 2403 contains numerous star-forming H II regions. The largest is catalogued as NGC 2404; it is approximately 940 light years in suze, making it one of the largest H II regions known. NGC 2403 is about 50,000 light years in size, and contains an estimated 80 billion stars.

This is a re-process of an older image taken in 2016-2017.