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The Crescent Nebula
Diffuse Nebula
NGC 6888, LBN 203
Apparent Diameter: 17' x 9'

Minimum requirements to view: 8-inch telescope under very dark skies (UHC or OIII filters really help)

The Crescent nebula had long been an object of my desire. This faint, arcing diffuse nebula appears in one of the most beautiful fields of the summer Milky Way, about 2/5th of the way from Gamma to Eta Cygni. Catalogs list it as 10th magnitude but I found it to be much more difficult than this would imply.

The above color image was created by combining red and blue second-generation DSS images. 

I tried and tried one year to see the Crescent in my 6-inch f/8 to no avail. When I finished my 18-inch f/4.5 Dob, this was  my first serious target. I was rather disappointed when I failed to see the nebula with my new scope on several different nights. Since then Skyhound 18 and I have gotten to know each other much better. We've successfully observed some very faint objects. On the night of May 30/31 I was very, very careful with my dark adaptation and conditions were quite good. I believe that it was my experience with the scope and the confidence this brought that made the difference in my eventual success.

This nebula makes an arc among several bright stars. I was able to detect the nebulosity on the northeast side first. Eventually I found the curving haze to the southwest. With time and averted vision I was able to make out the entire arc of the nebula.

One July I had the pleasure of observing NGC 6888 with Kemer Thomson's 18-inch Obsession from Mount Laguna. At the time he had an advantage over me: a wider field eyepiece.  The wider field made a big difference. The elongated white area near the center-top of the image above was clearly visible much as it appears in the image. Filters made an even bigger difference. With a UHC filter the rest of the nebula appeared, looking very much like the image (without the colors). The best view was with the OIII filter which greatly increased the contrast. With the OIII in place the faint wisps in the center filled the nebula into a complete "pear."

Without a filter it is essential to observe this object with a wide field eyepiece.

The field in a 12-inch LX200 with a Widefield 40mm eyepiece (76x).

A UHC or OIII filter  may be necessary to view this nebula in scopes smaller than 8-10 inches. AJ Crayon writes, "In my 8 inch f6 at 60X the nebula was about 15'X5' in a northeasterly PA with a larger northeastern side.  On this particular night the nebula was of uniform brightness and the famous crescent shape appeared pear like with several stars involved.  Yes, pear like!"

Don Pensack writes:

Appeared "ear-shaped", relatively bright, no filter necessary at ~200x. Brightest section appeared to be the Ear outline, with 10-20 irregular tufts of nebulosity scattered across the face.  A much fainter outline completed the "pear" mentioned. With a UHC filter, the lines resolved into intertwined filaments similar to the Veil Nebula, though the particularly abrupt reduction in the number of field stars made the sight less pleasing.  With the UHC filter, the general outline became sharper, and the filaments seemed to "writhe" across the field as even fainter nebulosity came in and out of view. I've seen this object in 6", but the amazing amount of detail visible in 20" makes this up there with the Veil as a "showpiece".

In smaller instruments this is a challenging object to detect.  But in larger scopes the Crescent becomes a showpiece, particularly when an OIII filters is employed. 

Millennium Star Atlas Vol III Chart 1149
Sky Atlas 2000 Chart 9
Uranometria 2000 Vol I Chart 119