Caldwell 46 — Reflection Nebula in Monoceros
NGC 2261
About Hubble's Variable Nebula
Description
Hubble's Variable Nebula (NGC 2261) is a small, fan-shaped reflection nebula in Monoceros, about 2,500 light-years away. It is illuminated by the young variable star R Monocerotis at its southern tip and shows remarkable changes in brightness and shape over weeks to months.
Observing Tips
Visible as a small, comet-shaped glow in a 4-inch telescope. The brighter southern tip and fan-shaped extension are distinctive. Compare sketches from different nights to detect variability. Best in winter evenings.
History
Discovered by William Herschel in 1783. Edwin Hubble studied it extensively between 1916 and 1920, documenting its changes. It was the first object photographed with the 200-inch Hale Telescope at Palomar in 1949.
Fun Facts
The nebula's variability is caused by shadows cast by dense dust clouds orbiting close to R Monocerotis, which block and redirect the star's light like a cosmic lighthouse.
Observe
1Properties
Position & Identifiers
2How easy to spot?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Hard+ | Hard+ | Hard |
| 150 mm Newton 150mm Newt. | Medium | Medium | Medium |
| Celestron C8 (203 mm SCT) C8 203mm | Medium+ | Medium+ | Medium |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
3Visibility
Set a location in User Settings to see visibility data.
4
Filter Response Guide
5
Eyepiece View
Hubble's Variable Nebula · 2.0′×1.0′ · N up, E left
Explore
6
Surface Brightness
Discover
7
Light Travel Time Machine
8
Relativistic Travel
Community Photos (1)
Credit: Judy Schmidt from Fresh Meadows, NY, USA. License: CC BY 2.0. (Wikimedia Commons)
Skybred Mar 2, 2026
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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