NGC 2261 (LBN 920) Bright Nebula in Monoceros

Located at: RA 06 hours 39 minutes 10 seconds, Dec +08 degrees 44 minutes 52 seconds

Size: 2.0' x 1.7' Magnitude: -- Class: Emission + Reflection (variable)

North is up

West to the right

Telescope:

 14.5" f5 Newtonian reflector

Camera:

 ST-8XME, self-guided, binned 1x1, temp -20c, camera control MaxIm DL 4.56

Image:

Lumicon Red filter,  540 minutes (54 x 10 minute subs), 03/6/12/13/2014; seeing 2.6-5.0 FWHM per CCDStack

Processing:

CCDStack 2.77.5159.19820, Photoshop CS5.1

Location:

 Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s)

Notes:

I am posting three nights of imaging. A second night was not possible on the 7th, even though it was clear, as the moon moved too close for imaging, so I moved away from the moon to image NGC 2683. The second night (12th) had worse seeing, and more moon in the sky. Third night (13th) had a 95% moon rising in the east, but good seeing ... Still having periods of high clouds and wind (with poor seeing), but this object is bright enough for a decent image with this exposure.

NGC 2261 is also known as "Hubble's Variable Nebula", and is located about 47 minutes SSW of the 'Cone Nebula' (8" image) in Monoceros. Images taken over time show changes in the structure of this fan-shaped nebulosity. See the 8" version.

From the NGC / IC Project:

Contemporary Visual Observation(s) for NGC 2261

NGC 2261 = Hubble's Variable Nebula = LBN 920 = Ced 83 = R Mon = HH 39 = PP 64
06 39 10 +08 44.7
Size 2x1

13.1" (1/28/84): Hubble's Variable Nebula is bright, small, fan-shaped 2:1 N-S 
and widest at the north boundary.  The nebulosity tapers down towards 12th 
magnitude R Monocerotis at the south tip which appears to have a very small high 
surface brightness halo.  The western edge (oriented NW-SE) is slightly weaker 
and more curved than the eastern edge which is sharper and straighter N-S.  This 
is an impressive nebula with high surface brightness and interesting structure.

8": comet-like nebula extends from R Mon.

- by Steve Gottlieb
Historical Research Notes / Correction for NGC 2261
NGC 2261 is often called "Hubble's Variable Nebula" as its variability was 
indeed first noticed by Hubble during his years at Yerkes Observatory.  The 
nebula was discovered, though, by WH in 1783, and is the second of his new
class of "planetary" nebulae.  We know now that the nebulosity is actually
enveloping a very young double star system, R Monocerotis.  The star's 
variability was first noted by Schmidt (AN 55, 91, 1861).  The variability of 
the nebula is probably the result of circumstellar clouds close to the stars 
casting shadows on the surrounding nebulosity.  NGC 1554/5 (which see) around 
T Tauri is another example. - Dr. Harold G. Corwin, Jr.