CHAMÄLEON + ONJALA OBSERVATORY DeepSky SITEMAP HOME CHAMÄLEON

« back to overview Star Clusters Load higher resolution (1800 x 1200 Pixel) Object description

NGC 6397 - a globular cluster in the constellation Ara

This image is the first test of Deep Sky Lucky Imaging at the CDK12 with exposure times of 1 s per single image. The used QHY 163M camera was kindly provided by Martin Miller for a test. A total of 900 1-second single images were taken in each color channel. The worst were sorted out and about 700 images per color channel were processed. The luminance channel was artificially generated from the RGB images to further minimize background noise. The finished image is therefore not a pure LRGB, but a (RGB)RGB image. Compared to images with 120 s exposure time, the seeing in the summed image improved from 2.5'' to 2.1'' (FHWM). The Moon, illuminated to about 80 %, was only 40 degrees away from NGC 6397 at the time of imaging. Due to the brightened background the weaker stars in the outer area could not be detected in this test. A second test image with ultra-short exposure times, the globular cluster NGC 6441, is shown here in comparison to a long exposed image..

Object description: NGC 6397 is the second closest globular cluster to our solar system after Messier 4. It is only 7,800 light years away and contains about 400,000 stars. It was first observed by Nicolas Lacaille in 1751. With a brightness of 5m7 it is visible to the naked eye under a dark sky. Due to the proximity to the solar system and the lack of intergalactic extinction, the distance of NGC 6397 could be determined very accurately. The average age of the stars was derived to 13.4 billion years, they are only slightly younger than the universe. « Click here or the thumbnail image for a comparison with the size of the Moon

Sun Moon Solar System DeepSky Widefield Miscellaneous Spec. Projects