NGC 7023 (Cepheus)

The bright reflection nebula NGC 7023 (Iris Nebula, Caldwell 4) in the constellation Cepheus

Fig. 1 - Clogged with cosmic dust: The reflection nebula NGC 7023 in the constellation Cepheus, photographed with an 8-inch f/4 Newtonian reflector on a ZWO AM5 mount.

Object name:	Constellation:	Coordinates:	Apparent size:	Visual brightness:
NGC 7023 (= Caldwell 4)	Cepheus	21h02m / +68°10'	18' x 18'	6.8 mag

NGC 7023 (Iris Nebula, Caldwell 4, LBN 487) is a bright reflection nebula in the constellation Cepheus. The nebula is filled with cosmic dust that scatters the light of the magnitude 7.4 star HD 200775. Its popular name comes from its resemblance in color photographs to the petals of a blue iris flower.

HD 200775, the central source of illumination in the Iris Nebula, is a Herbig Be star with an estimated mass of 10 to 15 times that of the Sun. Herbig Be stars are young, hot B-type stars that exhibit characteristic emission lines in their spectra and have not yet fully reached the main sequence. The star is only about 100,000 years old and emits large amounts of ultraviolet radiation, illuminating the surrounding dust clouds and shaping the complex structure of the nebula.

NGC 7023 measures about six light-years across and lies roughly 1,300 light-years from Earth. It was discovered by German-born British astronomer and composer William Herschel in 1794 (source: Wikipedia).

Technical Details:
Exposure time: 4h 30min (90x3min)
Gain: 100
Temperature: -10°C
Date: September 20/21, 2025
Processing: Astro Pixel Processor (APP) and Photoshop
Calibration: Darks, flats, and bias

Equipment:
Cooled ASI 2600MC Pro camera, TeleVue Paracorr Type II coma corrector, 8" f/4 "ONTC" Newtonian telescope, ZWO AM5 Strain Wave Mount, ZWO OAG-L off-axis system, ASI 174MM Mini guide camera, ASIAIR Plus

NGC 7023 was also captured with a 16-inch dobsonian on an equatorial platform, using a DSLR camera. The image can be seen here.

Ngc7331 M15