Sh2-274, the "Medusa"
Ra 07h 29m 02.69s Dec +13° 14′ 48.4″
Image is in HST-palette, (HST=Hubble Space Telescope)
from the emission of ionized elements, R=Sulfur, G=Hydrogen and B=Oxygen.
Star colors are mixed from the NB channels, Red=H-a, G=O-III and B= 85%O-III + 15%H-a.
The Medusa Nebula is a large planetary nebula in the constellation of Gemini on the border of the Canis Minor. It also known as Abell 21 and Sharpless 274 (Sh2-274)
This nebula was thought to be a supernova remnant until early 1970, now it's known to be a planetary nebula.
Distance is about 1500 light years.
This has been the most difficult target to me to shoot by so far. The surface brightness of this, very diffused planetary, is reported to be between magnitude +15,99 up to +25!
Up here, at 65N, this target doesn't get very high and usually this time of the year is very cloudy. I started this project back in March 2010.
Natural color composition from the emission of ionized elements, R=80%Hydrogen+20%Sulfur, G=100%Oxygen and B=85%Oxygen+15%Hydrogen to compensate otherwise missing H-beta emission. This composition is very close to a visual spectrum.
Processing work flow:
Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack.
Levels, curves and color combine in PS CS3.
Equipments:
Telescope, Meade LX200 GPS 12" @ f5
Camera, QHY9 Guiding, SXV-AO @ 4,5Hz
Image Scale, 0,75 arcseconds/pixel
Exposures:
Baader H-alpha 7nm 5x1200s, binned 2x2
Baader H-alpha 7nm 5x1200s, binned 2x2 from previous session at January 12. 2011
Baader H-alpha 7nm 7x1200s, binned 1x1 from previous session at March 14.2010.
Baader O-III 8,5nm 3x1200s, binned 3x3
Baader O-III 8,5nm 1x1200s, binned 4x4 from previous session at January 12. 2011
Baader S-II 8nm 3x1200s, binned 4x4
EDIT.
There was some reflections in a O-III channel (Blue). I have fixed the channel now.
Special thanks to a "Bill W" from a "Cloudynights forum" to point this out.
0 comments:
Post a Comment