Dark Horse Observatory

Dark Horse Observatory
Kimberton, PA US


Image Details: NGC 7023 (Caldwell 4) & Collinder 427

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NGC 7023 (Caldwell 4) & Collinder 427

Object/Name: NGC 7023 (Caldwell 4, Iris Nebula) Image Details:
Type: Diffuse Nebula (reflection) Luminance IRB:5.00 min. (43) – 215.00 min. 1x1
Constellation: Cepheus Red:5.00 min. (14) – 70.00 min. 1x1
RA: 21 hours 01.6 minutes Green:5.00 min. (15) – 75.00 min. 1x1
Dec: +68 degreees 1 minutes Blue:5.00 min. (15) – 75.00 min. 1x1
Distance: 1,400.0 light years Total Time:435 minutes
Magnitude: 7.7 mag   
Size: 8.0 x 10.0 arc minutes   
Imaging Dates: 21 September - 13 November 2007   
Location: Dark Horse Observatory, Kimberton, PA 19460 U.S.A.   
Telescope: Takahashi BRC-250 Mount: Mountain Instruments MI-250
CCD: SBIG ST-10XME Rotator: Optec Pxyis Rotator
Focuser: Finger Lakes Instruments DF2 Filters: Astrodon Series E
Software Used:
  CCDStack MiraPro Professional
Photoshop CS2 Russel Croman’s Gradient Xterminator
Noel Carboni’s Astronomy Tools  
Detailed Information:
NGC 7023 was observed 18 October 1794 by William Herschel. It is located about 3.5 degrees south west of Beta Cephei (Alfirk). This is a wonderful example of a reflection nebula. Its unusual structure gave rise to the name, the Iris Nebula. The nebula is illuminated by light for a Mag 6.8 star (HD200775) in its center. The bright blue light seen here is due to light being reflected off dust particles that survived the star's birth. There are faint hints of red color surrounding the central star. This is evidence of some hydrogen emission taking place. Images of this object frequently capture the dense dust cloud that is resides in.

There is also and open cluster of stars associated with NGC 7023 that is known as Collinder 427. This loose open cluster is located on the west side of the reflection nebula within the dark region above the "petal" structure of the Iris. There was a second cluster reportedly within the nebula NCC 7023 cataloged by Collinder as 429, but this was a mistake as there is no other open cluster within NGC 7023. SIMBAD erroneously attributes the cluster to van den Bergh (Cl vdB 139) while van den Bergh himself gives no mention of a cluster near the reflection nebula. The object vdB 139 is NGC 7023.

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