Waid Observatory

Object: Abell 21 - The Medusa Nebula

Date: Nov. 28/29/30, 2022   -    Location: Davis Mountains west of Fort Davis, TX
Telescope: 10 inch RC    -    Mount: Paramount MX   -  Camera: Apogee Alta F8300M
Exposure: Ha = 17x20 min. OIII = 18x20 min  Bin 1x1  R,& B = 20x5 min G = 19x5 min  Bin 2x2

Click on the image to view at higher resolution.

Abell 21

Abell 21 - The Medusa Nebula

Abell 21, communally known as the Medusa Nebula(1), is a planetary nebula in the constellation Gemini(1) approximately 1500 light years distant(3).  Serpentine filaments of glowing gas resemble the hair of the mythological Medusa(3).  The nebula was originally discovered in 1955 by astronomer George Abell(2).  Until the early 1970s the nebula was considered by many astronomers to be a supernova remnant(2).  In 1971 Soviet astronomers concluded Abell 21 was most likely a planetary nebula(2).

The image above was captured using Ha (Hydrogen Alpha) and OIII (Doubly Ionized Oxygen) narrowband filters.  The image was assembled by mapping Ha to red and OIII to green and blue.  The stars were overlaid with RGB filtered data to give them a near true color appearance.

1Wikipedia: https://en.wikipedia.org/wiki/Medusa_Nebula
2Brendan Kinch - https://www.kinchastro.com/abell-21-2020-madusa-nebula.html
3NASA APOD - https://apod.nasa.gov/apod/ap220325.html

Copyright Donald P. Waid