Large emission nebula with the watec Version 27. August 2003
Martin Elsässer

For some nights now, we have tested the visibility of faint, large nebula in the live image of the new watec-camera. Existing experience with the mintron under good observing conditions showed a wealth of milky-way features.

From our observing location, only 15km from the center of munich, a city with 1.5million people, the night-sky is quite bright, with the milky way just visible on the best nights. For the watec this sky brightness is fatal, when using optics with a large aperture setting. With the used optics, a surplus lens from a military night-vision device, f=25mm, f/D=1.1, this sky brightness results in a completely saturated, white image. With the use of a h-alpha filter, the sky brightness could be reduced and the contrast enhanced, to produce usable images.

The used optics has severe scratches on the front lens and was used without an extra shield against the surrounding light sources. The edge of the illuminated building to the north is visible in most images and caused severe glow across some images. With further tweaking of setup and location better results will be acchieved. Some more experiments with proper processing will follow.

The amount of nebulosity visible in the live image was amazing: North America nebula, Pelican-Nebula, Cirrus nebula, IC1396 and such were easily visible. Even fainter structures like the Horsehead Nebula and Barnards-Loop were directly visible. The short focal length does not require a tracking mount, a simple photo tripod was sufficient.

To demonstrate these capabilities, we captured and added the images delivered by the watec. Each object is shown in two versions:

1. averaged images

Just averaging all the images, but without enhancing brightness or contrast. This resembles what is visible to the observer in the live-image, if patience and good mental-noise-reduction is applied.

NGC281, the packman nebula
NGC7000, the north-america-nebula
Cirrus nebula, not really ideal for h-alpha
Nebulosity around Gamma Cygni
IC 1396
IC 1396, another set of images
IC 1805
M31, though h-alpha does not really make sense here
Orion-nebula, barnards-loop, horsehead-nebula

2. contrast enhanced sum of images

A contrast enhanced version of the summed-image, without using darks or flats was created. Though the appearance of these images is far from perfect, a large amount of faint detail can be seen. On average, 120 images per object were used for these images, resulting in 20 minutes total exposure time.

NGC281, the packman nebula, the nebulosity around gamma cassiopeia can be seen to the right
NGC7000, the north-america-nebula, pelican nebula, and lots of other nebulosity
Cirrus nebula, not really ideal for h-alpha, but still all parts visible
Nebulosity around Gamma Cygni, Cocoon nebula, several others
IC 1396 and additional nebulosity
IC 1396, another set of images
IC 1805, well visible though affected by the reflected glow of the building
M31, h-alpha does not really make sense here
rosette-nebula and additional nebulosity
Orion-nebula, barnards-loop, horsehead-nebula, nebulosity everywhere, just a photo-tripod