| Diffuse
Nebula
NGC 6888, LBN 203 Apparent Diameter: 20' Minimum requirements to view: 8-inch telescope under very dark skies (UHC or OIII filters really help) |
The Crescent nebula has 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.
I tried and tried last year to see the Crescent in my 6-inch f/8 to no avail. In October 1999, 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 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.The above color image was created by combining red and blue second-generation DSS images.
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.
On 2000 July 3/4 I had the pleasure of observing NGC 6888 with Kemer Thomson's 18-inch Obsession from Mount Laguna. Without a filter the elongated white area near the center-top of the image above was clearly visible much as it appears in the image. 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 this filter 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.
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".
| Millennium
Star Atlas Vol III Chart 1149
Sky Atlas 2000 Chart 9 Uranometria 2000 Vol I Chart 119 |
