Shot of the Month
Nasa expert ‘Mr Eclipse’ shares the steps behind taking this starry long exposure
A distant nebula in glorious colour
The Rosette Nebula in this image is a region of the sky that is too faint to see with the eye. Only with long-exposure astrophotography can its colourful beauty be revealed. It appears high in the sky on cold winter nights just to the east of the Orion constellation, so it is well-placed for imaging from my observatory in southern Arizona.
My telescope and monochromatic CCD camera weigh around 50 pounds, and are mounted on a German Equatorial mount that is carefully aligned with Earth’s axis of rotation. The telescopes, equatorial mount and CCD camera were all controlled from a desktop computer.
I shot 36 exposures through different filters, giving a combined exposure time of four hours. After individual images for this shot were acquired, they were calibrated to remove unwanted noise, as well as vignetting and dust on the filters. Calibration of images was with the scientific software CCDStack, with final adjustments in Photoshop. This image captures the glorious beauty and serenity of deep space in a location where new stars are being formed. In contrast, the petty squabbles here on Earth seem utterly insignificant in the grand scheme of things – a refreshing perspective that brings me great solace.
Fred Espenak received the Award for Scientific Imaging at the Royal Photographic Society Awards 2018