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NGC 1893 and IC 410
Open Cluster in Nebula
aka Melotte 33, Collinder 63, Raab 24, OCL 439 (Nebula is IC 410)
RA: 05h22m41.1s Dec: +3323'49" (Auriga)
Integrated Visual Magnitude: 7.8
Angular Diameter: 11.0'
Distance 13000 ly
Age: 10 Myrs

Minimum requirements to detect cluster: any telescope under suburban skies


NGC 1893 is another overlooked open cluster in Auriga.  The nebula it is embedded in, IC 410, is often photographed but rarely observed visually even though it is not that difficult.  Walter Scott Houston noted that NGC 1893 "contains a conspicuous Y pattern formed by four 8th magnitude stars."   He goes on to note reports that the cluster appears embedded in a haze of unresolved stars and suggests that the haze may actually be attributable to the surrounding IC 410 nebula.  In fact, IC 410 has been detected in telescopes as small as 12 inches without a filter and I was easily able to discern a faint, broad haze in my 18-inch.  But it is the availability of UHC and OIII filters in recent years that has really unlocked this treasure. 

In my 18-inch with OIII filter in place a large, diffuse haze became quite readily apparent.  The brightest region appears surrounding the stars that form the northwest portion of Scotty's "Y" (lower left in diagrams here).  A broad swatch of haze turns from here to roughly follow the pattern of stars southward, only to turn once again, this time to the east.  The result is a large, broad, Z-shape.  This shape can be seen faintly in the image here if you follow the whiter portions of the nebula, ignoring the deeper reds.  The H-Beta filter also brought out the nebula, but not as well as the OIII.  Others have reported easily seeing the nebula in a 10-inch scope with UHC filter in place.  I would not be surprised if the nebula could be detected in instruments as small as 6-inches from a dark site with a UHC filter. 

The stars of this cluster are all very young, having only been recently formed from the cloud complex that we see as IC 410.  In terms of the lives of stars these are all newborns, only 3 weeks removed from the womb.  In high resolution images two sets of gas streams can be seen in the northeast portion of the cluster.  The massive, hot, newborn stars of the cluster are literally blowing the gas and dust away from the region.  But the presence of a dense region of gas can block the wind leaving a gas "shadow" behind it.  These two "shadows" can be seen in the lower right of the image (enlarged in the image on the left).  I have not been able to find any observations of these streamers and was not aware of them when I last observed this region.  I wonder if they might be visible under higher magnification, perhaps with an H-Beta filter in place?

 


The field in an 6-inch f/8 at 50x.  North is down and east is to the right.
Millennium Star Atlas Vol. I Chart 114
Sky Atlas 2000 Chart 5
Uranometria 2000 Vol I Chart 97
Herald-Bobroff Astroatlas B-05 C-22