NGC 2237 – Rosette Nebula

 Date/time: 30.01.2009 18:50 to 30.01.2009 23:07
Az./Alt. positions: 116° / 27° to 193° / 44°
Ambient conditions: -5°C, transparency 5/5, seeing 4/5, exceptionally dry air
¼ Moon, Moonset at 22:00
Location: Trier, Germany

Equipment:
Telescope: TMB 92 SS f/5.5 with TSFlat, without dew heater
Mount: CGE, selfguided with ST-4000XCM
Camera: SBIG ST-4000XCM

Acquisition:
Software: CCDSoft V5
FOV, Image scale: 98.4 x 100.4 arcmin, 3.01 arcs/pixel
Sub-exposures: 3h 10min (19 x 10min) light frames at –35°C, 45 x 10min dark frames
30 x 1s EL flats at –35°C, 50 bias at –35°C for flats calibration

Processing:
Calibration, stacking and DDP in Images Plus 3.75,
curves and levels adjustments in CS3, noise reduction with Carbonis Actions,
GradientXterminator, green cast elimination with Pixinsight LE 1.0.

Comments:
Fantastic conditions for imaging, except for the present ¼ Moon and the street lights
at my observation site. In previous nights I observed that my self-made 32W dew heater was not
enough to avoid frosting of the telescope lense. Some instability of the stars had also been observed.
This time I experimented to insulate the dew cap with a 20mm thick Armaflex, with very good results:
10 hours imaging session without icing and with perfect stable stars.
To eliminate the strong light pollution gradient in the bottom of the image was very tough.