NGC7023 - Iris Nebula (Christopher Abissi)

NGC7023 - Iris Nebula

NGC7023 (Caldwell 4 and an open cluster, Collinder 427) also know ans the Iris Nebula is a reflection nebula which is embedded in a dust field. It is locate 1,400 LY distant appearing in the constellation Cepheus at Mag 7.7. Its apparent size is 8.0 x 10 arcmin. RA 21 hors 01.6 minute Dec +68 degrees 1 minute.

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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Distribution of astrophotographers

This table shows the number of distinct astrophotographers who have been assigned and IOTD/TP award compared to the total number of images awarded.
	Distinct awarded users	Total awarded images
Image of the day
Top picks
Top pick nominations

Distribution of subject types

This table shows the distribution of awards per subject type, compared to the popularity of images of that subject type.
	Image of the day	Top pick	Top pick nominations	Total submitted
Deep sky
Solar system
Extremely wide field
Star trails
Northern lights
Noctilucent clouds
Landscape

Distribution of data sources

This table shows the distribution of awards per data source, compared to the popularity of images acquired from that data source.
	Image of the day	Top pick	Top pick nominations	Total submitted
Backyard
Traveller
Own remote observatory
Amateur hosting facility
Public amaeteur data
Professional, scientific grade data
Mix of multiple sources
Other
Unknown

The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

Submitted The date and time when you submitted this image for IOTD/TP consideration.	...
Views by Submitters (available since September 19th, 2023) Every image is assigned to 50% of available Submitters. In the event that at least 80% of them don't view the image before its time in the IOTD/TP process expires, it's assigned to the other 50% of Submitters and the process begins anew.
Promotions by Submitters When 3 distinct Submitters promote the image, it moves on to the next stage of the process: evaluation for Top Pick status. This requirement, in addition to anonymization of images and distribution to only a subset of them, prevents biases and ensures that the best images are selected.
Promotions by Reviewers When 3 distinct Reviewers promote the image, it moves on to the next stage of the process: evaluation for IOTD status.
Early dismissal Staff members have a lot of images to inspect on a daily basis, and they can dismiss images if they believe they don't meet the requirements for IOTD/TP selection. If an image is dismissed 5 times, it's removed from the process. This streamlines the process and ensures that any bias present in promotions could be overruled by other staff members.

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