NGC 2403 (Camelopardalis)

Object image
Fig.1 - One of the brightest non-Messier galaxies: NGC 2403 in the constellation Camelopardalis, photographed with a 16-inch f/4.5 Dob on an equatorial platform.
Object name: Constellation: Coordinates: Apparent size: Visual brightness:
NGC 2403 Camelopardalis 07h37m / +65°36' 23.4' x 11.8' 8.2 mag

The intermediate spiral galaxy NGC 2403 (also known as Caldwell 7) in the constellation Camelopardalis. NGC 2403 is a transitional type between the "spiral galaxies" and the "barred spiral galaxies" and contains numerous star-forming H II regions, one of the largest known H II regions being NGC 2404 in the northern spiral arm. The galaxy NGC 2403 is an outlying member of the M81 galaxy group and is approximately 8-10 million light-years from Earth. It is about 50,000-70,000 light-years in diameter and bears similarity to Messier 33. NGC 2403 was discovered by William Herschel in 1788 (source: Wikipedia).

Forty-one 3-minute exposures (122 minutes total exposure) at ISO 800 taken on December 18 / 19, 2020 were added for this shot with the DeepSkyStacker software and the final image processing was done in Photoshop.

Equipment: Canon EOS 450D Baader modified camera, TeleVue Paracorr Type II coma corrector, 16" f/4.5 "Ninja" dobsonian telescope riding on a dual-axis Tom Osypowski equatorial platform, Lacerta MGEN autoguider, Lacerta off axis system (field of view comparison: image of the moon with the same equipment).

H II regions
Fig.2 - Some of the brighter H II regions in NGC 2403. Annotations according to: Sivan, Petit, Comte, Maucherat. Optical HII regions in NGC 2403. Astron. Astrophys. 237, 23-35 (1990).
Search chart
Fig.3 - Search chart for NGC 2403. Map © 2020 "The Mag-7 Star Atlas Project", www.siaris.net. Map is slightly modified. The map can be downloaded here.