NGC 2170: Three Imaging Systems Combined

OTA: RH305 (f/3.8) RCOS (14.5” f/8) TOA150 (f/7.3)

Camera: SBIG STX-16803 SBIG STX-16803 FLI - ML16200

Location: New Mexico New Mexico El Sauce, Chile

EXPOSURES:

Red: 19 x 600 sec 21 x 1200 sec 21 x 900 sec

Blue: 19 x 600 18 x 1200 35 x 900

Green: 19 x 600 17 x 1200 24 x 900

Lum: 18 x 600 20 x 1200 26 x 900

Total exposure ~64.3 hours

Image Width: ~1/2 deg

Acquisition by DSW

Processed by Alex Woronow (2019) using PixInsight, StarNet, Gimp, Aurora HDR, Topaz, Matlab, SWT

NGC 2170 appears to be illuminated by a pair of sources: 1) Reflected light from young, hot stars causing the blue component. 2) Embedded young, hot stars ionizing the hydrogen and generating the red component. In much of the nebula these two components together contribute to the nebula’s color. Additionally, a complex dark nebula overlies part of the region, absorbing light and concealing the field behind it.

Processing: Combining the images resulted in over 64 hrs of exposure time! Although the fields-of-view varied greatly from instrument to instrument, all imaging systems reach or exceed ~1”/pixel resolution. This theoretical resolution exceeded the effective resolution, when factoring in ‘seeing’, putting all systems on a rather equal footing--as far as contribution to image detail.

The selected image-alignment mode produced a resulting field-of-view covering that of the RCOS imaging system, the narrowest coverage of the three imaging systems. Each system’s subframes were stacked individually, then mutually aligned, weighted by visual appraisal, and combined by color. The product RGB image was photometrically calibrated in PixInsight. The final image colors reflect this calibration. Structure of the cloud was enhanced in Matlab and PI, operating only the luminance channel, and the resulting L component imposed on the RGB. Various programs (see above) adjusted secondary color attributes such as saturation and radiance.