M 27 - Dumbell Nebula

Date/time: 23.08.2008 22:00 to 23.08.2008 23:00
Az./Alt. positions: 168° / 62.5° to 198° / 62°
Ambient conditions: 10°C, transparency 4/5, seeing 3/5, ½ Moon, Moonrise at 22:00
Location: Trier, Germany

Equipment:
Telescope: Celestron SC 8” with focal reducer Alan Gee at f/6
Mount: CGE
Guiding: Manually through a A&M 60mm finderscope
and a Philips webcam SPC 9000 NC with a 2X barlow
Camera: SBIG ST-4000XCM

Acquisition:
Software: CCDSoft V5
FOV, Image scale: 43.4 x 43.4 arcmin, 1.27 arcs/pixel
Sub-exposures: 60min (6 x 10min) lights at –20°C, 16 x 10min darks,
16 x 0.03s light box flats at –10°C, 50 flatbias at –10°C

Processing:
Calibration with darks and bias normalized flats, Min/Max Exc Avg stacking,
DDP, white point adjustment and neutralized background in Images Plus 3.0.
Curves, Levels and sharpening in CS3.
Noise reduction with Carbonis Actions under CS3.
Image cropped vertically to minimize visible sky gradient.

Comments:
Object at high altitude favored the acquisition, even with the rising half Moon.
Most vignetting from Alan Gee reducer could be removed by the flats. Alan Gee used
with two spacers inserted in the SC back tube provides ideal spacing reducer-CCD,
but the JMI focuser in this configuration cannot be used.